CHOW CHI YI v. POON TAK LUN (also known as 潘德鄰)

DCCJ 3293/2023

[2026] HKDC 502

IN THE DISTRICT COURT OF THE

HONG KONG SPECIAL ADMINISTRATIVE REGION

CIVIL ACTION NO 3293 OF 2023

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DECISION

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A.  INTRODUCTION

1.  This is the appeal of the Plaintiff (“P”) against the decision of Master YH Chan (the “Master”) dated 23 June 2025 which granted leave to the Defendant (“D”) to adduce D’s own expert report following the submission of a single joint expert report.

2.  In this action, P claims damages arising from (1) water seepage in the bathrooms of P’s unit since February 2022 (the “Seepage”) and (2) the breaking of a saltwater pipe at D’s unit on 8 June 2023 when D’s contractor was performing repair work. The expert evidence, and consequently the current application, pertain exclusively to the first claim.

B.  FACTUAL BACKGROUND

3.  Both P’s unit and D’s unit are residential premises at Whampoa Garden. D’s unit is situated directly above P’s unit. Both units share identical layouts, featuring a guest bathroom located in one corner and a master bathroom adjacent to it; both bathrooms are positioned against an external wall.

4.  Prior to the present proceedings, several contractors were engaged to identify the source of the water seepage, namely:

4.1  Two contractors, Modern Testing Consultants Ltd (“Modern”) and C&L Architects & Surveyors Limited (“C&L”), were appointed by the Buildings Department and the Food and Environmental Hygiene Department Kowloon Regional Joint Office (the “Joint Office”). Modern issued a report dated 27 January 2023. C&L issued a report dated 12 May 2023.

4.2  Two contractors, Citiland Surveyors Limited (“Citiland”) and Hong Kong Survey Limited (“HKSL”), were engaged by P. Citiland issued a report dated 20 January 2023. HKSL issued a report dated 22 March 2023.

4.3  D instructed John HY Yip Surveyors Ltd (“John Yip”). John Yip produced a draft report dated 21 July 2023 (“John Yip’s Draft Report”)[1] and a final report dated 8 January 2024 (“John Yip’s Final Report”).

5.  As a result of the Seepage, the Joint Office issued two nuisance notices to D:

5.1  The 1^st Nuisance Notice dated 13 February 2023 required D to carry out repairs to the master bathroom floor.

5.2  The 2^nd Nuisance Notice dated 22 May 2023 required D to repair the floor slab, including the enclosing walls of the shower area of the guest bathroom and the drainage pipe(s) connecting to the water closet of the guest bathroom.

6.  In the meantime, during the period between 2022 and 2023, extensive repair works were undertaken at both premises. By the time the single joint expert subsequently conducted an inspection on 9 August 2024, renovations to P’s unit had been completed, while works at D’s unit were ongoing. As such, the condition of the units during the inspection differed from their state at the time of the 2022 seepage incident. Accordingly, the single joint expert’s evaluation is predominantly informed by a desk review of reports prepared by contractors who examined the premises prior to the repairs.

C.  PROCEDURAL HISTORY

7.  During the Case Management Summons Hearing on 28 May 2024, Master Ross Li directed the parties to appoint a single joint expert as nominated by the Hong Kong Institute of Surveyors to adduce a single joint expert report, giving opinion on the following issues:

7.1  the source and cause of the Seepage, including whether the Seepage originated from the D’s unit;

7.2  P’s loss and damages caused by the Seepage (if any); and

7.3  the remedial works necessary to be carried out to restore P’s unit and the costs of such work.

8.  The Hong Kong Institute of Surveyors nominated Mr Samson Wong as the single joint expert (the “SJE”) on 17 June 2024.

9.  Relevant documents, including reports from the aforementioned contractors, were submitted to the SJE. D’s solicitors, however, inadvertently provided John Yip’s Draft Report to the SJE instead of the Final Report. The SJE issued a report dated 19 September 2024 (the “"SJE Initial Report”). Following discovery of the said mistake, John Yip’s Final Report was provided by D’s solicitors to the SJE, who then issued a further report dated 14 October 2024 (the “SJE Supplemental Report”). It was the SJE’s opinion that the Seepage originated from D’s unit to P’s unit.

10.  On 6 December 2024, D filed a summons seeking leave to adduce a second expert report (the “Application”). In support of his application, D commissioned Mr Lee Hoi Tat Nathan of Ample Surveyor Services Limited (“Nathan Lee”), who provided a draft report dated 3 February 2025 (“Nathan Lee’s Report”).

11.  The Application was heard by the Master on 23 June 2025, who granted the Application. Following this decision, P lodged a Notice of Appeal dated 4 July 2025, contesting the Master's ruling.

