Unauthorised building works (abuso edilizio): what they are and how to spot them
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What unauthorised building works are, in plain termsHow unauthorised building works are discoveredHow big can the difference be without it being unauthorised?What happens if you buy a property with unauthorised worksExample with numbersIn practiceFrequently asked questionsSourcesUnauthorised building works (abuso edilizio) are work carried out on a property without the building permit required by law, or in a way different from what that permit authorised. They are usually discovered by comparing official documents with the actual condition of the house.
What unauthorised building works are, in plain terms
The building permit (titolo edilizio) is the authorisation or notification that the Comune receives before building or changing a property. The rules are in the Consolidated Building Code (Testo unico dell'edilizia), Presidential Decree 380 of 2001, which you can read on Normattiva.
The law provides for several types of permit: free building work (edilizia libera, art. 6), the CILA (art. 6-bis), the SCIA (art. 22) and the building permit (permesso di costruire, art. 10). Which one is needed depends on the type of work. You can find the differences between these permits explained in CILA, SCIA, building permit: the differences.
There are two forms of unauthorised building works. The first is work carried out with no permit at all, for example adding a room to the house without having submitted anything. The second is work carried out under a permit, but differing from how it was actually built, for example a window moved or a room larger than the approved plan.
Not every change is unauthorised. Some minor works fall under free building work, and some small differences in measurements are tolerated by law. We cover these further on.
How unauthorised building works are discovered
There is no single check that tells you everything. Usually the problem emerges by cross-checking several documents. These are the ones to check:
- the land registry extract (visura catastale), which shows the property's details as recorded in the Land Registry (Catasto); you can request it online through the service of the Agenzia delle Entrate;
- the cadastral floor plan (planimetria catastale), to be compared with the actual house: rooms, windows, walls, mezzanines;
- the Comune's building permits, which you can request through right of access to documents (accesso agli atti); this guide explains how;
- the appraisal report (perizia), if the property is being auctioned: it must state whether the property is compliant from a building point of view and how much it would cost to regularise it.
The most important check is carried out by the notary. In deeds between private parties, the law requires the building permit to be stated. If it is missing, the deed is void (art. 46, para. 1, of the Consolidated Building Code). Cadastral compliance must also be declared in the notarial deed (rogito), on pain of nullity (art. 29 of Law 52 of 1985).
Warning signs to take seriously in an advert or during a viewing: a floor plan that does not match the house, rooms or mezzanines not shown, cadastral details different from those in the deed, recent works without documents. Always ask the seller for written explanations.
How big can the difference be without it being unauthorised?
The law tolerates small deviations from the measurements in the permit. Article 34-bis of the Consolidated Building Code refers to a tolerance of 2% on measurements. With the Salva casa decree, the tolerances for smaller units have been widened, but the precise figure must be checked in the law itself, not based on hearsay. Tolerances are not unauthorised works and do not need to be regularised. You can read more in Construction tolerances: what is not unauthorised (Salva casa).
Invented example. The approved plan provides for a room of 20 square metres. The one built measures 21. - Difference: 1 square metre. - As a percentage: 1 out of 20, that is 5%. - The 5% exceeds the base 2% set by article 34-bis: it falls within the tolerance only if the higher percentages introduced by Salva casa apply to the unit (from 2% to 5% depending on the surface area), to be verified with the technician.
If the difference had been 0.4 square metres, that is 2%, you would have remained within the 2% base threshold. The calculation is done by the technician, but you can redo it yourself using the measurements from the floor plan and the plan.
What happens if you buy a property with unauthorised works
If the unauthorised works can be regularised, the owner can apply for regularisation (sanatoria). Double conformity is required: the work must comply both with the rules in force when it was carried out and with those in force when regularisation is requested. The mechanism is explained in Double conformity: what it means and in Building regularisation: how it works.
The law also provides a procedure for partial discrepancies and essential variations, introduced by the Salva casa decree (Decree-Law 69 of 2024). Here too, conformity is required, subject to conditions and a payment.
If the unauthorised works cannot be regularised, the buyer must remove them at their own expense. The cost of this work weighs on the real price of the property, which is why it must be checked before buying.
In court auctions the rules are partly different. The appraiser must state the costs and methods of regularisation. The successful bidder, if regularisation is possible, must submit the application within 120 days of notification of the transfer decree (art. 46, para. 5, of the Consolidated Building Code). The transfer decree (decreto di trasferimento) is the measure by which the judge transfers ownership to you after payment of the price.
Example with numbers
Let's take an invented case. You buy a house for €100,000. The appraiser reports a veranda built without a permit, which can be regularised, with estimated regularisation costs of €4,000. - Purchase price: €100,000. - Regularisation costs: €4,000. - Real total cost: €104,000.
The figure is invented, but the method is the real one: you add the cost of regularisation to the price before deciding whether to bid.
In practice
- Request the land registry extract and the floor plan, and compare them with the actual house.
- Request the Comune's building permits through right of access to documents.
- Ask the notary to verify the building permit before the deed is signed.
- If you are buying at auction, read the section on building compliance and regularisation costs in the appraisal report.
Frequently asked questions
Does an unauthorised building work block the sale?
Not always. Unauthorised works that can be regularised can be dealt with, but this must be done before or after the deed according to the rules of the case. Works that cannot be regularised reduce the real value of the house and must be taken into account in the price.
Who pays for regularisation, the seller or the buyer?
It depends on what the contract says. This point should be clarified in writing in the offer or in the preliminary contract (compromesso), before signing.
Do unauthorised building works become time-barred?
The mere passing of time does not make them compliant. The matter should be checked with the technician and the notary, because the rules change over time.
Sources
In the same chapter
- Unauthorised building works: when they become time-barred and what a buyer risksUnauthorised building works do not become legal over the years. If you buy, the risk is inheriting them: here is what to check in the appraisal report and at the Comune.
- Building amnesty: the 1985, 1994 and 2003 lawsAn unfinished building amnesty from 1985, 1994 or 2003 does not make the property safe: here is what to check at the Comune before you buy.
General information, not legal or tax advice: the law and the notice of sale prevail.
