HUI LING CHUN v. SHIU MAK YING AND ANOTHER

DCCJ10294/2001

IN THE DISTRICT COURT OF THE

HONG KONG SPECIAL ADMINISTRATIVE REGION

CIVIL ACTION NO. 10294 OF 2001

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J U D G M E N T

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Introduction

1. The Plaintiff ("P") as owner of Unit No.2 on 4th Floor, Hung King Court (Block F), No.102 Baker Street, Hunghom Bay Centre ("HB Centre"), Kowloon, Hong Kong ("4/F Unit") claimed that there was water leakage to 4/F Unit from the unit directly above on the 5th Floor ("5/F Unit") owned by the Defendants ("D") constituting nuisance and/or breach of the deed of mutual covenant and/or negligence on D's part. P therefore prays for an injunction against D to rectify the water leakage and for damages. D denied that the water leakage came from 5/F Unit.

Preliminary matters

2. There is no presumption that the water source necessarily came from the flat above. P has the burden of proof to show that the source of water came from 5/F Unit (張秀玲及吳炳漢及鄭禮莊CACV268/98 (unreported, 9th April 1999) and Leung Yung Chun & anor v Chan Wing Sang & ors [2000] 1 HKLRD 456). It is not for D to find out the real source of the water leakage or to prove that its origin did not come from 5/F Unit.

3. P's husband Mr Poon Chi Hung ("Poon") and her expert Mr Stewart Wong ("Wong") of Proficient Surveyors & Co ("Proficient") gave evidence. Mr Choi Chun Hoi ("Choi") gave evidence for D, who also called Mr Lee Chun Fat ("Lee") of Lee Mark Building Surveyors Limited ("Lee Mark") as their expert witness. There is no dispute as to Wong and Lee's expert capacity, but the relevance and depth of their expertise on the core matters of the present case are in issue.

Poon's evidence

4. Poon and P occupied 4/F Unit since 1980. In early 1999, Poon noticed a 2-inch water stain on the ceiling ("4/F Ceiling") in the toilet ("4/F Toilet") above the washbasin which gradually spread with loosening, blistering and peeling of plaster. An old couple from 5/F Unit suggested it was condensation from bath-taking. 2-3 weeks later, Poon reported to the manager of HB Centre, Whampoa Property Management Limited ("Manager"), who by letter dated 3rd February 1999 to D suspected the floor slab and outlet drains of the toilet of 5/F Unit ("5/F Toilet") were the cause and urged D to carry out repairs.

5. D took no action, so Poon in late January 1999 approached the Food and Environmental Hygiene Department ("FEHD"). FEHD carried out a colour water test ("CWT") on 23rd April 1999 ("1st CWT") using Orange II, Fluorescein sodium, Eosin yellowish and Sulforhodamine B ("FEHD Dyes"). The government laboratory ("GI") detected no colour dye from the plaster sample collected from 4/F Ceiling on 11th May 1999. FEHD eventually wrote to Poon on 8th December 2000 to say that the cause of the water seepage could not be ascertained.

6. The matter was referred to the Water Supplies Department ("WSD") and Buildings Department ("BD"). WSD reported on 30th June 1999 no damaged water pipe or water leakage at 5/F Unit was found, so repairs were inappropriate, but Poon should liaise with the occupants of 5/F Unit to engage a licensed plumber or qualified person to investigate. BD reported on 8th July 1999 that they found no structural danger but would urge D to take measures to stop the water leakage.

7. D took no action despite the Manager's letters of 11th September 1999 and 3rd November 2000. It was noted in the former letter that D had replaced the bathtub at 5/F Toilet with a shower cubicle ("Shower Renovation"). Poon also knew D replaced the original floor and wall tiles of 5/F Toilet with large ceramic tiles ("Tiling Renovation", which together with Shower Renovation are collectively known as "5/F Toilet Renovation").

8. After an inspection by Wong by the end of 2000, he concluded in his 1st report dated 27th January 2001 ("Wong's 1st Report") that 5/F Unit caused the water leakage. P's solicitors demanded D to carry out remedial works, but D only pressed for full disclosure of Wong's 1st Report, which P subsequently did pursuant to a court order. Under another court order, Wong and Lee jointly inspected 4/F and 5/F Units and Wong prepared his 2nd and 3rd inspection reports dated 11th March 2002 and 28th September 2003 ("Wong's 2nd and 3rd Reports"), which confirmed his earlier finding.

9. The water leakage deteriorated between the time of Wong's 1st and 2nd Reports with expansion of the affected area and slow water dripping from where the metal rail joined the beam of 4/F Toilet ("4/F Beam"). Poon could not remember how long it took to collect 2 bottles of water from the slow dripping. The dampness spread to the ceiling of the living room just outside 4/F Toilet and the master bedroom ("Master Bedroom"), not the guest bedroom ("Guest Bedroom"). Improvement was observed 2-3 months before the trial as the dampness no longer expanded and there was no dripping water.

10. Poon knew that pink/orange colour appeared at 4/F Ceiling (which Wong opined was from FEHD Dyes) and that D asked for plaster sample from 4/F Ceiling to be sent to FEHD for re-testing. Poon refused as FEHD required him to re-start the investigation process, which would be time-consuming.

11. The water leakage (which did not abate during the dry season) was not caused by rainwater seepage through the external wall ("External Wall Cause") of Block F of HB Centre ("Block F"). Renovation of HB Centre ("Building Renovation") included renovation of the external wall ("EW Renovation"), which Manager told Poon was completed in May 2002. Given the then good weather and completion of EW Renovation, Manager thought that the possibility of External Wall Cause was small. The external wall of some units (but not 4/F Unit) still had water seepage despite completion of EW Renovation. Manager suspected the water leakage came from 5/F Toilet and urged D to engage a licensed plumber to investigate the concealed pipes in the floor slab of 5/F Toilet ("Floor Slab").

12. Poon and P found the water leakage a disturbance and nuisance over the years. Water dripped on Poon when he bathed and onto his bed in Master Bedroom, so he had to shift his bed. Poon relied on Wong's recommendations on the remedial measures for 4/F Unit when the water leakage ceased.

Choi's evidence

13. Choi and his family (4 persons) resided at 5/F Unit (which had been renovated twice) since 1986. There was no change in usage of 5/F Toilet since the last renovation in 1996 (ie 5/F Toilet Renovation) carried out by a qualified contractor ("Contractor") with a water test done on Floor Slab upon completion. Choi was satisfied with Contractor's workmanship.

14. When P complained of water leakage in early 1999, Contractor thought it unlikely that any problem from 5/F Toilet Renovation would take 3 years to surface. Upon inspection of 4/F Toilet, he opined that the slight water stain and peeling plaster were probably caused by condensation and lack of maintenance. P refused his suggestion to re-plaster and re-paint 4/F Ceiling (so any future leakage would be shown to be a genuine problem).

15. D allowed FEHD to carry out 1st CWT at all outlet drains of 5/F Toilet (the cistern ("Cistern"), Floor Slab for dye water to pass through the floor drain ("Floor Drain"), the whole of the shower cubicle and the washbasin ("Test Areas")) with different coloured dye water. FEHD informed Choi in June 1999 that the plaster sample taken on 11th May 1999 showed no colour dye. On 29th July 2003, FEHD confirmed to D's solicitors that "the cause of water seepage could not be ascertained within the means of this Department".

16. In June 1999, WSD inspected 5/F Unit including its fresh water supply pipes ("FWS Pipes") at 5/F Toilet and kitchen and carried out a water pressure test ("WPT") but did not find any water leakage or damaged water pipes ("1st WPT"). BD did not contact Choi but D would have co-operated had BD done so.

17. Choi had fully responded to Manager's letters, except for the letter of 3rd February 1999, which he did not receive, but by that time, he had asked Contractor to look into P's complaint. Choi told Manager of FEHD and WSD's findings. Manager did not carry out any tests.

18. On 20th November 2000, Choi received a demand letter from P's solicitors to stop the water leakage, but he denied liability through D's solicitors. In December 2000, D allowed Wong to inspect 5/F Unit. On or about 15th March 2001, P's solicitors wrote to D and their solicitors enclosing findings from Wong's 1st Report and demanding compensation of HK$30,000.00.

19. Wong said the light orange matter found in the plaster sample from 4/F Ceiling collected by him was from FEHD Dyes and therefore concluded that the water leakage came from 5/F Toilet. On 23rd April 2001, Choi through solicitors suggested to P to invite FEHD to re-inspect 4/F Toilet and promised to carry out remedial measures if it were confirmed by FEHD that the water leakage came from 5/F Unit. P issued the present proceedings without giving any reply. P also refused D's proposal through solicitors on 17th August 2001 for a joint independent survey. On 24th November 2001 D through solicitors repeated the suggestion of allowing FEHD to take plaster sample or alternatively sending Wong's plaster sample to FEHD for analysis, which P again refused. As P only gave D certain extracts of Wong's 1st Report, D successfully applied to the court on 6th December 2001 for the full report and for an order for joint inspection by both parties' surveyors.

20. On 27th December 2001, Lee carried out CWT at 5/F Toilet ("2nd CWT") in Wong's presence, which produced negative results. Lee's inspection report dated 24th April 2002 ("Lee's 1st Report") excluded 5/F Unit as a cause of the water leakage. Since Wong's 2nd Report maintained otherwise and alleged leakage from connections of FWS Pipes concealed in the concrete walls of 5/F Toilet, Lee carried out WPT on 17th May 2003 ("2nd WPT") which produced negative results, and he concluded in his inspection report dated 20th May 2003 ("Lee's 2nd Report") that there was no water leakage of FWS Pipes of 5/F Unit.

21. Choi denied that D carried out patch repairs by applying sealant to 5/F Toilet 2-3 days before Wong's inspection for Wong's 3rd Report. Any differences discerned in the photographs in Wong's 2nd and 3rd Reports were due to the use of different cameras, angles and distances. The sealant appeared clean because of vigorous cleaning during SARS outbreak from March to May 2003. Even if the sealant were recent patch repairs as alleged, it could not have caused the reduction of water leakage observed by Poon 2-3 months before the trial.