D.  D’S REASONS TO ADDUCE A SECOND EXPERT REPORT

12.  D has raised extensive criticisms regarding the SJE. The recurring themes within these criticisms include contentions that the SJE’s reasoning is overly simplistic, that the SJE did not adequately engage with John Yip’s analysis, and that there are matters overlooked by the SJE.

13.  Generally, these critiques can be grouped into three main categories:

13.1  The SJE should not have rejected D’s case that there was no water usage by D after 25 February 2022 and that D vacated D’s unit after 17 March 2022 (“Complaint Category 1: Water Usage”).

13.2  The SJE should not have dismissed the external wall as a potential source of seepage despite finding that there might be defects on the external wall (“Complaint Category 2: External Wall”).

13.3  The SJE should not have uncritically accepted the quantity of repair items listed in the quotation provided by P’s contractor which carried out the relevant repairs (“Complaint Category 3: Quantum”).

E.  LEGAL PRINCIPLES

14.  The principles on admission of an additional expert following the appointment of a single joint expert are set out in Daimler AG v Leiduck [2014] 3 HKLRD 56 at §§32-34:

“32. The appointment of a single joint expert (SJE), whether by agreement between the parties or imposed by the Court, does not per se bar a party from seeking leave to instruct its own expert to challenge the SJE’s evidence or aspects thereof.

33. Leave should and would be granted if, upon balancing all relevant considerations, it is just and accords with the underlying objectives of Civil Justice Reform (as set out in the Rules of the High Court (Cap.4A, Sub.Leg.) O.1A r.1) to do so. See Daniels v Walker [2000] 1 WLR 1382 (CA), per Lord Woolf MR at 1386H and L v L (unrep., HCMC 1/2003. [2005] HKEC 1851) (20 April 2005), per Johnson Lam J (as he then was) at [22] and [25]. See also Hodgkinson, Expert Evidence: Law and Practice (3^rd ed., 2009), p.158 para.5-005.

34. In Cosgrove v Pattison [2001] CP Rep 68, Neuberger J identified nine factors for consideration in deciding whether to allow the evidence of a second expert, in addition to the evidence of an expert instructed jointly, under Civil Procedure Rules 1998 Part 35:

(1)  the nature of the dispute;

(2)  the number of disputes on which the expert evidence is relevant;

(3)  the reason for requiring the second report;

(4)  the amount at stake or the nature of the issues at stake;

(5)  the effect of permitting a second expert report on the conduct of the trial;

(6)  the delay in making the application;

(7)  the delay that might be caused in the conduct of the proceedings;

(8)  any other special features;

(9)  the overall justice to the parties.”

15.  A mere difference in opinion between experts is not a sufficient reason without more to adduce a second expert report: Redland Precast Concrete Products (China) Ltd v AES Steel Mould (Hong Kong) Ltd [2021] HKCA 1229 at §13:

“13. The first two grounds attack the judge's view that the plaintiff has failed to demonstrate sufficient grounds for adducing its own expert report in addition to the SJE's opinion. In particular, it was submitted that the test is whether there are "not fanciful" reasons for the plaintiff to call another expert notwithstanding an SJE has been appointed, and that the fact that there is a materially different opinion from an expert of the same level of expertise as the SJE is such a "not fanciful" reason. We are unable to accept this submission. The reason for the party concerned to want to put forward a second expert report (and it is unnecessary to decide whether it has to be a non-fanciful reason or a good reason) is simply one of many factors to be considered in the exercise of the court's discretion, which is ultimately guided by the interests of justice and the underlying objectives of the procedural rules as set out in Order 1A rule 1 of the Rules of the High Court (Cap 4A): Daimler AG v Leiduck (re: expert evidence) [2014] 3 HKLRD 56 , §§33-34; Dennis Kwok Hon Ming v Poon Sui Cheong Albert & others HCMP 1526/2013 (29 December 2017), §§15-20. The presence of such reason is not conclusive. The “test” suggested by the plaintiff would mean that a litigant could always adduce its own expert evidence, despite the appointment of an SJE, so long as he could find an expert who took a materially different view. That does not seem to us to be correct.”

16.  The “test” for permitting additional expert evidence has been the subject of judicial consideration. In the case of Daimler, Recorder Lisa Wong SC (as she then was) observed at paragraphs §§35-36:

“35.  With regard to the reason for requiring own-party expert evidence, in Daniels v Walker, supra, Lord Woolf MR held (at 1387E) that additional expert evidence may be permitted where the dissatisfied party’s reasons for wishing to adduce such evidence are “not fanciful”. The same Judge then seemed to suggest, obiter, a more stringent test in Peet v Mid-Kent Healthcare Trust [2002] 1 WLR 210 (CA) at [28], in that “good reasons”, as opposed to “reasons which are not fanciful”, must be shown.

