1. All of the plaintiffs' claims are dismissed.

2. The costs of lawsuit are assessed against the plaintiffs.

1. Details of disposition;

A. 1) The Plaintiff Co., Ltd. is a construction technology service provider that conducts a comprehensive supervision business (hereinafter “Co., Ltd.”). 2) The Plaintiff Co., Ltd. was awarded a contract from the Defendant for construction management services from the Defendant (hereinafter “instant apartment building”, “instant construction project”) on the construction phase supervision of C apartment construction (from January 23, 2017 to September 21, 2019), and performed construction management services (from January 23, 2017 to September 21, 2019). The Plaintiff Co., Ltd. took overall charge of the construction project management services of the instant construction project as a construction project manager affiliated with the Plaintiff Co., Ltd.

B. The Board of Audit and Inspection (1) conducted an audit on the operation of the noise reduction system between floors) conducted by the Defendant, etc. from September 3, 2018 to January 18, 2019, the Board of Audit and Inspection conducted an audit on the operation status of the noise reduction system between apartment floors, such as prior recognition of the noise soundproof structure of apartment houses, construction, performance assessment, etc.

2) As a result of the inspection conducted by the Board of Audit and Inspection of the noise-preventive performance of the sample generation prior to the execution on the 89 site where the sample generation among the 115 construction sites implemented by the Defendant was located, it was confirmed that the noise performance was measured after the 31 construction sites including the instant construction sites, which did not measure the performance of the sample generation noise or 2 to 382 days after the commencement of the construction works.

3) In addition, as a result of the inspection conducted after the Board of Audit and Inspection confirmed whether buffer materials brought into the field for 99 sites meet the quality standards, the construction was commenced before the issuance of a buffer quality inspection report from the 57 construction sites (58%) including the instant construction site. In particular, the Defendant’s 55 sites were confirmed to have commenced the construction before requesting the quality inspection of buffer materials.

4) Of the production companies that supplied buffer materials to the Defendant 42 sites, the quality of buffer materials is appropriate by selecting three sites supplied by the top three companies in the order of construction.