22. Choi also denied that D replaced the valve of the flushing system ("Flushing Valve") of Cistern and explained that photographic differences might have given rise to this misunderstanding. Choi also denied that there were darkened water stains on the teak parquet flooring at Master Bedroom, which flooring had not been replaced for 20 years. The dark spots found at corners or doorframes were due to difficulty in cleaning and similar dark spots could be found near to the main entrance where there was no water source. Choi agreed that on 23rd May 2003 white sealant (not the old transparent sealant found at 5/F Toilet) was applied to the wall skirting which had become loosened and to where the doorframe and the teak parquet flooring were joined. The cracks on the beam of 5/F Toilet ("5/F Beam") were caused by expansion of the internal reinforcement.

23. Lee's 1st Report and his inspection report dated 25th September 2003 ("Lee's 3rd Report") suggested that one possible cause of the water leakage was External Wall Cause. Choi recalled discussion/consultation in 1997 and 1998 by the incorporated owners of HB Centre ("IO") and Manager about such problem. IO commissioned survey reports from Raymond Chan Surveyors Limited ("RCSL") in August 1997, January 1998 and September 1998 ("RCSL's 1st, 2nd and 3rd Reports", collectively "RCSL's Reports").

24. RCSL's Reports revealed substantial defects of the external wall of HB Centre, eg 97% of the tiling system was defective. Choi said this applied to Block F because Block F's owners did contribute to the cost of Building Renovation. The defects were not restricted to the roof for otherwise EW Renovation would be unnecessary. Appendix F of RCSL's 1st Report which set out "reported" water leakages at HB Centre referred to certain instances where RCSL considered that water seepage at certain units (not 4/F Unit) was due to the external wall.

25. RCSL's 2nd Report showed 71% of responses from HB Centre owners ("Responses") (188 flats) had water leakage through the external wall, mostly at the bedroom and some at the toilet. 60% of Responses (159 units) had water leakage at the ceiling and of those 64% was at the toilet. 52% of Responses (138 flats) had pipework problem, mostly in the toilet. Although RCSL's 2nd Report suggested owners might wish to replace internal pipework in line with Building Renovation and apply mastic sealants around inter alia sanitary fitments to reduce leakage, Choi said they were a matter of owners' choice and did not necessarily show problems existed at the relevant flats.

26. RCSL's 2nd Report concluded that water leakage problem was due to defects of the external wall, such as defective tiling, detailing and cracking. Choi said IO carried out EW Renovation from about June 2001 to October 2002 but they were for the less comprehensive option of making patch repairs to defective areas identified by hammer tapping test and covering with tile filler and re-painting. This might not address all defects in the external wall. Manager's letter of 15th March 2002 only stated that tile filling of Block F's external wall had been completed, but re-painting had not been done, so EW Renovation was only completed subsequently.

Preliminary assessment of the factual witnesses

27. It is not disputed that 4/F Unit had suffered from water leakage problem. The issue is its cause. There is some common ground in Poon and Choi's evidence and even where there is none, their evidence do not necessarily conflict. Subject to the matters which I shall discuss below, I find both Poon and Choi generally honest and the differences in their evidence are largely due to the lapse of time and the different perceptions of being an occupant who suffered from water leakage and being the one who was accused of causing it.

Expert evidence and assessment

(1) Expertise of Wong and Lee

28. Wong styled himself as damage surveyor, engineer, loss adjuster, claim assessor, investigator and appraiser and gave his qualifications and experience as follows :

(a) associate member (Wong's 1st Report) or member (Wong's 2nd and 3rd Reports) or founding member since 1999 (Wong's viva voce evidence) of Chief Engineers Association (Construction and Maintenance);

(b) C member (Wong's 1st Report) or association member (Wong's 2nd Report) or member (Wong's 3rd Report) of American Society of Appraisers, a United States association dealing with assessment of damages and appraising value of properties, which he joined 5 years ago;

(c) member of the Institute of Professional Investigators (UK), which membership was recognised as indication of investigatory professionalism (mostly in relation to settlement of claims) within the United Kingdom, European Economic Community and other overseas countries (including Hong Kong);

(d) member of Hong Kong Concrete Repair Association;

(e) registered professional investigator (UK);

(f) competent person certified under section 14(2) of the Factories and Industrial Undertakings (Confined Spaces) Regulations, Cap.59 (about 2 years ago);

(g) certificate in professional management training for plumbing engineering (about 7-8 years ago) by The Institute of Plumbing Hong Kong Council, which became independent from its United Kingdom counterpart after 1997;

(h) certificate in concrete repairs by the Construction Industry Training Association ("CITA") (about 3 years ago); and

(i) certificate in concrete waterproofing and leakage repairs by CITA (about 3-4 years ago).

29. Wong said he had carried out investigating, surveying, and assessing loss in respect of water leakage and damage to premises for more than 1,500 to 2,000 water leakage claims over 18-20 years. He has also acted and been accepted as expert witness in court hearings in the Small Claims Tribunal, Lands Tribunal, District Court and High Court. Before Wong formed Proficient in 1994, he worked at an insurance company and as part-time surveyor with Kingsley Sit & Associates (from 1979) dealing mainly in claims settlement. He said about 60% of his portfolio of work related to water leakage claims. Proficient's business also related mainly to water leakage claims and resultant damage to property.

30. Although Wong styled himself as a surveyor, he is not registered with the Surveyors Registration Board under the Surveyors Registration Ordinance Cap.141 and is not a member of the Hong Kong Institute of Surveyors ("HKIS") established by The Hong Kong Institute of Surveyors Ordinance Cap.1148. He admitted that he did not know much about the Surveyors Registration Ordinance. Wong also agreed that members of Chief Engineers Association are not registered engineers but have overseas recognition (but he did not say what that was).

31. Lee had never heard of the Institute of Professional Investigators (UK). He understood Hong Kong Concrete Repair Association to be merely a trade union. Further, CITA's courses were short-term 20-30 hour courses with no entry requirements or examinations, and were targeted at construction industry workers. CITA only gave out attendance certificates.

32. Lee's academic qualification is BSc (Estate Management) and MSc (Project Management). He is a member of the Royal Institute of Chartered Surveyors (MRICS) and a registered professional surveyor (building surveyor) with the Surveyors Registration Board and a fellow member of HKIS, which is a world-recognised institution on par with the Royal Institute of Surveyors (UK) and the Australian Institute of Surveyors. Lee is also an authorised person under the Buildings Ordinance Cap. 123.

33. Lee has worked in the building and construction industry for 20 years and has inspected 300-400 buildings for defects. He has given evidence in court as expert on these matters on many occasions. BD has retained Lee Mark to investigate water leakage defects in buildings. Lee Mark has also carried out renovation works for various estates, including 2,000 units in Tsuen Wan Centre (many with water leakage problems) and 1,000 odd units in Pokfulam (many with external wall problems).

34. Although Ms Wong, counsel for D, did not challenge the expert capacity of Wong, I agree with her that Wong's qualifications and experience are relevant in assessing the weight of his evidence. There is no evidence that Wong gained practical experience upon completion of the courses he took, which appeared to be technician courses. The various institutions of which he is a member have no statutory recognition in Hong Kong and their membership requirements are unknown. It is unknown whether American Society of Appraisers is concerned with expertise in investigating causes of water leakage in contra-distinction to damage appraisal and other forms of damage to property. More significantly, Wong is not a registered engineer although he is said to be a member of Chief Engineers Association. The identity of the registration body in respect of his qualification as registered professional investigator in the United Kingdom is unknown. It appears from the evidence that Wong's experience was gained mainly in relation to claims settlement, property damage appraisal and loss adjustment. I have reservations as to his ability to speak reliably on expert investigation into the causes of water leakage. Such concern is reflected in some contradictory and speculative aspects of his evidence seen below.

35. On the other hand, Lee's qualifications are duly recognised by local statute, and his qualifications and experience are directly pertinent to building survey. I accept his expert status on speaking to the matters that are in issue.

(2) Wong's opinion as to the causes of the water leakage

36. Wong gave various causes for the water leakage problem :

(a) Floor Drain and the floor drain of the shower cubicle of 5/F Toilet leaked water through the dilapidated concrete Floor Slab;

(b) the dilapidated Floor Slab was not sufficiently water proof;

(c) the impact/force/vibration during Tiling Renovation impaired the water proof membrane and/or damp proof course of Floor Slab and the newly finished floor screed of Floor Slab was pervious ((a) to (c) above collectively called "Floor Slab Cause"); and

(d) Cistern and associated pipe fitting of 5/F Toilet leaked, so fresh and flush water mixed to become salty water to penetrate through Floor Slab ("Cistern Cause").

37. Wong also said FWS Pipes concealed in the walls might also be a potential cause and should be subject to WPT ("FWS Cause"). He opined that all of the above causes contributed cumulatively to the water leakage although he regarded Floor Slab Cause as the major cause and FWS Cause only had minimal effect.

(3) Observations by the experts from inspections

(a) Wong's observations of 4/F Unit

38. At Wong's inspection on 28th December 2000 (part of "Wong's 1st Inspection"), there were conspicuous watermarks on 4/F Ceiling and underside of 4/F Beam above the bathtub with severe plaster loosening and paint peeling. 4/F Ceiling showed a light film of orange colour (as stated in Wong's 1st Report but referred to as pink colour in Wong's 2nd and 3rd Reports) in the plaster near to the window and some brownish and dark spots due to rusting of reinforcement and mould growth as a result of the water leakage.

39. At Wong's inspection on 26th and 27th December 2001 and 9th February 2002 (part of "Wong's 2nd Inspection"), there were more plaster blistering and paint peeling, and damp marks extended to the entire 4/F Ceiling. Mould growth had developed and a section of concrete 4/F Ceiling had spalled due to water leakage affection. Soaking of reinforcement caused rusting which stained the plaster of 4/F Ceiling (mainly at 4/F Beam). There was relatively heavier damp and intermittent slow water dripping at 4/F Ceiling and Beam directly below Cistern. The 2 bottles of water collected by Poon (about 2 litres) appeared to contain clear water. Although Poon was unable to tell Wong the time taken for such collection, Wong guessed it was 2-3 weeks and water would drip for one day and not for the following 3 days. Wong found traceable pink coloured plaster at 4/F Ceiling, which had deepened in colour, but not yellow stains. Although he referred variously to pink or orange colour or both colours, he said it was more or less the same (probably more pink than orange).