36.  In L v L, supra, Lam J was referred to both cases and the language of [17] of his Lordship’s judgment appears more consistent with a preference for the “not fanciful reasons” test in Daniels v Walker. Further, it is observed in Hodgkinson, Expert Evidence: Law and Practice, supra, p.158 at footnote 34 that the later dicta was probably per incuriam. The distinction seems to me to be a fine one. I do not think the application before me would turn on which of these tests should be followed. However, I am inclined to think that, for what is essentially a case management decision to be made to achieve justice and upon balancing all material factors of which the reasons for challenging the SJE’s opinion is but one, it should be sufficient if those reasons are not fanciful, particularly if the other considerations also point to own-party expert evidence being appropriate.”

17.  While the “non-fanciful” test may initially appear to advantage D, Mr Law Ka Sing, counsel for D, fairly referenced Zvonko Bulic v Harwoods & Ors [2012] EWHC 3657 (QB). In that case, Eady J emphasised that the various “tests” should not be interpreted as if the terminology employed carries statutory weight, and that the ultimate aim is to achieve overall justice to the parties (at §§11-17):

“11. There was much argument on whether the Judge had applied the right "test”. In developing the first ground, Mr Murray placed reliance upon the judgment of Lord Woolf in Daniels v Walker at p.1387D-E:

“…Where a party sensibly agrees to a joint report and the report is obtained as a result of joint instructions in the manner which I have indicated, the fact that a party has agreed to adopt that course does not prevent that party being allowed facilities to obtain a report from another expert or, if appropriate, to rely on the evidence of another expert.

In a substantial case such as this, the correct approach is to regard the instruction of an expert jointly by the parties as the first step in obtaining expert evidence on a particular issue. It is to be hoped that in the majority of cases it will not only be the first step but the last step. If, having obtained a joint expert's report, a party, for reasons which are not fanciful, wishes to obtain further information before making a decision as to whether or not there is a particular part (or indeed the whole) of the expert's report which he or she may wish to challenge, then they should, subject to the discretion of the court, be permitted to obtain that evidence.”

Significance has been attached in the course of argument to the words “substantial case such as this” and also to the phrase “reasons which are not fanciful”. Mr Brennan argues that Judge Simpkiss was entitled to hold that this case was not sufficiently “substantial”, by comparison with the circumstances in Daniels v Walker, to justify Mr Cookson being disinstructed. Mr Murray, on the other hand, points to the phrase “not fanciful” in suggesting that the Judge applied too strict a test when assessing the Appellant's qualms about Mr Cookson's reasoning and expertise.

12.  This passage in Lord Woolf’s judgment was cited by the Judge and he clearly took it into account. He also referred to other decisions, including Cosgrove v Pattison [2001] CPRLR 177, a decision of Neuberger J (as he then was), and Kay v West Midlands Strategic Health Authority, unreported, where there was a full analysis of the relevant authorities by His Honour Judge MacDuff QC (as he then was). A passage from this judgment was quoted by Judge Simpkiss as follows:

“Where a party requests a departure from the norm and makes what one can term a Daniels v Walker application, all relevant circumstances are to be taken into account but principally the court must have its eye on the overall justice to the parties. This includes what I have called the balance of grievance test. The application will only succeed in circumstances which are seen to be exceptional and to justify such a departure from the norm.”

It was with reference to these words that Judge Simpkiss observed that Judge MacDuff was there setting out the “correct test to adopt” and that he did not regard it as being in any way inconsistent with the passage cited above from Lord Woolf’s judgment.

13.  It was this approach which has been criticised by Mr Murray on the basis that he regards the words of His Honour Judge MacDuff as giving rise to a “narrower test of exceptionality”, because in order to obtain another expert report an applicant's reasoning should only have to pass the test of being “not fanciful”. The Judge should have asked, therefore, according to Mr Murray, not whether the circumstances were “exceptional” but merely whether the Appellant’s concerns about Mr Cookson’s evidence could be characterised as “fanciful”. He argues that there was thus an error of law and that the Judge should have applied Lord Woolf’s “test” without adding the “varnish” to be found in Judge MacDuff’s words.

