When Centimetres Decide Millions: The Amendment to Article 5a of the Development Act and the Growing Risks for Developers.

As of 13 February 2026, the amended Article 5a of the Development Act may become one of the key provisions in disputes between purchasers and developers.

The statutory linkage provided for in this provision, whereby the price of a unit is tied exclusively to its usable floor area – determined in accordance with the relevant PN-ISO 9836 standard – significantly limits contractual freedom with respect to the calculation of floor space, while the application of the standard alone leads to an increase in the formal area of the unit in contradiction to the arrangements previously functioning on the market.

In practice, this means that any overstatement of the area affecting the price may give rise to a claim for reimbursement of the unduly collected part of the consideration together with interest.

Disputes concerning usable floor area currently constitute one of the greatest litigation risks in the development sector. Every developer should be aware that appropriate argumentation already at the contract stage may protect them against costly refunds for “missing” square meters.

The existing sales models, in which the area used for settlement included, inter alia, space beneath partition walls, may become subject to judicial review. Combined with the interpretative position of the UOKiK, the risk of disputes increases with respect to the correctness of price determination, compliance of agreements with mandatory provisions of law, and potential infringement of collective consumer interests.

From a litigation perspective, it will be crucial to determine whether the usable floor area was incorrectly defined, whether this had a direct impact on the amount of the consideration, and whether the claim should be classified as unjust enrichment, contractual liability, or a consequence of the application of unfair contractual terms. This amendment, interpreted literally, diverges from the previous position of the development industry – confirmed by the UOKiK – which interprets the issue systemically and tends to calculate the area of a unit including the area of partition walls, provided they are removable.

This polarisation of interpretative views constitutes a flashpoint for a new phase of court disputes on the real estate market – precision in measuring floor area, and consequently the total price of the unit, will now be under scrutiny by the legal services market offering the prospect of “easy” recovery of amounts paid by consumers. The argumentation in these disputes will, of course, depend on the party, each of them using, for its own purposes, the interpretation favourable to it. In a broader perspective, we are facing significant volatility and legal risks in this area – until a consistent line of case law is established, the market will struggle with instability in the approach to calculating unit prices, numerous civil disputes, and likely divergent judicial positions.