40. At Master Bedroom, there was some plaster peeling at the beam soffit with grey (not pink) watermarks and a crack extending from the beam soffit to the floor due to water leakage affection. He had not asked Poon for how long the crack had appeared.

41. At Wong's inspection on 22nd September 2003 (part of "Wong's 3rd Inspection"), there was more conspicuous pink colour at 4/F Ceiling and Beam (with deepening of colour and expansion of the stains), and more brown spots (due to rusting of reinforcement) and stripping of plaster at 4/F Beam. There was no dripping water and the dampness had slowed down in that the moisture was less than as found at Wong's 2nd Inspection on hand feel checking. But 4/F Ceiling was still wet. There was a crack in the wall tiles of 4/F Toilet from the beam soffit downwards (not mentioned in Wong's 1st Report as it was small then) but Poon was unable to say when the crack was first noticed. In Master Bedroom, some watermarks were seen at the ceiling beam and beam soffit, and the crack had become larger but there was some improvement in the quantity of water seepage.

(b) Wong's observations of 5/F Unit

42. At Wong's 1st Inspection (part) on 28th December 2000, an old couple allowed him access to 5/F Toilet for 10 minutes but refused to let him take photographs. He discovered 5/F Toilet Renovation. 5/F Ceiling was dry by touch. Wong visually checked 5/F Unit water meter but was unable to say if FWS Pipes were leaking or not.

43. At Wong's 2nd Inspection (part) on 26th and 27th December 2001, FWS Pipes supplying water to the shower faucet as concealed in the concrete wall of the shower cubicle were directly above the heavy damp and dripping water at 4/F Ceiling and Beam. Water stains were noted on the wall tiles extending down from the elbow bracket of FWS Pipes of the shower cubicle ("Elbow Bracket"). As stated in Wong's 3rd Report, there was no sealant patched to the seams between Floor Slab and the walls/sanitary fitments. Photographs taken at Wong's 2nd Inspection showed that the dark grey Flushing Valve was rust-stained or stained with salty water indicating leakage from Cistern onto Flushing Valve or leakage of Flushing Valve itself.

44. At Wong's 3rd Inspection (part) on 22nd September 2003, other than some rough patches, the ceiling of 5/F Unit ("5/F Ceiling") appeared to be in good condition. Wong found clean and new sealant material patched to the seams between Floor Slab and the walls/sanitary fitments, which were done 2-3 days before Wong's 3rd Inspection. Further, he noticed some drip marks at the screw bracket at the base of Cistern ("Screw Bracket") suggestive of water seepage in the past. Rough sealant and white cement patching (with some gaps) had been applied to the base of Cistern. The Flushing Valve had been replaced by a white valve. Close inspection of Floor Drain and the base of Cistern showed relic of pink dye. There were 2 cracks in the ceramic wall tiles covering 5/F Beam (directly above the gas heater, which would bring an increase in temperature when in use, thus causing cracking).

45. The lower part of the walls and skirting of Master Bedroom and the corridor adjacent to 5/F Toilet showed heavy watermarks indicating water seepage from 5/F Toilet. Sealant has been applied as a temporary repair job to seal the seam between the floor and the walls. Water seepage also resulted in water stains and blackened floor tiles of the teak parquet flooring.

(c) Lee's observations of 4/F Unit

46. Lee was only allowed to inspect 4/F Toilet and Master Bedroom on 27th December 2001 and 22nd February 2002 (part of "Lee's 1st Inspection"). He found moisture when he touched 4/F Ceiling and Beam by hand and water stains along 4/F Beam. Lee did not notice any dripping water but accepted there might be slow dripping other than at the time of his inspection. Mould growth, yellow stain and blistering paint were visible on 4/F Ceiling. The orange and light brown colours at 4/F Ceiling were spalled concrete. Water stains were also observed along the edge of the ceiling soffit at Master Bedroom.

47. No water leakage or dampness was noted at Lee's inspection on 22nd Sepetmber 2003 (part of "Lee's 3rd Inspection"). The condition of 4/F Ceiling and the ceiling of Master Bedroom was about the same but the ceilings were dry. At 4/F Ceiling, there were rust stains along cracks and spalling concrete. Lee disagreed that the pink colour at 4/F Ceiling had deepened and said such suggestion was probably due to how photographic negatives were developed. Indeed, some later photographs showed a lighter colour.

(d) Lee's observations of 5/F Unit

48. At Lee's 1st Inspection (part) on 24th and 27th December 2001, he found 5/F Toilet and the sanitary fitments in good condition, which condition was maintained up to Lee's inspection on 17th May 2003 ("Lee's 2nd Inspection") and Lee's 3rd Inspection (part) on 22nd September 2003. Choi said no patch works were done at 5/F Toilet and Lee confirmed this by his observation at Lee's 3rd Inspection. In fact, there were some dirt marks on the sealant at the seam of Floor Slab of shower cubicle and the wall. Wong's impression of the sealant being new was due to different distances and angles adopted for photographs taken during Wong's 2nd and 3rd Inspections. Lee agreed some water stains were found at Elbow Bracket but denied that Flushing Valve was replaced. The shape of the valve was still the same although cleaning might have given Wong the impression that it had been replaced. The screw nut inside Screw Bracket would have rusted on contact with air moisture over the years, so there would be some rust stains.

(e) Observations of the external wall

49. HB Centre was over 20 years old. Block F was a 15/16-storey reinforced concrete construction with an outer wall ("Outer Wall") on each floor outside the external wall of the toilet of Unit No.2, so that it was partially exposed to the elements.

50. At Wong's 1st Inspection (ie before Building Renovation), he observed from the ground floor that the Outer Wall was in good condition. As reported in Wong's 3rd Report, he also found the partially exposed external wall of 4/F Toilet in good condition with no live watermarks or obvious cracks.

51. At Lee's 1st Inspection, Lee inspected the external wall of 5/F and 4/F Toilets and found no apparent defects. As Poon told him water leakage occurred even on a sunny day, he discounted rainwater seepage as a cause of the water leakage at that stage. However, Lee was unable to check the external wall of other units. By the time of Lee's 3rd Inspection, EW Renovation had been completed and the external wall re-painted. Although he did not oversee EW Renovation, Lee knew patch repairs of identified problem areas of the external wall, tile filling and re-painting were done to repair the spalled concrete and plaster and to tackle the external wall water seepage problem. Such patch repairs might not address all defects in the external wall and if some problem areas were omitted in the repairs, they would be attacked by rainwater.

(4) Floor Slab Cause

(a) Concrete moisture meter ("Meter")

52. Wong said he relied on equipment testing to conclude that 5/F Unit caused the water leakage at 4/F Unit and it was more scientific than the hand feel method adopted by Lee. Wong probed 4/F Ceiling and Beam with Meter which gave a reading of 100% relative humidity ("RH") at all 3 inspections. The reading of 80% RH from the wall adjacent to 4/F Toilet at Wong's 2nd Inspection was on the high side. When compared with the reading of 20-30% RH for the walls of the living room of 4/F Unit and the wall outside 4/F Toilet at Wong's 1st Inspection and the reading of 60-70% RH at 5/F Ceiling at Wong's 2nd and 3rd Inspections, and given that water flows from a high to low level, Wong opined that the readings proved "a slow water flow entering and appearing at the ceiling of [4/F Unit]" from 5/F Unit but there was no water seeping into 5/F unit from the floor above.

53. Wong opined that the moisture content of concrete (open to air) must correspond with water vapour saturation in the air. Since air cannot have 100% moisture (70% RH being the normal reading), 100% RH reading for 4/F Ceiling indicated water seepage. When cross-examined as to how RH (ie moisture content of air) can relate to moisture content in concrete/plaster, Wong said Meter's technological design could detect moisture in concrete up to one inch in depth. Wong, at the request of Ms Wong, produced Meter's brochure leaflet ("Meter Leaflet") (same model as used by Wong) which stated inter alia that Meter "will give you an instant reading of moisture content up to 6% concrete ...... enabling you to make an informed decision on when to install the floor covering". Wong explained that if 6% volume of water was added to concrete, it would give 100% RH reading.

54. Meter Leaflet also made no mention of Meter's ability to test moisture up to one inch in depth, but Wong said as expert he knew Meter's capability. Meter Leaflet stated Meter was for use by the flooring industry and did not say it was designed for testing water leakage. Wong explained that in the United States (Meter was manufactured by an American company), houses were made of timber but the flooring was made of concrete, so Meter could be used to test moisture content in concrete.

55. Meter Leaflet also stated that Meter "will not give true readings through paint or floor covering", and that Meter's "electrodes must be in direct contact with concrete surface", which "must be smooth and free from dust". Wong accepted that Meter could not be used on plastic covering and was not very effective on wall tiles, but claimed Meter Leaflet only meant that the readings would not be so accurate, not that it would fail to give true readings. He as expert would know the moisture content despite slight inaccuracies. Further, only emulsion (water soluble) and not polymer or synthetic paint was used at 4/F and 5/F Toilets, so Meter could still give reliable readings. Although Meter Leaflet did not distinguish different types of paint, Wong said his interpretation was practical since Meter Leaflet could not be expected to cover everything. Further, he used Meter to test against parts of 4/F Ceiling where the paint had peeled off.

56. Lee rejected Wong's suggestion that Meter used RH as the measuring range. He explained that as moisture saturation level of air varies with changes in temperature, RH reflected moisture content of air (and not moisture content within materials such as concrete) at a designated temperature. For measuring moisture content of concrete, the normal moisture content is 2-3% whilst total moisture saturation is 6% (see Meter Leaflet's measuring range of up to 6% concrete). As shown on Meter Leaflet, Meter has 2 types of readings, the first one from 1-6 (since moisture saturation of concrete is 6%) and the second one from 1-100 (which converts the aforementioned range into percentage based presentation).

57. Lee said that according to Meter Leaflet, "regular checking of moisture content during the drying out period of a new concrete floor or floor screed is important to ensure it has reached sufficient dryness to accept the floor covering" (ie Meter's purpose). Thus Meter's purpose of usage is to check whether a new concrete floor has properly dried out for otherwise the adhesive will not set the flooring securely. Lee said it was inappropriate for Wong to use Meter at 4/F and 5/F Units as he did. There is nothing in Meter Leaflet to suggest that Meter could read moisture content up to one inch of concrete. In any event, as the 6-inch Floor Slab had an inch of plaster, even this claimed capability cannot assist.