14.  Reference was also made to another decision of the Court of Appeal, to which Lord Woolf was a party, in Peet v Mid-Kent Healthcare Trust (Practice Note) [2002] 1 WLR 2010. This too had been fully considered by Judge MacDuff in Kay. It was a personal injury case which gave rise to the issue of whether or not a conference could be conducted by the claimant in the presence of the joint experts without the consent of the defendant. The facts are clearly a long way from the present circumstances, but in the course of the judgments some relevant remarks were made more generally about the instruction of single joint experts. In particular, at [28], Lord Woolf CJ made the following comments:

“… The starting point is: unless there is reason for not having a single expert, there should be only a single expert. If there is no reason which justifies more evidence than that from a single expert on any particular topic, then again in the normal way the report prepared by the single expert should be the evidence in the case on the issues covered by that expert's report. In the normal way, therefore, there should be no need for that report to be amplified or tested by cross-examination. If it needs amplification, or if it should be subject to cross-examination, the court has a discretion to allow that to happen. The court may permit that to happen either prior to the hearing or at the hearing. But the assumption should be that the single joint expert's report is the evidence. Any amplification or any cross-examination should be restricted as far as possible. Equally, where parties agree that there should be a single joint expert, and a single joint expert produces a report, it is possible for the court still to permit a party to instruct his or her own expert and for that expert to be called at the hearing. However, there must be good reason for that course to be adopted. Normally, where the issue is of the sort that is covered by non-medical evidence, as in this case, the court should be slow to allow a second expert to be instructed.”

15.  I cannot help thinking that the argument has been diverted on to a detailed analysis of various "tests” as though some of the phrases used were of statutory significance. I believe that Lord Woolf would be surprised to find that such an apparently legalistic approach was being adopted 13 years after the advent of the CPR. No straitjackets were intended. In referring simply to requiring a “good reason” in one case may prove quite inadequate in another. None of these judicial observations, uttered in the context of applying broad principles to very specific factual circumstances, should detract from the breadth of the court’s discretion or from the general terms in which the guidance was given in the earlier cases.

16.  The importance of the overriding objective was often emphasised. Judge MacDuff, for example, referred to "overall justice to the parties”. Moreover, Lord Woolf stressed the point in Daniels v Walker at p.1386H:

"If, having agreed to a joint expert's report a party subsequently wishes to call evidence, and it would be unjust having regard to the overriding objective of the CPR not to allow that party to call that evidence, they must be allowed to call it.”

What represents justice between the parties will very much depend upon the facts of each case. For that reason, it can be distracting to focus too analytically on the reasoning in other cases, however authoritative, where the facts were not truly comparable. There are different factors to be taken into account and the importance of each is likely to vary according to the particular facts. For example, the saving of time and money is likely to assume greater significance in inverse proportion to the centrality of the issues. Where the court is concerned with a relatively "peripheral” issue, as in Kay, it is likely to be only in unusual circumstances that the services of a single joint expert will be dispensed with: see e.g. at [35]-[36].

17.  So too, the court is less likely to be ready to dispense with a single expert where the evidence is of a non-technical nature, as Lord Woolf explained in the last sentence of the passage cited above from Peet. (I part company with Judge MacDuff where he held that Lord Woolf used "non-medical” when he must have intended to say simply "peripheral”. I will take the word at face value.)”

F.  ANALYSIS

F1.  Appropriateness of Clarifications

18.  One of the general arguments of Mr Michael Leung, counsel for P, against adducing a second expert report is that clarifications should be sought from the SJE instead. Whether clarifications are appropriate will be further considered in relation to each of D’s criticisms below. Here, I will address Mr Law’s general arguments against clarifications.

19.  I acknowledge Mr Law’s submission that a second expert report is not necessarily limited to being a “last resort”. However, when suitable, seeking clarifications or elaborations from the existing expert is generally likely to incur significantly lower costs compared to engaging another expert. Accordingly, if any issues with the existing expert’s report can be adequately addressed through clarification or elaboration, it will seldom be reasonable to permit the higher expenses entailed in calling a second expert (and potentially a third, should the other party also seek and be granted leave to file his or her own expert report).

20.  Mr Law has also submitted that in response to a request for clarifications, if the SJE does not change his opinion, then D would have even stronger grounds to apply for a second expert, while if the SJE does change his opinion, then that would constitute grounds for criticising the SJE’s reliability. With respect, I disagree. First, this argument applies to all instances of clarifications and seems to suggest that clarifications are never appropriate, which must be incorrect. Second, the fact that the SJE does not change his opinion after clarification would not automatically constitute grounds to apply for a second expert. An answer that D does not like is not necessarily an answer that is unsatisfactory. Third, the mere existence of scope for clarification or amendment does not necessarily mean the SJE would be regarded as unreliable in the first place; rather, it can reflect a proper and expected willingness to rectify any ambiguities or identified errors.

21.  Mr Law has also noted at multiple points that the SJE has had two opportunities to consider John Yip’s analysis, since the SJE had the opportunity to consider both John Yip’s Draft Report and John Yip’s Final Report. The point seems to be that there is little reason to seek clarifications since the SJE has already been given a second chance. I also do not accept this argument. The point of clarifications is to formulate questions to direct the SJE to deal with specific issues. Just presenting John Yip’s opinion twice, once in draft form and once in final form, does not achieve that objective.

