Hello, this is Attorney Bae Ki-hyung of Cheongchul Law Firm.

Once construction of a new apartment complex is completed and residents begin moving in, the most commonly discovered and most frequently disputed defect is 'cracks' in the concrete exterior or interior walls. Given the nature of concrete as a material, a certain degree of fine cracking is inevitable, and contractors often refuse repairs by arguing that "thin cracks under 0.3mm fall within the legally permitted 'allowable crack width' and therefore are not defects."

The council of occupants' representatives, on the other hand, counters that "no matter how fine, such cracks are not only unsightly but may later lead to water leakage or structural problems," and a fierce legal battle unfolds over hundreds of millions of won in exterior painting and defect repair costs.

Today, I will explain whether hairline cracks below the so-called 'allowable crack width (0.3mm)' can be recognized as apartment defects so that repair costs may be claimed, along with recent court precedents and clear standards on this issue.

Whether Hairline Cracks Under 0.3mm Constitute Defects – The Courts' Firm and Consistent Position

[Question] The contractor refuses to repair cracks on the grounds that they are below the 'allowable crack width' of 0.3mm under construction standards. Can such fine cracks legally constitute apartment defects?

[Answer] In short, absent special circumstances, Korean courts firmly and consistently recognize hairline cracks under 0.3mm as defects and affirm the contractor's liability for damages (defect repair).

Of course, the contractor's argument has some basis. Under the Concrete Structure Design Code (콘크리트구조기준) established by the Ministry of Land, Infrastructure and Transport, an 'allowable crack width' is set within a range that poses no significant problem for structural stability or durability, given the characteristics of concrete as a material. Typically, the allowable crack width is around 0.3mm in wet environments (such as general outdoor areas) and 0.4mm in dry environments (such as indoor areas). In addition, the Ministry's 'Standards for Defect Investigation, Repair Cost Calculation, and Defect Determination in Multi-Family Housing' (공동주택 하자의 조사, 보수비용 산정 방법 및 하자판정 기준) provides, in principle, that exterior wall cracks are determined to be defects when they reach 0.3mm or more, the allowable crack width for concrete.

However, the courts focus far more on substantive relief for residents and the durability of the building than on administrative standards.

Numerous precedents, including Supreme Court Decision 2007Da83908 rendered on February 26, 2009, have expressly rejected the contractor's argument that "cracks of 0.3mm or less are permitted cracks and therefore cannot be defects," and affirmed the lower court's ruling recognizing cracks below the allowable crack width as defects.

The specific reasons the courts recognize cracks under 0.3mm as defects are as follows.

1. Crack Propagation and Reduced Durability Over Time

No matter how fine a crack may be, if left unattended, rainwater and carbon dioxide will penetrate over time. This causes the internal rebar to corrode, and the crack eventually spreads, creating a risk of seriously reducing the durability of the structure.

2. Aesthetic Impairment and Substantive Defects

Cracks in exterior or interior walls are unsightly in themselves, causing inconvenience to residents' daily lives and adversely affecting the property value of the apartment. This is regarded as a defect lacking 'the quality a building should ordinarily possess under common transactional standards.'

3. The Proviso in the Ministry of Land, Infrastructure and Transport Standards

The 'Standards for Defect Investigation, Repair Cost Calculation, and Defect Determination in Multi-Family Housing' that contractors rely on also contains a proviso. Specifically, it provides that "even cracks below the allowable crack width are determined to be defects where there is water leakage or where they are found at locations where rebar is placed," making it clear that hairline cracks are not automatically exempt from liability.

Have Hairline Cracks Included in the Appraisal Report and Secure Painting Costs as Well

From the standpoint of the council of occupants' representatives (plaintiff), when the contractor defends by invoking the allowable crack width, it is of primary importance during the court-appointed appraisal to actively argue that even cracks under 0.3mm are in a condition requiring repair and pose significant risks of leakage or aesthetic impairment, so that they are included as defects in the appraisal report. Furthermore, the key strategy for maximizing damages is to secure full recognition not only of the crack repair itself but also of the 'painting (paint) costs' that necessarily follow crack repair.

Conversely, from the standpoint of the contractor (defendant), the defense strategy should be to prove that the hairline cracks are not the result of faulty construction but a natural aging phenomenon caused by the inherent drying shrinkage of concrete or the residents' neglect of maintenance, or to reasonably limit the scope of repair for cracks under 0.3mm (e.g., partial painting rather than full repainting) in order to reduce the amount of damages.

Disputes over hairline cracks in apartments are a core issue where the amount of damages can differ by hundreds of millions of won or more depending on the appraisal method and scope of repair, so specific legal review and meticulous appraisal response are needed from the early stages of litigation.

Cheongchul Law Firm, drawing on its deep understanding of large-scale multi-family housing defect disputes and construction appraisal practice, provides optimal solutions to prevent unjust reductions in defect repair claims and protect the legitimate rights of residents. If you are facing difficulties with apartment crack defects and repair cost issues, please consult with the experts at Cheongchul Law Firm.

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Attorney Bae Ki-hyung has worked at the Defense Installations Agency and in the construction/real estate team of a major law firm, providing legal advice on the entire process of government contracts and construction projects, including large-scale construction works such as public works, defense facility projects, and SOC construction projects, and has extensive experience and expertise in resolving related litigation. If you need assistance with public works, private construction projects, public procurement contracts, state property, local government property, or public property, please feel free to contact us at any time.

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Cheongchul Law Firm is composed exclusively of attorneys from Korea's top five major law firms, the prosecution, and in-house legal teams of large corporations, and responds to each case not with a single attorney but with a team of specialized attorneys in the relevant field. Going beyond resolving specific issues, Cheongchul provides comprehensive solutions for your overall business, offering legal consulting focused on ultimately achieving what our clients want. If you need help achieving your goals, please do not hesitate to contact Cheongchul.