58. Lee said Meter Leaflet clearly stated that Meter should not be used on wall/ceiling with emulsion or any other paint. Although some paint had peeled off at 4/F Ceiling, paint was applied in layers so there might still be paint or residue of paint even if some paint at 4/F Ceiling peeled off.

59. Having carefully considered Wong's and Lee's evidence and Meter Leaflet, on balance I find that I cannot safely rely on Wong's opinion and conclusions based on Meter's readings. First, I accept Lee's opinion that, taking Wong's contentions in relation to Meter to their highest, Meter's readings were only capable of showing whether dampness existed at certain locations or not but could not tell that 5/F Toilet caused the water leakage. I also accept Lee's explanation (which conformed with Meter Leaflet) that Meter's measuring range was based on a maximum of 6% concrete. Meter Leaflet did not mention RH at all. I accept Lee's opinion that RH measured moisture content in air at designated temperature and not moisture content in concrete.

60. Secondly, I am with Lee when he said hand feel examination by an expert plays an effective and reliable role. Even Wong admitted that Meter is unable to read moisture content beyond 100% RH, so different degrees of dampness can only be distinguished by visual observation and hand touch, ie the methods adopted by Lee.

61. Thirdly, Wong's use of Meter was not in line with the purpose stated in Meter Leaflet. Meter Leaflet did not mention that Meter could measure moisture content up to a depth of one inch of concrete. The whole tenor of Meter Leaflet was for Meter to test the dryness of the concrete surface (instead of the inner contents of concrete) before accepting floor covering. Meter Leaflet said the electrodes should be in direct contact with the concrete surface. The electrodes do not probe the inner contents of the concrete.

62. Fourthly, Meter Leaflet requires the surface to be paint-free, smooth and free from dust, hence the targeted test material is "new" concrete floor or floor screed. Given that there was paint at 5/F Toilet and other rooms of 4/F Unit, and given the condition of 4/F Ceiling with blistering paint, peeling plaster, rust stains and mould growth, the reliability of Meter's readings is doubtful. I find there is no basis from Meter Leaflet or otherwise for Wong to distinguish between emulsion and other paints.

63. I therefore find on the balance of probabilities that Meter was unhelpful in determining whether water leakage originated from 5/F Unit. Indeed, I find Wong's approach to the use of Meter and the conclusions he drew from the readings unscientific.

(b) 1st CWT and orange/pink coloured plaster

64. Wong took some orange/pink coloured plaster samples at 4/F Ceiling during Wong's 1st Inspection for testing by Hong Kong Standards and Testing Centre ("HKSTC"), which found "a very light orange artificial colouring matter ...... detected by [thin layer chromatography] method". HKSTC could not correlate the artificial colouring matter to FEHD Dyes as only FEHD knew what FEHD Dyes were. However, Wong concluded that, since only FEHD carried out CWT prior to HKSTC's testing, the orange matter was from FEHD Dyes which passed through Floor Slab to appear at 4/F Ceiling.

65. Wong reasonably speculated that the orange matter was from Orange II because its name contained the word "orange". Although he did not know the colour of the remaining FEHD Dyes, he believed that Eosin yellowish should be yellow and one of the other FEHD Dyes might be pink because he knew (and observed) FEHD often used pink dye. Wong was not trained in chemistry and he accepted the names of FEHD Dyes might be trade names. He did not know which coloured FEHD Dye was poured onto which Test Area during 1st CWT.

66. Wong said that due to the short lapse of about a month between 1st CWT and FEHD's collection of plaster sample, GI's non-positive result did not negate a finding that the water leakage came from 5/F Unit. HKSTC found colour matter in plaster sample from 4/F Ceiling some 20 months after 1st CWT. Wong opined that colour dye would take 2-12 months to pass through small gaps between ceramic tiles and Floor Slab (8 inches thick) and appear at 4/F Ceiling. Since Concrete is a high-density substance of aggregate composition of cement and sand with tiny voids, most dye particles would be absorbed by the concrete and it would take a long time for the dye particles to percolate through to 4/F Ceiling. In time, the amount of dye particles at Floor Slab would decrease but they would increase at 4/F Ceiling, as reflected in the expansion and deepening of pink colour at 4/F Ceiling at Wong's 3rd Inspection.

67. Wong gave various explanations for his change of description of plaster colour from orange to pink. First, there were in fact both pink and orange dyes. Secondly, he said the dye mixed with rust to turn light brown or orange. Thirdly, the orange dye transformed into pink colour upon mixing with rust. Then Wong said in fact colour was not important and it was the artificial colour matter that mattered since it necessarily came from FEHD Dyes. However, he accepted that one of CWT's prime purposes is to observe whether any dye colour appears at the ceiling of the flat below and therefore colour is a relevant matter.

68. Wong accepted that if FEHD were prepared to re-test plaster samples and there was sufficient dye content, they would be able to verify whether the artificial colour matter was from FEHD Dyes. But he opined that when D made the re-testing suggestion just after Wong's 1st Report, it was at an early stage so there might not be enough dye content, which would produce a false negative result, particularly if GI adopted the same standard for analysis. But under cross-examination, Wong agreed that by Wong's 1st Report more than 12 months have elapsed after 1st CWT, so FEHD Dyes would have diffused sufficiently for testing. Wong was therefore constrained to say that FEHD might refuse to re-test plaster samples.

69. On the other hand, Wong said dye mixed with other materials (eg dirt or liquid soap) in concrete would transform into another colour and composition (due to chemical reaction, the nature of which Wong did not know), hence it was doubtful whether further re-testing by FEHD would be useful. As the dye in its original form decreased in quantity over time as a result of such transformation, the orange colour would transform into pink and deepen over time.

70. Despite Wong's reliance on the correlation between 1st CWT and HKSTC's test results, he was critical of 1st CWT. From his observations of FEHD carrying out CWT on other occasions, he said FEHD did not keep the liquid dye at the test areas for a sufficiently long time for proper diffusion and did not allow sufficient time to lapse after CWT before taking plaster sample for analysis.

71. At Wong's 3rd Inspection, he also took a close look at Floor Drain and the base of Cistern and found relic of pink dye set by FEHD. As the pink colour corresponded with the pink coloured plaster at 4/F Ceiling and Beam, this was strong proof that the water leakage originated from 5/F Toilet. Wong later accepted in his evidence that the relic might also be from the brown dye used by Lee at 2nd CWT.

72. Lee was unable to conclude that the yellow stains found at 4/F Ceiling at Lee's 1st Inspection were from 1st CWT. Although common sense suggested that Orange II and Eosin yellowish should be orange and yellow in colour, he could not as a professional say Orange II must be orange in colour because the word "orange" is in its name. The names of FEHD Dyes may also be trade names. Further, Lee did not know which coloured dye was poured onto which Test Area during 1st CWT. Although Wong used orange and pink interchangeably, Lee said they were not the same. Orange is an original colour but pink is a mixture of red and white. Wong's observations were not consistent.

73. Lee considered it unlikely that colour dye would take more than a month to seep through Floor Slab of 6 inches' depth if there was water leakage. Concrete is made by sand and small stones held together by cement sand mix which had some water resistant ability. But the density of concrete (which depended on the how much cement was used and not on the presence/absence of reinforcement) had nothing to do with the speed of diffusion. Since concrete was mixed at the construction site during building erection and not in a laboratory environment, it was inevitable that the concrete would have some cracks, hence the need for water proof membrane. If there were water leakage, water would find its own path through the cracks and weak points in the concrete and the colour dye would not take 2-12 months to seep through.

74. Lee did not know where the light orange artificial colouring matter in HKSTC's test results came from. But Wong's emphasis on the presence of artificial matter was difficult to understand for paint (including colour and particles) itself was artificial. Although the paint on 4/F Ceiling appeared visually to be white in colour, the paint might contain other (even orange) colouring.

75. Lee disagreed that colour dye would mix with other substances to transform into another composition or colour, so that the original dye would decrease in quantity. Wong's such assertion is contradictory to his own view that it would take 2-12 months for the colour dye to diffuse through to the ceiling below for proper testing. If testing should only be done 2-12 months after CWT but there would be less original dye as time passed, it would mean that proper laboratory analysis would be impossible.

76. Lee concluded that both 1st and 2nd CWT showed that the water leakage was not from 5/F Unit (although FEHD was unable to ascertain the cause of the water seepage).

77. Having considered the evidence and submissions, I reject on the balance of probabilities Wong's suggestion that the orange/pink colour found at 4/F Ceiling was from FEHD Dyes. Wong's evidence in this respect is speculative and unreliable :

(a) It is unscientific for Wong as expert to say that just because the name of a dye (and accepting it may only be a trade name) contains the word "orange" or "yellow" it necessarily means that the dye is orange or yellow in colour. No attempt has been made to seek clarification from FEHD as to the colour of FEHD Dyes. To go further to say one of FEHD Dyes must be pink in colour because FEHD often uses pink dye is speculative. Wong's claim of the presence of relic of pink dye at 5/F Toilet over 4 years after 1st CWT on the assumption that one of FEHD Dyes was pink is speculative. Wong's criticism of FEHD's methodology for 1st CWT is also speculative for there is simply no evidence as to how 1st CWT was done.

(b) The imprecision of the colour observed (pink/orange) has not been satisfactorily explained. Wong's explanations are a moving feast, from there being orange and pink dyes, to mixing with rust to become orange colour and to transformation from orange to pink colour. None of these explanations can be found in Wong's 1st, 2nd and 3rd Reports. Clearly Wong changed tack as it suited him in the course of giving evidence. I find his explanations unreliable.

(c) Wong's opinion relating to how the orange and/or pink dyes passed through Floor Slab to 4/F Ceiling is difficult to understand. Choi confirmed that different coloured dye water was poured into each of the Test Areas. Even if FEHD Dyes had orange and/or pink colour amongst them, there is no evidence as to which coloured dye was poured to which Test Area. If orange/pink dye water were poured into the water closet and/or washbasin, their relationship to Floor Slab have not been explained.