F2.  Complaint Category 1: Water Usage

22.  It appears that D seeks to argue that D’s unit could not have been the source of the Seepage, in part because there was no water consumption at D’s unit’s bathrooms and the water supply had been turned off and/or cut off while the Seepage persisted.

23.  According to D:

23.1  On 25 February 2022, D procured the water supply mains of D’s unit be switched off and had not used potable water in the unit since then.

23.2  On 17 March 2022, D switched off the flush water main valve and moved out of D’s unit.

23.3  Between 21-24 March 2022, D engaged Mei Fai Construction Engineering Co. (“Mei Fai”) to conduct works to cut off the potable water pipes of the guest bathroom of D’s unit.

F2.1  “No Competent Person”

24.  §§17-18 of the SJE Initial Report reads:

“17. I note that the Defendant denied residing at the Defendant’s premises and stated that they turned off the main valve of the flush water pipes on 17 March 2022. Additionally, from 21 to 24 March 2022, they conducted work to cut off the potable water pipes in the Secondary Bathroom. The shower area of the Secondary Bathroom was being used for storage purposes and should not be subjected to a ponding test.

18. My reservations on the above statements are that no competent person was appointed to handle the anti-leakage measures and confirm that whether the actions mentioned had effectively stopped the water seepage at that moment.”

25.  My impression from the above is that the SJE’s key point was simply that no one – whether Mei Fai or anyone else – had investigated or confirmed whether the Seepage had in fact been effectively stopped following D’s alleged actions. D’s criticisms instead focused on the SJE’s reference to a “competent person”. D argues that the SJE was wrong because (1) Mei Fai conducted works to cut off the potable water pipes between 21-24 March 2022 and (2) Mei Fai is a “competent person” as it possessed the relevant qualification. However, Mei Fai neither undertook general anti-leakage works nor confirmed that the leakage had already been stopped “at that moment”. Whether Mei Fai is competent is therefore beside the point. Insofar as there is ambiguity in what the SJE meant, I see no reason why that cannot be dealt with by way of clarification.

26.  Nathan Lee’s Report also referred to an inspection by John Yip, a “competent person”, on 14 December 2024. However, this inspection was conducted way afterwards, after extensive repair works had been done to both units. Accordingly, the inspection is not relevant to the condition of D’s unit in 2022.

F2.2  Water Bills

27.  To demonstrate no water usage, D has produced a number of water bills. These are relevant only to potable water usage as the use of flush water is free.

28.  John Yip’s Final Report at §6.1 reads:

“According to the verbal evidence provided by the Owners of Flat I SF, water supply of water for Flat I SF had been suspended since receiving the first complaint. No water was consumed from 14 May 2022 to 17 January 2023 as recorded in the water bill provided by the Owners of Flat l SF.”

29.  The SJE’s analysis on the above is at item 1 of the table at §9 of the SJE Supplemental Report, which reads:

“According to John Yip's Report para 6.1, Defendant made a verbal statement that no water was consumed from 14 May 2022 to 17 January 2023. The lack of change in the water meter readings was not valid supporting evidence to demonstrate that the defendant had no water consumption. In fact, Defendant has maintained low water consumption from the WSD water supply for more than 10 years. According to the bill provided by WSD on 20/5/2022, it is shown that the last payment was 27/2/2012…

The consumption history simply indicated that the Defendant might have a very low level of water consumption but not the water supply system is totally leak-proof….

Furthermore, the WSD bill could not reflect the consumption habits of the flush water supply…”

30.  Mr Law criticised the SJE’s “rejection” of D’s case that he had moved out from his flat and therefore had no water consumption. However, I do not think the SJE’s opinion can be interpreted as a rejection of D’s case. It seems the SJE was simply indicating that D’s case was not backed by the produced water bills, not that D’s factual case was disbelieved or that it must be wrong.

31.  That said, in the analysis of the water bills, it does appear that the SJE did not consider some potentially relevant information. Whist the SJE has considered the water bills and analysed the water usage for D’s unit before 14 May 2022 which show some usage, he did not seem to have analysed the water bills for the period from 14 May 2022 to 17 January 2023 which apparently suggest zero water usage.

32.  Mr Leung made the following points in defence of the SJE:

32.1  Mr Leung submitted that D did admit, in his supplemental witness statement, that water had been used for testing purposes on 30 March 2023[2], and accordingly (assuming the SJE did “reject” D’s case) there is no basis to criticise the SJE, since the SJE was correct. However, 30 March 2023[3] is not within the period between 14 May 2022 to 17 January 2023 being discussed and so water usage on that date is not directly relevant.

