A. On November 21, 2017, the Plaintiff, a corporation established for the purpose of construction business, etc., entered into a construction contract with the Defendant on the construction work that newly constructs neighborhood living facilities on the ground of Echeon-si (hereinafter “instant construction work”) with the Defendant, setting the construction cost of KRW 700,00,000 (excluding value-added tax) and the construction period of the construction from November 21, 2017 to April 30, 2018 (hereinafter “instant construction contract”). The instant construction work was undertaken around that time.

B. During the construction process of the instant construction, the Defendant requested the Plaintiff to change the said neighborhood living facilities to the exhibition hall, and the Plaintiff continued to construct the exhibition hall (hereinafter “instant building”) in accordance with the changed design drawings from March 24, 2018.

C. Since then, inasmuch as there was no agreement on the amount of additional construction costs, etc. due to the design modification while only the reinforced concrete construction of the instant building was underway, the Plaintiff agreed with the Defendant to rescind the instant construction contract as of June 18, 2018, and at that time, delivered the instant building to the Defendant, and agreed to settle the construction cost according to the outcome of appraisal in the instant lawsuit (hereinafter “instant settlement agreement”).

The Plaintiff was paid KRW 375,000,000 as construction price according to the instant construction contract.

E. Until the time when the instant contract for construction work was rescinded, the appraiser calculated the construction cost as KRW 458,220,626 for the part that the Plaintiff executed and ordered.

On the other hand, in the building of this case, the defects of rupture, water leakage, material separation, and steel rupture in the concrete structure exist, and the defect of the heatation phenomenon of floor slab concrete, and the defect of the shock of external heat rupture are applied to the building of this case, and the cost accounting ratio of the Public Procurement Service in 2018 is applied.