(d) I reject the contention that it would take 2-12 months for the dye to seep through to 4/F Ceiling. First, Wong gave the density of concrete and the absorption of dye particles by the concrete as the reason for allowing sufficient time lapse after CWT before testing the plaster. However, on P's case, FEHD used liquid and not powder-dissolved dye and Wong has not explained the relevance of absorption of dye "particles" by concrete in relation to liquid dye. Further, since it is Wong's case that water percolated continuously through Floor Slab to 4/F Ceiling, it is difficult to understand why liquid dye would take such a lengthy period to get through bearing in mind that Floor Slab was 6-8 inches in depth only. I also accept Lee's explanation that water seepage occurred because water followed its own water path through weak points and cracks in the concrete and is not affected by the density of concrete. I accept Lee's evidence that colour dye (whether liquid or powder-dissolved dye) will not require more than a month to seep through to 4/F Ceiling if there were water leakage from 5/F Toilet.

(e) It is clear that Wong relied on HKSTC's test results (which did not by itself correlate to FEHD Dyes) to reject possible negative result on any re-testing as a false negative. Such blinkered approach led to illogical contradictions. First, Wong said HKSTC's test results indicated that the dye was pushed down to 4/F Ceiling over time thus causing expansion of orange/pink coloured plaster and hence orange artificial colouring matter was found by HKSTC. On the other hand, he said that even if FEHD (who knew what FEHD Dyes were) re-tested the plaster after HKSTC did its test, the dye would transform into another colour and substance over time so there would be too little dye content in the plaster for a positive result. Secondly, Wong accepted that a proper CWT could confirm whether the outlet drains and Floor Slab were water proof and intact. But at the same time, his evidence suggested that CWT would be practically useless if corresponding dye colour could not be reliably observed or tested from 4/F Ceiling at an early stage (because the dye took time to percolate down) or as time passed (because of transformation of the dye).

(f) I accept Lee's evidence that the purpose of CWT is to observe whether colour dye appears at the ceiling of the floor below the test premises. The presence of the relevant dye colour at the ceiling below will be indicative of water seepage from the relevant test area. There is no suggestion that FEHD observed any colour of FEHD Dyes at 4/F Ceiling on 11th May 1999. I reject Wong's suggestion of reliance on the presence of artificial colouring matter instead of colour. This shift in Wong's evidence is not in his reports and quite clearly came as a result of vigorous cross-examination on his observations of orange/pink colour plaster. I accept Lee's contention that paint is an artificial matter, so Wong's plaster samples (scrapings from surface of 4/F Ceiling and not bore samples) do not hold the distinction of being the sole artificial colouring matter.

78. I therefore find HKSTC's results unhelpful in determining whether the water leakage came from 5/F Unit. I also find that there is insufficient evidence on the balance of probabilities to correlate the claimed orange/pink colour plaster with FEHD Dyes.

(c) 2nd CWT

79. Lee carried out 2nd CWT in Wong's presence by pouring blue, green, dark purple (not brown) and red colour dye water into/on Test Areas. Wong said the dye poured onto Floor Slab near to Floor Drain was brown although he eventually accepted the photographs showed deep purple colour. Lee did not observe any of such colours during re-inspection of 4/F Ceiling.

80. Wong accepted that a proper CWT would prove whether the drainage water pipes or Floor Slab were water-proof and intact. He did not carry out any CWT but criticised 2nd CWT's reliability. First, Lee used powder and not liquid dye (as used by FEHD). The powder particles were too coarse to dissolve fully in water, so most of the residue would drain away through Floor Drain and CWT would not produce a true result. Wong did not raise this objection during 2nd CWT.

81. Secondly, Wong said the dye water was left at Test Areas for too little time before it drained away, so 2nd CWT could only test the outlet drains and not Floor Slab. Dye water should be left to stand at Test Areas for 24 hours. Thirdly, re-inspection of 4/F Ceiling on 22nd February 2002 (less than 2 months after 2nd CWT) had not allowed sufficient time for proper diffusion. Fourthly, concrete samples should be taken for laboratory analysis for Lee could only visually observe the plaster surface and not the concrete of 4/F Ceiling.

82. Lee said both powder and liquid dye could be used for CWT without affecting the reliability of the test results. Powder dye purchased from hardware shop (whose chemical or trade name Lee did not know) was traditionally and commonly used and once dissolved, it was the same as liquid dye. Lee denied that powder dye was too coarse-grained for CWT. Liquid dye was useful where there was no water available at the test area. For 2nd CWT, Lee used powder dye as a substantial volume of dye water was needed to cover Floor Slab.

83. Lee explained that 2nd CWT was like pouring water (albeit coloured water) onto Test Areas. Floor Slab was about 6 inches in depth, so if there were water leakage, the colour dye should be visible at 4/F Ceiling in a few hours' or 1-2 days' time, not 2-12 months as alleged by Wong. In fact, Lee had deferred re-inspection of 4/F Ceiling to 22nd February 2002 at the request of D's solicitors in light of Wong's allegations.

84. Lee said that the purpose of CWT was to observe whether colour dye was visible at the ceiling below. If so, common sense would indicate the source of the water leakage without the need to have laboratory testing of the chemical compound of the plaster. Given Lee's experience, he was well equipped to carry out visual observation for dye colours at 4/F Ceiling.

85. I find on the balance of probabilities that 2nd CWT is a proper CWT and can be relied on to determine whether Floor Slab or outlet drainage system of 5/F Toilet is a possible cause of the water leakage :

(a) A key purpose of Wong's 2nd Inspection was to observe Lee's 2nd CWT. Yet he did not even observe or record the deep purple colour of the test dye (which I accept) correctly. His observations are suspect. Further, Wong cannot satisfactorily explain why no objection was raised during 2nd CWT and why knowing that (i) 2nd CWT was defective, (ii) a proper CWT will prove whether Floor Slab and outlet drains of 5/F Toilet were leaking, and (iii) his brief was to ascertain the origin of the water leakage, he did not recommend carrying out CWT at all in the intervening 20 months to trial.

(b) I accept Lee's expert evidence that powder-dissolved and liquid dyes produce equally reliable results and powder-dissolved dye is commonly and effectively used. I do not accept Wong's opinion that powder dye is too coarse-grained. Even if some residue was drained away, and assuming reliance on Wong's theory of particles being pushed downwards through Floor Slab by reason of continuous water seepage, no explanation is given as to why none of 2nd CWT's test dye colours appeared at all at 4/F Ceiling in 19 months to Lee and Wong's 3rd Inspection.

(c) I also reject Wong's contention that the dye water should be left standing for 24 hours and he did not explain why 24 hours is appropriate. Further, if CWT is to emulate ordinary usage of the toilet to see if water seepage occurs, one doubts whether leaving water standing on Test Areas for 24 hours reflects ordinary usage. As pointed out by Lee, a toilet is not intended to be a water tank.

(d) I have rejected Wong's opinion that 2-12 months are required for colour dye to percolate through to 4/F Ceiling.

(e) I accept that one of the prime functions of CWT was to see if test dye colours appear at the ceiling below and that Lee has the expertise to make such visual observation. Even Wong did not say the colour of any test dye of 2nd CWT was seen at 4/F Ceiling even up to Wong's 3rd Inspection. Although GI and HKSTC carried out laboratory analysis of plaster sample, I do not find such chemical analysis necessary where no colour is observed. Even if there is water seepage, water follows its own path and will not necessarily appear directly beneath the point of leakage or test area. Further the Test Areas cover almost the whole of Floor Slab and all outlet drains. If no colour of any of the test dyes is observed, a difficult question arises as to from which part of 4/F Ceiling one should take the plaster sample for chemical analysis. Even if a plaster sample is randomly taken from 4/F Ceiling, the result is not necessarily indicative.

I therefore do not accept Wong's criticisms of 2nd CWT.

(d) Chloride testing

86. At Wong's 2nd and 3rd Inspections, he found chloride had seeped out to become powder or crystals at 4/F Beam and beam soffit of 4/F Toilet. Wong scraped some of the white crystals from the beam soffit and moistened them with a drop of water, which he then placed on the glass of a hand refractrometer ("Refractrometer"). A liquid sample is required as Refractrometer only checks chloride content in liquid. The readings exceeded 10% indicating a high concentration of chloride, which proved that salty flush water mixed with fresh water to flow through tile joints or weak points from 5/F Toilet to 4/F Ceiling. Lee did not carry out any chloride test with equipment. Since no chloride crystals were found at 5/F Toilet, the flush water must come from 5/F Toilet and not from any other floor above.

87. Wong went further to say that chloride testing showed flush water leaked from Cistern onto Floor Slab and diffused to 4/F Toilet. Although chloride testing was done at Wong's 2nd Inspection, Wong only viewed the outside of Cistern, so he came to the above conclusions before inspecting Cistern. Wong went on to say Cistern had leaked or flush water overflowed intermittently from the water tank for a long time (as evidenced by the accumulation of chloride crystals at 4/F Ceiling), which he regarded as reasonable assumptions, so there was no need to inspect Cistern.

88. At Wong's 2nd Inspection, he did not carry out chloride testing on the dripping water from 4/F Ceiling because flush water would mix with fresh water to dilute the chloride content, hence Refractrometer might not be able to check the presence of chloride. But when pressed, Wong said he did test the dripping water, which was fresh water, but he forgot the test result which he did not record as it was unimportant. As the occupants of 5/F Unit used a large volume of water daily, there was a run of clear water. Wong opined that the wetness at the centre of 4/F Ceiling (clear water from shower cubicle at 5/F Toilet and Floor Drain) and Beam (seepage from Cistern) was from different sources.

89. Wong said that laboratory testing of concrete sample was not required to check chloride content in concrete as Refractrometer could provide reliable results. He knew Building (Construction) Regulations Cap.123 specified chloride content of concrete mix (but he did not know whether concrete contained calcium chloride), but as he discovered a high concentrate of chloride by Refractrometer, it must have exceeded the statutory limit. Wong referred variously to discovery of chloride (general term) or sodium chloride (edible salt), the chemical composition of which might be slightly different but immaterial as they both had the same character.

90. Lee was not present when Wong carried out chloride testing with Refractrometer. Chloride is a chemical and there are different types of chloride, such as calcium chloride and sodium chloride. Concrete itself has chloride iron as a result of the use of sea sand in making concrete or addition of quick-drying admixture, both of which contain chloride. Regulation 56 and Table 1 of Building (Construction) Regulations Cap.123 specified that chloride content of concrete should not exceed 0.35% as compared with cement. Where there is water leakage, finding chloride crystals (or lime) is a common phenomenon called effervescence because chloride iron in concrete dissolves and surfaces as whitish grey crystals. Lee had seen chloride stalactites at the floor below a roof at another site even when there was only rainwater (ie fresh water) seepage from the roof.