32.2  Mr Leung also submitted that the water usage on 30 March 2023 was very low such that only the decimal places of the water meter (which measures water usage in cubic metres) moved. It appears the argument is that water can be used without it showing up on the water bills, because the water bill only records water usage when the water meter ticks over to the next cubic metre. However, the argument does not seem to be backed by enough objective evidence.

32.3  Mr Leung also argued that a small amount of water may be used for free as a reason why water usage may not show up in water bills. However, I think the issue is whether any water was used, not whether any money was charged. The water bills appear to show that even if water consumption falls below the point at which a fee is levied, the usage is still recorded.

33.  Nevertheless, it seems that this issue can also be resolved by asking the SJE to elaborate on what he has to say about the recorded lack of water usage in the water bills for 14 May 2022 to 17 January 2023. Queries can also be made about whether there are rounding practices on water bills as contended by P.

F3.  Complaint Category 2: External Wall

34.  D contends that a possible source of the Seepage is the external wall, and the SJE was wrong to reject that possibility.

F3.1  General Lack of Elaboration

35.  D criticised the SJE for failing to elaborate why defects to the external wall were not causes of water seepage. The key paragraphs of the SJE Initial Report in relation to this criticism are §§19-20, which read:

“19. The Defendant also raised out the other possibility of water seepage from external wall. The Defendant engaged John Yip to conduct a study on the case. According to the John Yip’s draft report, he believed that the bathrooms had been used as a storeroom, and water usage had been suspended since 14 May 2022. He further believed that the water source claimed to be causing water seepage at the Plaintiff’s premises was originated outside the bathrooms of the Defendant’s premises supporting the possibility of water seepage from the external wall.

20. In my opinion, there were two key issues: firstly, no supporting test was conducted on the external wall to substantiate this argument. Secondly, John Yip did not properly sign and endorse the draft report, which raises doubts about completeness of his final opinion and judgment in this case.”

36.  Contrary to D’s criticism, I think the SJE has elaborated on why he did not find sufficient evidence to establish the external wall as a cause of water seepage. He points out that no test was done to determine whether the external wall was the source of the water seepage. The point is that there is no basis for the SJE to comment on whether the external wall is or is not a source of the seepage, precisely because there is no evidence from a supporting test either way.

F3.2  Lack of Water Spray Test

37.  Another complaint from D is that the SJE had believed that the Seepage did not come from the external wall simply because no spray test was conducted, effectively putting the burden on D to prove leakage from the external wall.

38.  The key paragraph of the SJE Supplemental Report in relation to this issue is item 2 of the table at §9, which reads:

“In normal practice, if water seepage is suspected likely from the external wall, a water test for the external wall should be conducted to verify the assumption.

Through the photo records, I agree that there might be defects observed on the external wall; however, the expert has made no effort to identify the severity of the defects or determine whether they had a direct relationship with the water seepage issues.

Unfortunately, neither a close examination of the possible water path nor conducting water test on the external wall was done in the previous investigation by the expert, and furthermore, subsequently, certain comprehensive repair works were carried out, which covered up the whole area in dispute.”

39.  Mr Law submitted that the lack of a spray test does not prove anything either way. However, I think the SJE did not make any factual conclusion or say that it was impossible that the water seepage came from the external wall. He simply noted that there was no test to substantiate the relationship between the defects and the seepage.

40.  Further, Nathan Lee’s Report at item 2(i) of the table at §6.1.2 simply notes that there is also no water spray test by Citiland, Modern, HKSL, C&L, or the SJE, and therefore it is impossible to confirm or rule out the potential of water seepage from the external wall. That opinion does not contradict what the SJE stated.

41.  At the hearing, there was some discussion of a spray test that the building management, Whampoa Garden Management Limited, had done on 13 May 2022. Mr Law submitted that the prior reports, including the SJE’s, had missed that a spray test had been done. However, Mr Leung submitted that the spray test was done on the other side of P’s unit, on the external wall outside the living room (客廳外牆). Mr Law later appeared to dispute that assertion but did not point to any further supporting documentation. Having looked at the record of the spray test and the plan of P’s unit, it does appear to me that the management spray test was done on a different part of P’s unit.

F3.3  Chloride and Ammonia

42.  Another of D’s complaints concerns the chloride and ammonia content detected by HKSL in a water sample analysis. John Yip’s Final report at §7.9 states the following:

“The test result stated that chloride and ammonia were found and defined the water seepage source should be the upper-level's drainage pipes. However, the collected sample from bathroom ceiling means that the water source might have gone through unknown area, such as plastering/concrete substrate of wall/slab, etc, and might be contaminated by those substant in bathroom. This limitation should be noted which may lead to false statements on the water seepage source.”

