When a renovation needs a permit, when an architect is compulsory, what the heritage architect can block, which VAT rate applies, and which diagnostics and septic checks come with an old house.
Our guide to ruins and abandoned houses in rural France covers where to look, indivision between heirs and the headline restoration cost. This article looks at what happens after you have found a house with a clean title: which permission it needs, what the heritage architect can impose, what VAT and notary costs add, and which checks arrive with an old house. Some points are general rules we did not re-check against the official code, and we say so.
Permit or simple declaration
French planning law works by thresholds. According to construction-portal summaries consistent with each other, for an extension outside an urban zone of a local plan (PLU) up to 20 m² of floor area needs only a déclaration préalable (DP); above that a permis de construire (PC) is required, and the limit rises to 40 m² in an urban zone. Under 5 m² no formality is needed at the town hall, except in protected areas. The local plan can add stricter rules.
Renovation without extension is a different question. In general, work that changes the outside appearance (façade, windows, roof) goes through a DP, and a change of use, such as turning a barn into a house, needs more. Rebuilding a ruin whose walls are only partly standing is the hardest case: the authority may treat it as new construction, which can be refused in agricultural or natural zones of the PLU. We did not verify the exact rules for ruins, so ask the mairie for a certificat d'urbanisme on the specific plot before you commit, and put your planned works in the question.
When an architect is compulsory
An individual must use an architect when the total floor area after works exceeds 150 m², counting the existing house and the new part together. A 130 m² house extended by 25 m² reaches 155 m² and needs an architect even though the extension is small. The exemption is for individuals only: a company, including a family SCI, must use an architect for a building permit whatever the size. If you plan to buy through a company, take this into account.
The heritage architect (ABF)
If the house is within the protection perimeter of a listed monument, in a remarkable heritage site, or otherwise in a protected area, the architect of the Bâtiments de France (ABF) is consulted. By default the perimeter is 500 m and the ABF assesses whether the house and the monument are visible together. In these cases the opinion is often binding: the authority must follow it, and an unfavourable opinion blocks the permit. The ABF can require specific materials, window styles or roof pitches. The instruction time is extended by one month in these zones, and real delays can be longer. Ask the departmental architecture and heritage unit before you buy, and check the atlas of heritage areas.
Building cost and VAT
Our earlier figures remain the base: about EUR 1,500 to EUR 2,500 per m² for a full renovation of an old stone building, rising to EUR 2,000 to EUR 4,000 per m² when structural work is involved. VAT on works is reduced for a home completed more than two years ago and used as a main or secondary residence: 10% for improvement, transformation and maintenance works, and 5.5% for energy renovation. The works must be invoiced by a professional and must not enlarge the floor area by more than 10%; materials you buy yourself stay at 20%. Since 2025 the reduced rate must be stated on the quote and invoice. A heavily ruined building may not count as a home completed more than two years ago in the way the rules expect, so ask the contractor and the tax office before relying on 10%.
Aid: do not count on MaPrimeRénov'
Secondary residences are not eligible for MaPrimeRénov', according to secondary sources, and its status in 2026 is unclear in those sources (suspension, reopening and removal of some aid were all mentioned). Do not include it in your budget, and check France Rénov' for the current rules. The energy-savings certificate premium (CEE) was reported as open to secondary homes, and may be worth asking contractors about. The Denormandie scheme described in our earlier guide is for investors who then let the home.
Notary costs
In the old-property market the total notary costs run around 7% to 8% of the price in departments at the standard rate, and 7.5% to 8.5% where the department raised the transfer duty to its higher level (the rise is allowed for deeds between 1 April 2025 and 31 March 2028). The notary's own fee is a small share, roughly 0.8% to 1.3%; most of the total is taxes. The list of departments with the higher rate differs between sources, so ask the notary for the exact figure for the house. On a very cheap house the fixed items weigh more in percentage terms, so budget by the notary's written statement, not by a percentage.
Diagnostics and the septic tank
The seller supplies the technical diagnostics file. In summary of popular guides: a lead exposure report applies to homes built before 1949; asbestos applies where the building permit dates from before 1 July 1997; termite reports depend on a prefectoral zone and are valid for 6 months; electricity and gas checks apply to installations older than 15 years; the energy performance certificate (DPE) is valid for 10 years, with an energy audit for classes E, F and G. For a home without mains drainage, the report of the non-collective sanitation service (SPANC) must be under three years old. If the system is not compliant, the buyer has one year after the deed to bring it up to standard, and the cost can be negotiated into the price. Whether a roofless ruin is exempt from some of these items is not clear, so confirm the scope with the notary.
Order of operations
- Ask the mairie for a certificat d'urbanisme and check the PLU zone and any ABF perimeter.
- Confirm clean title (no indivision problem) with the notary.
- Get a SPANC report, the diagnostics and a structural survey.
- Decide whether you buy as an individual or through a company, given the architect rule.
- Obtain written quotes stating the VAT rate; see also mortgages for foreigners in France, property prices and buying costs and investment risks.
FAQ
Do I need a permit to repair a roof? If it changes the appearance of the building it usually goes through a DP, and in an ABF zone it needs the heritage architect's opinion; ask the mairie. Is an architect always required? No, only when the floor area after works exceeds 150 m² for an individual, and always for a company applying for a permit. Can I get MaPrimeRénov' for a second home? According to the sources we found, no; check the current scheme. Is the septic tank my problem as a buyer? If it is non-compliant, you generally have one year after the deed to fix it, so price it in.
How we help
We help you ask the right questions of the mairie and the notary, connect you with independent local professionals and compare quotes in your language. This guide is informational only and not legal, tax or construction advice; verify the current rules before you commit.