91. Lee said the proper method to test chloride content in concrete is to carry out laboratory testing of concrete sample by chloride content and aggregate cement ratio tests. Refractrometer only showed the consequence of chloride being found (which was undisputed) and not chloride content in concrete, and thus the findings were insufficient to conclude that the chloride content of Floor Slab exceeded the statutory limit or to identify the source of water leakage. Further, Wong's test method was not scientific because chloride concentration depended on the quantity of water used to dissolve the chloride crystals. If more water was used, the chloride content would be more diluted and vice versa.

92. Lee accepted that as flush water was salty water, it was normal to have some salty water vapour at 5/F Toilet. 5/F Toilet Renovation took place in 1996 and 5/F Toilet was necessarily used every day by the occupants. If there were any leakage from Cistern, the consequences would have been apparent at 4/F Ceiling in 3-4 months instead of in 2-3 years.

93. On the balance of probabilities, I do not find chloride testing by Refractrometer of assistance in determining the cause of the water leakage. Lee did not dispute that chloride crystals were found at 4/F Ceiling and that appears to be all Refractometer is able to prove. I am unable to accede to Wong's conclusion that this necessarily means that flush water leaked from Cistern via Floor Slab to 4/F Toilet. I cannot see how Wong can come to this conclusion without even attempting to check Cistern and the flushing system (see my analysis below). To say that Cistern leaked for a long time intermittently without inspecting or flushing it is nothing more than a speculative attempt to project a reason from the manifestation of lime. Wong also could not satisfactorily explain the effect of water seepage on normal statutorily prescribed chloride content in concrete. I accept Lee's opinion that chloride leaching from concrete is usual where there is water seepage (even fresh water leakage) resulting in effervescence, which is a possible explanation of the discovery of chloride crystals at 4/F Ceiling.

94. I also accept Lee's opinion that proper testing of chloride content in concrete is not by Refractrometer but by laboratory testing as he described. Further, Wong's differing answers as to the primary fact of whether he did or did not carry out chloride testing for the dripping water makes one skeptical of his evidence. If he did not carry out any chloride testing of the dripping water, it is also difficult to understand how he came to the conclusion of 2 different sources of water leakage for 4/F Ceiling. In any event, 2nd CWT (which I accept as proper CWT) refutes the allegation of defective Floor Slab.

(e) 5/F Toilet Renovation

95. Wong said concrete is high-density material with water resistant ability due to close adhesiveness of its particles. Damp proof course is a chemical mixed with cement and sand with water proof effect. But the water resistant ability will only hold out for a certain period, so it was necessary to apply water proof membrane (a polyester membrane painted on the floor to become a water proof layer) to the concrete floor. If the workmanship of the water proof membrane is poor, water will first seep through weak points/cracks in concrete and the affected area will expand after further wearing.

96. Wong said using pneumatic equipment to break open the original floor tiles might have caused cracks in Floor Slab or damage to damp proof course/water proof membrane. If a new water proof membrane was not applied, or its workmanship was poor, or proper materials were not used, or incorrect mixture was adopted for damp proof course/cement sand screed during 5/F Toilet Renovation, water would seep through the concrete and/or the new but impaired water proof membrane. Since concrete has some water resistant ability and the new water proof membrane (if any) would take time to weaken through wearing, it was not surprising for problems to only surface 2-3 years after 5/F Toilet Renovation in 1999. But Wong admitted that he did not know whether a good water-proofing job had been done for Floor Slab prior to laying the new ceramic tiles or not.

97. Since damage to Floor Slab as aforesaid could not be visually observed due to covering by floor tiles, Wong said the proper test was to carry out CWT for whole of Floor Slab. He did not do so but relied on testing by Meter and Refractrometer and by analysis of 1st CWT to prove that the water leakage was from 5/F Unit.

98. Lee said he did not know how 5/F Renovation was done but normally there was no need to use pneumatic equipment. The original ceramic tiles would be broken up by hammer. The original water proof membrane would have been removed during Tiling Renovation and a new water proof membrane applied. Lee agreed that if it was not applied or if its workmanship was poor, water leakage would occur, but this was refuted by 2nd CWT. Lee denied that there could be wearing of the water proof membrane over time. 5/F Toilet Renovation was not a structural alteration as it did not affect the frame of the building.

99. In my view, Wong's assertion that Floor Slab was impaired is premised on impact/force/vibration caused by the use of pneumatic equipment on Floor Slab during 5/F Toilet Renovation. I accept on balance of probabilities Choi's evidence that the original tiles were broken up by small hammer and this is supported by Lee's expert evidence. There is no primary evidence at all to support Wong's speculation that pneumatic equipment was used.

100. In any event, I accept that it is inevitable that the original water proof membrane was destroyed during 5/F Toilet Renovation. The issue is whether a new one was applied and whether it was well applied. There is simply no direct evidence from P (and Wong admitted that he did not know) to suggest that there was no new water proof membrane or that its workmanship was poor. 2nd CWT (which I have found to be proper and reliable) showed that Floor Slab was intact and water proof. If there were no new water proof membrane laid or the water proof membrane was impaired, I have strong misgivings over Wong's claim that it would take 2-3 years for water to leak through to 4/F Ceiling. Although concrete has water resistant ability, I accept Lee's evidence that water seeks the easiest path to follow (see below), so water would attack inevitable cracks in concrete (if there were no water proof membrane) or defective parts of the water proof membrane (if an impaired one was laid). Further, since the water proof membrane was laid inside Floor Slab, Wong was not able to explain why it would wear. Therefore, on balance, I reject Wong's opinion that water leaked through impaired Floor Slab due to defective 5/F Toilet Renovation.

(f) Usage of 5/F Toilet

101. Wong said there might be more than one seepage point at Floor Slab, eg at the shower cubicle or below the water tank of Cistern or near to Floor Drain between the shower cubicle and Cistern. How the occupants used 5/F Toilet affected the water leakage and water dripping. If water were spilled onto Floor Slab outside the shower cubicle during shower, water would seep through Floor Slab. Seepage might also occur at Floor Slab of the shower cubicle depending on how long water was retained or left standing there.

102. However, if Floor Slab were sufficiently water proof, usage of 5/F Toilet would not cause water seepage. Wong said patch repairs carried out by D by applying sealant to the seams of Floor Slab and walls/sanitary fitments of 5/F Toilet shortly before Wong's 3rd Inspection cured some but not all water seepage entry points on the dilapidated Floor Slab. Thus, the water leakage had not fully ceased by the time of Wong's 3rd Inspection. Wong said that when Poon said there was improvement and water no longer dripped for some months prior to trial, Poon only meant the water seepage was less serious, which Wong reasonably speculated was a natural consequence of the occupants of 5/F Unit pouring less water on Floor Slab and being more careful in taking showers to avoid spillage.

103. Lee said that voids in the concrete hold oxygen, carbon dioxide and moisture diffused from the air over a period of time, so some moisture in concrete is normal. If there is water leakage, water will follow cracks or find its own path, so water stains do not necessarily appear directly below the point of leakage. If there were no cracks, Floor Slab would not soak up water unless 5/F Toilet was a large water tank with a constant and large quantity of water. Few occupants of premises used toilets in the unusual ways contended for by Wong.

104. In my view, there is simply no evidence as to how the occupants used 5/F Toilet save and except Choi's evidence that usage was normal and did not alter at all since 5/F Toilet Renovation (which I accept). The number of occupants of 5/F Unit also remained constant. There is no basis for suggesting that the occupants of 5/F Unit poured water onto Floor Slab outside the shower cubicle or deliberately allowed water to stand in the shower cubicle for an excessively long time or substantial volume of water spilled from shower cubicle to Floor Slab outside the shower cubicle. Even if these practices actually occurred, 2nd CWT (which I accept as proper and reliable CWT) refutes the suggestion that Floor Slab was neither intact nor water proof. Wong seemed to suggest the improvement seen at Wong's 3rd Inspection was the result of change(s) in the usage of 5/F Toilet by the occupants of 5/F Unit, but there is no evidence when and how their practices altered to result in heavier dampness at Wong's 2nd Inspection and distinct improvement at Wong's 3rd Inspection. In my view, Wong's suggestion is speculative.

(g)Cracks and observations at rooms adjacent to 4/F Toilet

105. Wong said cracks and re-painting at various locations showed that there was water seepage although he claimed that the cracks at 5/F Beam were due to water vapour and heat from the gas heater and not water seepage :

(a) At Wong's 3rd Inspection, he saw an obvious crack at 4/F Toilet from the beam soffit downwards caused by erosion due to leakage of water containing chloride.

(b) There was a crack on the wall of Master Bedroom extending from beam soffit downwards.

(c) The new painting at the ceiling and beam of Guest Bedroom at Wong's 1st Inspection indicated that some temporary repair job had been done to cover the watermarks there.

106. Lee explained that the cracks found at 5/F Toilet were due to rusting of the reinforcement in 5/F Beam. Oxygen and carbon dioxide in the air would seep into the concrete and if the protective layer of the reinforcement for prevention of chemical reaction with carbon dioxide was impaired, the steel might absorb oxygen and carbon dioxide from the air and then rust. Once rusted, the reinforcement would expand and cause cracks. This caused cracks found at 4/F Unit, including the crack found at Master Bedroom and 4/F Toilet.

107. On balance I accept Lee's explanation. I find it surprising that Wong raised complaint in relation to Guest Bedroom because Poon never complained of water seepage in this room. Further, he did not say that the re-painting had anything to do with water seepage.

(h) 5/F Unit's patch up repairs

108. Wong opined that water ceased to drip and improvements were seen at Wong's 3rd Inspection because the following patch repairs were done at 5/F Unit, indicating that the water leakage originated there :

(a) By comparing the photographs taken for Wong's 2nd and 3rd Reports, new transparent sealant was shown to be applied to the seams between Floor Slab and the walls/sanitary fitments. Wong said it was applied 2-3 days before Wong's 3rd Inspection.