43.  The purpose of this comment is to show that the Seepage could have come from a source other than flush water. The possible sources of non-flush water are the potable water supply and the external wall. D is obviously arguing against the Seepage coming from the potable water supply, having adduced water bills to show no potable water usage. Further, if the Seepage originated from D’s potable water supply, then D would still be liable. Accordingly, the relevance of this point seems to be to show that the Seepage could have originated from the external wall notwithstanding the chloride and ammonia detected.

44.  At item 4 of the table at §9 of the SJE Supplemental Report, the SJE comments the following:

“In addition to the Water Sample Analysis, HKSL also conducted visual inspections, infrared scans, electrical conductivity sensing, microwave scans, and flow meter tests to support their findings and opinions. The water sample results, which contained chloride and ammonia, serve as supporting evidence to conclude that one of the water sources through the drainage system.

Furthermore, John Yip only expressed doubts about the source of chloride and ammonia, but he had no other supporting evidence to substantiate the suspected source of contamination.

More often, if there is water seepage from the soil and waste drainage system, chloride and ammonia would be detected in the Water Sample Analysis”

45.  In short, the SJE’s comments are to the effect that, (1) the water sample results was only one of multiple pieces of evidence that led HKSL to conclude that the water came from the drainage system, (2) John Yip did not provide any supporting evidence to substantiate the suspected source of contamination, and (3) seepage from soil and waste drainage system is more often linked to chloride and ammonia. It is unclear what D’s criticism is exactly, but comments (1) and (2) appear to be correct statements of fact, and (3) is an opinion the SJE is entitled to state.

F3.4  Moisture Content Tests

46.  A more substantive complaint from D concerns the detected moisture levels in bathrooms of P’s unit. In short, there are two issues that the SJE was criticised for not having analysed properly.

47.  First, there is the issue of the location of the detected moisture.

48.  In short, John Yip considers that the microwave scan report by HKSL and his own moisture content test along the external wall support the possibility of seepage from the external wall. The relevant parts of John Yip’s Final Report at §7.2 read:

“According to the Infrared Thermographic Scanning and visual inspection to the external wall of the bathrooms of Flat l SF, apparent defects was found on the external wall around the floor level between the bathrooms of Flat 14F and I5F. Any defect on the external wall, including cracks, debonded tiles, would cause the possible path of weak point for the water penetration from exterior to interior. With prolonged and considerable amount of rainfall, water stains and high moisture content was noted at the corresponding location at the internal side of the external wall. The moisture was found spread to the adjacent floor slab, causing a larger” patch of water stain. Hong Kong Survey Limited report also supports the observation. According to their findings of microwave scanning to the ceiling of bathrooms of Flat 14B previously, it was noted that higher moisture concentrates near the external wall at the ceiling of master and guest bathroom of Flat l4F.”

49.  It is noted however that Nathan Lee’s Report does not discuss the issue of the location of the moisture, so I fail to see how adducing his report is supposed to help.

50.  In any case, it appears that the SJE has commented on this issue in noting that “the fall of the flooring (with the floor drain located at the external wall) may be the common cause of seeped water accumulating near the external wall.”[4] It is not explained in the SJE’s Report what “the fall of the flooring” means. Mr Leung submitted that this refers to the slant in the floor to channel water into the drain, which seems plausible but is not backed up by anything. In any case, this seems to be a small point which can again be dealt with by way of clarification.

51.  Second, and in my view more importantly, there is the issue of the timing of the detected moisture.

52.  In short, the results of the moisture content tests in Modern’s and C&L’s reports are noted by John Yip to vary across different weather conditions, which is said to be consistent with the Seepage being caused by rainfall, instead of pipes. The relevant parts of John Yip’s Final Report are §§7.6-7.7, which read:

“According to the inspection report from Modern Testing Consultants Ltd. "Section 7" and C&L Architects & Surveyors Limited "Section 6", the possibility of water seepage from the external wall should not be exempted. With the modern testing report findings, the readings of the moisture content on 21 April 2023 are relatively higher than on 11 May 2023. The weather conditions on these two days should be noted. The rainy condition was noted 48 hours before the test conducted in April but no rainy condition was noted 48 hours before the test conducted in May. For the reasons above, the potential source of water seepage at the external wall should not be exempted.

According to the varied moisture content record by Modern Testing Consultants Ltd. and C&L Architects & Surveyors Limited, the possibility of water seepage from the plumbing system should be exempted. The moisture content reading should be consistently high if water seepage from pipes has appeared. With the reasons above, the claim of water leakage from plumbing was not justified as Modern Testing Consultants Ltd. and C&L Architects & Surveyors Limited.”

