Facts
Parties and instances: The non-profit housing cooperative (plaintiff and appellant) commissioned [B. AG] (defendant 1, now in liquidation) to carry out floor and wall coverings in the area of the balconies and wet rooms in connection with replacement new buildings. [E. AG] (defendant 2, site management/planning) and [F. AG] (defendant 3) were entrusted with planning and site management. The plaintiff asserted systematically defective work by defendant 1, which had allegedly led to visually detectable moisture damage (secondary defects), and accused defendant 2 of breaching its duties of execution supervision and disclosure; defendant 3 was to be jointly and severally liable.
Expert opinions and findings: The specialist expert [G.] was commissioned on 22 November 2013 and produced four expert reports (examination of defects in individual apartments; inventory of defects dated 29 December 2014; responsibility of site management dated 29 June 2015; summary dated 21 September 2018). On 13 July 2016 an official inspection with test drilling took place. [H. AG] rehabilitated all 132 balconies and 63 wet rooms essentially in summer 2016, after having documented their condition photographically. On 19 August 2014 a meeting took place, in whose minutes the defects in the examined objects were acknowledged, further random checks were reserved, and a reservation regarding the insurers' own experts of defendants 1 and 2 was recorded.
Lower court: The action of 11 December 2017 for replacement costs of CHF 2,451,993.40 and consequential damage of CHF 214,975.45 (each incl. VAT, plus interest) was dismissed with costs by the Commercial Court of the Canton of Zurich by judgment of 6 August 2020. The plaintiff had not sufficiently pleaded or proven the claims and their factual basis. The third-party notice to defendant 1 was noted.
Proceedings before the Federal Supreme Court: The plaintiff requested annulment and remittal, alternatively approval of the action. Suspensive effect was granted with respect to the party compensation of CHF 71,000.-- owed to defendant 1, over which bankruptcy proceedings had been opened on 18 August 2020; the proceedings were stayed pursuant to Art. 207 DEBA. Assignee creditors ([C. AG] and [D.] ) joined the proceedings; [I. GmbH] waived its participation.
Considerations
Standard of review: The Federal Supreme Court applies the law of its own motion (Art. 106 para. 1 FSCA), but in principle examines only the complaints raised, having regard to the requirements of reasoning (Art. 42 paras. 1 and 2 FSCA). For complaints concerning fundamental rights, cantonal and intercantonal law, the qualified duty to raise complaints applies (Art. 106 para. 2 FSCA). The establishment of facts may only be corrected in cases of arbitrariness (Art. 105 para. 2 FSCA); arbitrariness exists only where the finding is manifestly untenable. Respondents 2 and 3 may, in their response to the appeal, challenge considerations that are unfavourable to them (Art. 76 para. 1 FSCA); a mere request for remittal suffices, and the alternative request for approval makes the request sufficiently clear.
Requirements of substantiation: Under Art. 55 para. 1 CPC, and subject to the principle of party presentation, the legally relevant facts must be set out and the evidence specified. A conclusive assertion suffices in its essential features; only where the opposing party disputes it is more detailed substantiation of individual facts required. Denials must be so specific that it is recognisable which assertions are disputed (Art. 222 para. 2 CPC). Where specialist knowledge is lacking or there is an information asymmetry, the requirements are relaxed. As regards damage: the claimant must set out which costs were incurred for which works; a breakdown by individual defects understood in legal terms is not required, and the court may estimate the proportion attributable to the defects found, at its discretion (Art. 42 para. 2 CO by analogy, discretion).
Excessively strict requirements of the lower court: The lower court partly imposed excessively strict requirements of substantiation, in particular by demanding a remediation concept and by anticipating the outcome of the evidence; to that extent the appellant rightly complained. This does not suffice, however, since the appeal succeeds in result only if the decision is relevant; otherwise there is merely a dispute over the reasons of the decision, for which no legal interest in protection exists (Art. 76 para. 1 lit. b FSCA).
Binding nature of the expert opinions: The expert opinions of the specialist expert are not binding. The minutes of the meeting of 19 August 2014 reveal only an acknowledgment of the balconies and wet rooms examined; further investigations and the reservation regarding the insurers' own experts speak against any binding effect. Agreement that the expert should continue his mandate does not establish binding effect. An arbitral-type expert determination under Art. 189 CPC was not asserted; mere unopposed acquiescence or oral acknowledgment is insufficient. The appellant did not adequately set out which specific facts had been acknowledged.
Court expert after remediation: The appellant had the defects remediated before the court expert was appointed. A court expert must be able to review the private expert opinions independently; to that end the appellant would have had to set out how, after the remediation, a review of the defectiveness and causation, in particular the exclusion of alternative causes, could be carried out with a certain degree of probability. An impermissible search for evidence or a 'fishing expedition' is excluded. The photographic documentation and the official inspection do not sufficiently enable this; witness testimony from the persons entrusted with the remediation lacks independence. Urgency that would have made preservation of evidence impossible does not exist, since considerable time elapsed between the mandate, the meeting and the official inspection.
Right to rectification and forfeiture: The appellant had requested defendant 1 by letter of 27 May 2015 to rectify the defects; defendant 1 confirmed the rectification on 5 June 2015. According to the appellant's account, a two-stage procedure was to apply, with the scheduling to be communicated after the written commitment. This scheduling was not communicated; according to the letter of 30 October 2015, defendant 1 was to hold itself ready. A delay on the part of defendant 1 was caused by the appellant itself, so that no forfeiture of the…