(b) Fresh white sealant had been applied to the doorframe and wall skirting of the master bedroom, indicting water seepage through the base of the partition wall adjacent to 5/F Toilet.

(c) Although not mentioned in any of his reports, Wong said that the rusty or salty water stained Flushing Valve had been replaced by the time of Wong's 3rd Inspection.

109. Lee said that if the water proof membrane or damp proof course of Floor Slab were impaired (which was Wong's main contention), the application of new sealant to the seams between Floor Slab and walls/sanitary fitments and not on the tile joints of Floor Slab would not have stopped the water leakage. Further, sealant applied to the master bedroom and other areas of 5/F Unit would not cure the problem. Sealant is mainly for making joints secure and not for water proofing. Given that Lee's reports all along excluded 5/F Unit as the origin of the water leakage, there was no reason for Choi to carry out the patch jobs as alleged.

110. Lee did not notice any replacement of Flushing Valve. Usually a plumber would replace Flushing Valve and associated piping (not just the valve) to ensure a good fit as valves and associated piping come in different shapes and sizes.

111. I accept on the balance of probabilities Choi's evidence that he had not applied new sealant to 5/F Toilet as alleged by Wong. I find it impossible to draw such inference from the photographs which were taken with different cameras, angles and distances. More importantly, I find Wong's surmise that the sealant was applied 2-3 days before Wong's 3rd Inspection unreliable. His surmise was based on his observation that sealant found at the shower cubicle showed a little peak (instead of being flat and smooth). However, if the sealant was squirted out in that shape during application and hardened, the shape of a little peak would be retained no matter how long ago it was applied. Further, Poon's evidence that improvement and cessation of water dripping at 4/F Toilet occurring 2-3 months before the trial is inconsistent with Wong's opinion that they were the result of patch-up repairs done in mid/late September 2003. Further, if there were water leakage, patch repairs at the seams of Floor Slab and walls/sanitary fitments (and not tile joints) at 5/F Toilet would not have cured Floor Slab Cause, Cistern Cause (if there was overflow from the water tank) and FWS Cause (if there was leakage in concealed FWS Pipes). Wong could not satisfactorily explain the improvement observed at 4/F Toilet during Wong's 3rd Inspection.

112. Having studied the photographs, I do not accept that Flushing Valve was replaced. Anyway, its replacement or otherwise is not material because even Wong accepted that there does not appear to be leakage from the flush water supply pipe from his visual observation.

113. P has not shown that the patch jobs contributed to the improvement observed at Lee's and Wong's 3rd Inspections. I also find on the balance of probabilities that the water leakage had ceased by that time. Had there been continuous water leakage (and noting that fresh and flush water are supplied under pressure and having found that usage of 5/F Toilet had not altered), the obvious improvement seen at Lee and Wong's 3rd Inspections could not be explained on P's case.

(i) Floor stains

114. Wong noted at Wong's 3rd Inspection that water stains were found on the teak parquet flooring of the master bedroom and the corridor adjacent to 5/F Toilet with blackened floor tiles, suggesting that a large quantity of water had seeped from 5/F Toilet under the base of the partition wall. Further, since 5/F Toilet did not have a kerb at the doorway, cleaning Floor Slab might also dampen the teak parquet flooring. The marks were not due to usage over time, otherwise the darkening of the floor tiles would happen evenly. Wong said the darkening of floor tiles near the main entrance was caused by the seepage of water under the base of the partition wall from cleaning the common area outside 5/F Unit.

115. Lee said the teak parquet flooring would darken over time due to absorption of moisture from the air and from floor cleaning. The darkening usually occurred at the corners of the teak parquet flooring as such areas were more difficult to wipe dry after cleaning. Had the teak parquet flooring had been under water attack from 1999, the damage would not be limited to dark spots but the floor tiles would have been soaked and bulged up.

116. I accept on balance Choi's evidence that sealant applied to the doorframe and wall skirting was to secure the skirting and not to prevent water seepage. This is also supported by Lee's expert opinion. Further, as there is no water source in 5/F Unit's master bedroom, such works could not have caused the improvement observed at 4/F Toilet at Lee and Wong's 3rd Inspection. Similar dark stains at the master bedroom and main entrance of 5/F Unit showed that the former was not due to water seepage from 5/F Toilet. I accept Choi and Lee's explanations for the dark sports. I reject Wong's suggestion of seepage of cleaning water underneath the partition wall from the common lobby area to the teak parquet flooring of 5/F Unit as being speculative and unsupported by primary evidence. I agree with Lee that had there been serious water seepage to the master bedroom over the years, the sealant at the skirting would not have helped and the damage would have been more extensive.

(5)FWS Cause

117. Wong did not carry out WPT for 5/F Unit's FWS Pipes, so he was unable to say whether there was any leakage. A proper WPT should be done first before deciding whether to repair FWS Pipes. But Wong said water stains observed on the ceramic tiles beneath Elbow Bracket suggested that leakage of FWS Pipes could not be ruled out. Wong said sometimes slow water leakage of FWS Pipes (eg 2-3 drops an hour) was hard to detect by WPT and the area of affection might also be difficult to identify.

118. Lee said that if there were water leakage from 5/F Unit and the water leakage started in 1999, the damage would have been more extensive as fresh water supply was under pressure. The smaller the hole/crack the higher the pressure, so even a small leakage would cause extensive damage. For the avoidance of doubt, a licensed plumber carried out 2nd WPT in Lee's presence at Lee's 2nd Inspection. Pressure was increased to 83lb/in² which remained stable without fluctuation for 2 hours, indicating no water flowed into 5/F Unit and no leakage of FWS Pipes.

119. Wong criticised 2nd WPT in that during the test the gate valve for fresh water supply to 5/F Unit ("Gate Valve") was only turned off and not dismantled. As Gate Valve had been used for many years, turning it off would not shut off the water supply completely and a small amount of water might still pass through to compensate for loss of pressure due to leakage of FWS Pipes, so the test result might not be reliable.

120. Lee explained that since pressure in 5/F Unit's FWS Pipes was increased for 2nd WPT, water would not seep through Gate Valve into 5/F Unit as water would not move from a low to high pressure area. There was no need to dismantle Gate Valve.

121. Wong accepted that fresh water supply is under pressure, so that if the pressure was increased from 75lb/in² to 83lb/in², water pressure inside FWS Pipes was higher than outside. He also accepted that in theory water moved from a low to high pressure area. But he pointed out that water pressure at Block F was not constant at 75lb/in² and would vary depending on usage of water by other occupants of the building at any particular time.

122. Lee explained that Gate Valve and the tap controlled the supply and outflow of fresh water. If either was not properly closed and there was a leak in FWS Pipes, it would lead to fluctuation in pressure. But Lee observed that pressure remained stable for 2 hours during 2nd WPT. Based on Wong's reasoning, in order to maintain such steady pressure, the water dripping from Gate Valve into FWS Pipes must be at the same speed and volume as the leakage of water through the crack/hole in the pipes, which is extremely remote.

123. With an aid of a magnifier, Wong pointed out that the pressurised gauge showed 80lb/in² instead of 75lb/in² at one photograph taken by Lee and 90lb/in² instead of 83lb/in² in another photograph. This suggested that pressure was not stable. The measuring range of the pressurised gauge from 0-100lb/in² showed 5 sub-sections, the first of which was narrower since really low water pressure was difficult to detect. On the other hand, Lee explained that the measuring range was divided into increments of 100lb/in². For the section from 0-100lb/in², there were 4 small sub-sections of 25lb/in². For over 100lb/in², each increment of 100lb/in² was divided into 5 sub-sections of 20lb/in² each. Lee confirmed that pressure was increased from 75lb/in² to 83lb/in² and remained stable for 2 hours.

124. I find on the balance of probabilities that WSD carried out 1st WPT as stated by Choi in his evidence. It is not disputed that FWS Pipes were partly concealed, so visual observation was not of particular assistance. Even Wong accepted that proper testing is by WPT. He did not suggest any other means for testing whether FWS Pipes are intact. So for WSD to write and confirm that they found no damage or leakage of FWS Pipes, it is likely that they had carried out 1st WPT.

125. I reject Wong's criticisms of 2nd WPT. Even Wong accepted that water will flow from a low to high pressure area. So when pressure in FWS Pipes was increased during 2nd CWT (irrespective of whether it was 83lb/in² or 90lb/in² which in any event was higher than 75lb/in² or 80lb/in²), water would not flow from the outside through Gate Valve to FWS Pipes. Wong suggested that pressure would fluctuate with usage of water at Block F at any particular time but he was unable to say that water pressure beyond Gate Valve outside FWS Pipes would have exceeded 83lb/in² or 90lb/in². On balance I accept Lee's evidence that the pressure remained stable for 2 hours at 83lb/in². I also agree, even if there were leakage of FWS Pipes, it would be remote for any water dripping through Gate Valve into FWS Pipes and any leakage from such pipes to be equivalent in volume and speed.

126. I therefore find that P failed to show that the results of 2nd WPT were unreliable. Further, even if the results were unreliable, Wong did not carry out any WPT but accepted that the proper way to test whether FWS Pipes were intact was by WPT. Such omission meant that there is simply no reliable evidence to say that FWS Pipes were one of the causes of the water leakage.

(6) Cistern Cause

127. Wong agreed that flush water supply to 5/F Unit is under pressure although there is no pressure in the water tank of Cistern. When water flowed into the water tank, it might push the ball valve and fittings to a wrong position causing maladjustment to the system leading to intermittent overflows. But upon re-adjustment of the ball valve, the water level in the water tank would come down to a normal level. Alternatively, there might be spillage from the top of the water tank due to jetting of flush water into the tank.

128. Wong did not observe any overflow from the water tank and he did not try to flush Cistern. But he said that the drip marks alongside Screw Bracket suggested an overflow problem with water dripping from the water tank. Such overflow could occur in any direction and once flush water was spilled on Floor Slab, it might have been removed by cleaning. Since the sanitary fitments were used everyday, such overflow could not be ruled out. However, he accepted Cistern had no crack and there was no constant drip from the water tank. He also accepted that if Floor Slab were sufficiently water proof, the overflow would have no impact at all.