53.  Although John Yip refers to the “[M]odern testing report findings” on 21 April 2023 and 11 May 2023, that seems to be an error, since Modern did not conduct moisture tests on those days. Modern’s moisture content tests were conducted on 26 September 2022 and 19 November 2022, and it was noted in respect of both dates that the weather was non-rainy and had been non-rainy for the past two days. It seems John Yip was referring to the C&L moisture content tests, which were conducted on 21 April and 11 May 2023. It is noted at §1.2 of C&L’s report that the weather was non-rainy on 21 April 2023 but rainy on the two days prior. The weather was non-rainy on 11 May 2023 and on the two days prior.

54.  This point on the timing of the moisture content by John Yip was noted and summarised in the SJE Supplemental Report at item 3 of the table at §9:

“John Yip commented on the Modern Report that "The rainy condition was noted 48 hours before the test conducted in April,

but no rainy condition was noted 48 hours before the test conducted in May. For the reasons above, the potential source of water seepage at the external wall should not be exempted."”

55.  The SJE’s comment here was simply to refer to his observations at item 2 of the table at §9 of the SJE Supplemental Report, which are noted at §38 of this Decision. Those comments primarily refer to the lack of a water spray test by John Yip. However, while the significance of a water spray test is obvious, concerns arise if the SJE disregarded other relevant evidence, even if such evidence is less conclusive than a water spray test. In this regard, it seems the timing of the detected moisture content – which appears to lend support to D’s argument that the external wall is the source – is a key piece of evidence that warranted comment from the SJE. The omission of a water spray test by John Yip does not, in itself, sufficiently address this issue.

56.  It also appears to me that this flaw in the SJE’s analysis goes beyond something which can be satisfactorily resolved by a clarification. This is because the SJE specifically noted this important point and purportedly answered it only by reference to the lack of a water spray test. Accordingly, it is not an issue which the SJE simply overlooked, but one which the SJE considered but gave an answer which was arguably no answer at all.

57.  Further, I agree with Mr Law that the fact that the SJE may be cross-examined on this matter is not an adequate solution. This is because for effective cross-examination, D would need an evidential basis to challenge the SJE’s conclusions. Additionally, more weight is likely to be given to the opinion of a court-appointed expert than the same points being put in counsel’s cross-examination of the SJE: see BY v GC [2025] EWFC 226 at §42(a).

58.  Given that the expert evidence pertains to a central and technical issue, I agree with Mr Law that requiring the parties to rely on a single expert carries the risk of effectively a trial by expert. After balancing all factors, I believe it serves the interests of justice for D to be permitted to present his own expert witness.

F4.  Complaint Category 3: Quantum

59.  This last complaint may be dealt with shortly, as it is plainly unsubstantiated. The criticism here appears to be that the SJE simply accepted the quantity of repair items on a quotation from PL Home Design to P dated 18 November 2023.

60.  The relevant part of the SJE Initial Report is at §26:

“Due to the time lapse, I am unable to conduct a site survey and measurements to verify the extent of the remedial works necessary to restore the Plaintiff’s premises caused by the water leakage. I, therefore, can only assume the quantity of the repair items on the quotation from PL Home Design dated 18 November 2023 is accurate. In this regard, I would offer my technical comments based on the quotation, considering whether the works were necessitated by the water leakage incident, as follows:”

61.  The SJE’s reasoning is entirely logical; he could only assume the quantity of the repair items. Indeed, Nathan Lee himself agreed that the “loss and damages assessment can only be conducted with reference to the information provided by [P] as renovation and repair work has already been carried out to [P’s unit]”.

G.  DISPOSITION

62.  For the reasons stated above, I agree with the Master that D should be granted leave to adduce a second expert report.

63.  At the hearing, I asked Mr Leung whether, if I were to dismiss the appeal and thereby permit D to instruct his own expert, P would likewise seek leave to adduce her own expert evidence. Mr Leung answered that P intends to deal with the present appeal first and take out a further application as necessary. I was therefore told that I could simply dismiss the appeal if I were to find in favour of D. Accordingly, I will dismiss the appeal.

64.  Although D has been overall successful in resisting the appeal, D presented an intricate case regarding multiple alleged problems with the SJE’s reports, which has mostly been unsuccessful except for the point concerning the timing of moisture content. This approach resulted in significant time and costs for both parties. Having regard to all the circumstances, I make a costs order nisi that P shall bear 50% of D’s costs arising from the appeal, with certificate for counsel.

65.  The above order nisi shall become absolute in the absence of application to vary within 14 days hereof.

66.  Unless any application for variation of the aforesaid costs order nisi is made within time, D shall lodge and serve his statement of costs on or before 14 April 2026. P shall lodge and serve her statement of objection by 21 April 2026. Summary assessment of the costs of the Application will be conducted on paper thereafter.