Construction tolerances and the Salva casa decree: what to check before selling

During a check, differences may emerge between the measurements of the home and those of the project. To understand how to treat them, the documents, the period of the works and the applicable conditions need to be examined. The law distinguishes small differences, which are not violations, from those that must be regularised; the boundary matters because, when selling, a surveyor must be able to certify the lawful status of the home.

The basic rule

A deviation from the measurements in the building permit (height, distances, volume, covered area) is not a planning violation if it stays within 2% (Article 34-bis(1) of Presidential Decree 380/2001).

The 2024 thresholds

The 2024 “Salva casa” decree added wider thresholds for works carried out by 24 May 2024, which increase the smaller the home: 2% above 500 m² of usable floor area, 3% between 300 and 500, 4% between 100 and 300, 5% under 100 m², 6% under 60. For works after 24 May 2024 only 2% applies. The thresholds are calculated on the floor area authorised by the permit.

Lawful status

The same reform clarified how the lawful status of a home is reconstructed: what counts is the permit that provided for its construction, or the one for the last works on the whole property, together with later permits (Article 9-bis of Presidential Decree 380/2001).

Why it matters when selling

For buildings started after 17 March 1985 the deed must state the details of the building permit, otherwise it is void (Article 46 of Presidential Decree 380/2001). A difference within the tolerances does not require an amnesty, but it must be declared by a surveyor in a statement attached to the deed of transfer (Article 34-bis(3)); one beyond the thresholds does, and the municipality’s timescales must be built into the sale calendar. The check is done by a surveyor, on the municipality’s documents, before the preliminary contract.