129. Lee said if there was leakage from the flushing system, it would have continued and the condition would have deteriorated over the years as flush water supply was under pressure. As regards the alleged drip marks at Screw Bracket, they were rust stains from the screw nut used for affixing Cistern to the floor/wall and there was no water source. Further, even if there was overflow from the water tank, the flush water could not have overflowed to that point.

130. Wong acknowledged that the concealed section of the flush water supply pipe to 5/F Toilet was short, but it should be checked for leakage. If there were no leakage, no repairs would be required. However, he could not observe any leakage.

131. Lee said there was no problem with the flush water supply pipe which passed through the external wall (4-5 inches) to Cistern. If it were leaking, flush water would drip to the ground floor which would be noticed by Manager or become the subject of complaint. But no such drip marks were seen on the external wall. Lee did not exclude the possibility that the flush water drainage pipe might have oxidised (not leaking) as it was exposed to the air when it passed through the external wall, such oxidisation being a common occurrence. But it would not have effect on the water leakage problem if, as Wong alleged, Floor Slab Cause was the main cause.

132. Wong's main premise was that the flush water overflowing from the water tank of Cistern leaked through Floor Slab to 4/F Ceiling. In my view, there is simply no evidence of any malfunction of the flushing system. Such problem was not stated in any of Wong's 1st, 2nd and 3rd Reports. Wong did not give any evidence that he inspected the water tank and the ball valve system. Indeed, he had not even attempted to flush Cistern. I find Wong's overflow argument speculative and unreliable. Further, from the photographs, I cannot see how overflow of the water tank would have caused the marks at Screw Bracket which had no water source and was tucked under the toilet bowl. I find Lee's explanation for the marks more plausible. In any event, I have found that P was unable to show that Floor Slab was not intact or water proof. Therefore, had the overflow argument been accepted, such overflow was not shown to have caused/contributed to the water leakage problem. I find on the evidence that Wong had not even begun to show that there was any problem with the concealed flush water pipe.

(7) Other matters

(a) Condensation at 4/F Unit

133. Wong said small quantity of condensation from normal usage of 4/F Toilet would easily evaporate and was insufficient to give rise to water leakage. When 4/F Toilet was not in use, the temperature and moving air would cause the water vapour to blow away from 4/F Ceiling. On the other hand, Lee said that the peeling and blistering paint at 4/F Ceiling was caused by lack of maintenance and condensation from normal use over a long period, which had nothing to do with water leakage.

134. I accept that condensation was not the cause of the water leakage. However, I find on balance that over 20 years, the condensation from normal usage of 4/F Toilet did contribute to the peeling and blistering of paint at 4/F Ceiling.

(b) External Wall Cause

135. Wong said that during all 3 inspections, the weather was fine and there had been no rain for a long period of time (Wong checked with the Government Observatory although such data was not recorded in his reports). Wong observed that there were no live watermarks on the external wall at Wong's 1st Inspection (but reported in Wong's 3rd Report), therefore he assumed water did not seep through the external wall. By Wong's 3rd Inspection, EW Renovation was completed and Block F was patched up with new plaster and re-painted. Although an old building, Block F appeared to be in good condition with no defects on the external wall outside 4/F and 5/F Units. Had the external wall caused the water leakage, Wong expected that more flats in Block F to be affected. Poon told him that there were no such complaints from 4/F and 5/F Units. But Wong accepted that other flats might have external wall problems.

136. Wong opined that the water source was confined to 5/F Unit because 5/F Ceiling was dry and water passes from high to low level. Hence the water leakage was due to percolation from 5/F Toilet. Wong had not seen cases of water attack from an upper floor on a lower floor without affecting the floor in between. Each floor's ceiling slab was attached to the external wall, so watermarks should appear on the ceiling of each intervening floor if there was water leakage.

137. The dampness was concentrated on 4/F Ceiling and the ceiling of Master Bedroom without seepage at the window frame. Further, Poon first observed a water stain at 4/F ceiling above the washbasin. Wong therefore ruled out the ingress of atmospheric water as a possible cause. If there was seepage through the external wall due to capillary action, Wong expected the water stain at 4/F Ceiling to extend from the external wall in a half moon shape. But under cross-examination, he accepted that such shape depends on the location and extent of the defects on the external wall. A half moon shape would normally appear if the whole length of the external wall corresponding to 4/F Ceiling was leaking or if there were small areas of large defects on the external wall.

138. Although Wong accepted that water would first attack weak points in the ceiling which could occur anywhere, such theory did not apply to the external wall which was vertical, so a large volume of rainwater would flow along the surface downwards. The water paths were different. Further, if the weak points were small, rainwater would be absorbed by the external wall. For water leakage to affect the flats, the cracks at the external wall would have to crack through to the flats.

139. Since Wong found chloride at 4/F Toilet and rainwater did not carry chloride, rainwater was not causative of the water leakage. Wong found some old watermarks on the waste water drainage pipe on the external wall, which was the result of the normal phenomenon of aging and weathering.

140. At Lee's 1st Inspection, he observed the external wall from the windows of 4/F and 5/F Toilets but did not note any apparent defects. Poon informed Lee that the water leakage/dampness occurred even on sunny days, so Lee stated in Lee's 1st Report that the water leakage was not from rainwater seepage. Lee said in evidence that apart from rainwater, another possible cause of water seepage was the drain at the external wall bracket. He only posed this as a possibility which was not mentioned in his reports because his brief was not to find out the cause of the water leakage. Further, although he did not observe any visible defect at the external wall of 4/F and 5/F Toilets, he could not rule out defects for the whole of Block F.

141. Lee said the water stain pattern at 4/F Toilet remained the same for over 11/2 years and in fact the water leakage had ceased by Lee's 3rd Inspection. Since D had not done anything to 5/F Toilet that materially affected any water leakage and the only repair works were IO's EW Renovation, the most probable cause of the water leakage was rainwater seepage through cracks in the external wall to 4/F Ceiling, which cause was at some stage cured or minimised by EW Renovation, so the water stain pattern at 4/F Unit no longer deteriorated. The key was not when EW Renovation was completed but when the water leakage points on the external wall were repaired and patched up.

142. Lee disagreed that seepage from the external wall would necessarily result in a half moon shaped water stain. Water seepage depended on the presence of cracks on the external wall that allowed entry of water and on the water paths through the concrete to the plaster. If the plaster was well made, then the water would spread along the area between the concrete and plaster and become a half moon shape from the centre point of the leakage. Otherwise water stains came in different shapes. The half moon shape was not confined to leakage from the external wall.

143. Lee said leakage from the floors above 5/F Toilet is another possible cause of the water leakage but he could not confirm this because he had no access to those flats for inspection. But he had experience in another case of water leakage from an upper floor to a lower floor without any attack on the floor in between.

144. It should be remembered that it is not for D to prove that External Wall Cause was the cause of the water leakage. However, if External Wall Cause is shown to be a real possibility and not excluded on the balance of probabilities, then P may well be in difficulty in establishing liability. Poon accepted that D was not liable for water seepage through the external wall.

145. RCSL's Reports indicated quite clearly that there were problems with external wall seepage at HB Centre for which Building and EW Renovations were required. RCSL's 2nd Report reported on the Pull-off Testing undertaken by Testconsult. It showed inter alia that the main external wall of 4/F of Block F failed the test at tile/adhesive interface, indicating possible problems with bond strength. It is common ground that Block F also carried out EW Renovation. But IO elected to carry out patch repairs by tile filling and re-painting, so it is unclear whether all problem areas were repaired. Whilst it is true that Lee's 1st Report excluded External Wall Cause, he was then reliant on Poon's information in coming to that view and at that time he did not have the benefit of information in relation to EW Renovation.

146. I also accept on the balance of probabilities Choi's evidence that EW Renovation was only completed upon re-painting of Block F subsequent to March 2002 (by which time only tile filling was done).

147. I do not accept Wong's claim that seepage from the external wall must be in a half moon shape. Other than a reference to capillary action, he was not able to explain why it must be so. Rather I find Lee's explanation logical and sensible and I find that the shape of water stain from external wall seepage depends on the extent and location of the defects. If there were defects on the tiling or concrete of the external wall which is exposed to the elements, rainwater seepage is inevitable. I find that I cannot accede to Wong's opinion that rainwater would largely flow vertically downwards along the surface of the external wall or be absorbed by the external wall without seepage. RCSL's Reports spoke clearly of problems of water seepage from the external wall where there were defects on the walls. I accept Lee's opinion that water will simply follow weak points and cracks and find its own water path.

148. Further, Wong's reliance on chloride testing to exclude rainwater seepage is difficult to understand for even on his contention, there is fresh water attack at 4/F Toilet as well. In any event, I have found that the presence of chloride may well be due to chloride leaching from concrete. I therefore find on balance that rainwater seepage through the external wall remains a live possibility on the present evidence as a cause for the water leakage.

Conclusion

149. By reason of the above matters, although I sympathise with P's position, I find that she has not sufficiently discharged the burden of proof on the balance of probabilities to show or to enable the court to draw the inference that the water leakage originated from 5/F Unit. Wong posed a large number of possibilities but no serious efforts had been made to verify such possibilities or to properly identify the true cause(s) of the water leakage. Quite often, Wong projected the reason simply from the manifestation of signs of water leakage and lost sight that the various causes have to be properly shown to lead to the water leakage. I find his approach unreliable.

150. I also find that D as owners of 5/F Unit had taken reasonable and appropriate steps to respond to P's complaints. D not only asked Contractor to inspect the 2 units, they allowed inspections and tests by FEHD and WSD, responded to the Manager's letters, allowed Wong to inspect 5/F Unit before any court order was granted, requested for re-testing by FEHD and offered to have a joint independent survey. More importantly, Choi clearly indicated that D would carry out repairs if it were shown that 5/F Unit caused the water leakage.

151. As P failed to establish any liability on D's part in respect of the water leakage, I find it unnecessary to consider the evidence led by the parties on the issue of damages. In the circumstances, I dismiss P's claim. There is no reason why costs should not follow event. I therefore order that P do pay D costs of the action (and all costs reserved) to be taxed if not agreed with certificate for counsel. Mr Tam, solicitor for P, made submissions to oppose certificate for counsel (if the court is minded to grant a costs order nisi to that effect). However, I find that the case is of some complexity, involving both lay and expert evidence, and I have been assisted in this matter by counsel's involvement. I therefore consider it appropriate in this case to grant certificate for counsel.