France's Mountain Law: buying a chalet or a plot

Where does the Mountain Law apply?

The communes concerned were designated by nine interministerial orders issued between February 1974 and September 1985. For the orders of 1982 to 1985, only the communes in annex I are subject to the planning rules. The ministry warns that these lists are not fully up to date, owing to mergers and splits of communes, and that an updated list will be published. Some communes fall under both the Mountain Law and the loi Littoral (Coastal Law): those bordering a lake of more than 1,000 hectares or located by the sea.

The mountain zone is defined by natural handicaps: altitude resulting in a shorter growing season, steep slopes preventing mechanisation, or a combination of the two (Mountain Law, art. 3). Each zone belongs to one of six ranges: the Alps, Corsica, the Massif Central, the Jura, the Pyrenees, the Vosges. In the overseas départements, the Act provides for specific requirements, an option that “has not been used to date” (DGALN sheet no. 1).

The planning rules are in articles L122-1 to L122-27 and R122-1 to R122-20 of the Planning Code.

The principle: building must adjoin existing settlements

To prevent scattered building, development must adjoin what already exists (art. L122-5). Since the Montagne II Act, article L122-5-1 specifies that adjoining is assessed according to the local characteristics of traditional housing, the buildings in place and the existence of roads and utility networks. DGALN sheet no. 2 (June 2026) considers in particular:

• the distances between buildings, proximity of a few metres not being necessary;
• the density, form and logic of local development;
• architectural, landscape and topographical features;
• the presence of roads and utility networks, whose mere existence does not amount to development.

Each case is assessed using maps, photos or even a site visit. In a mountain commune with no PLU (local development plan) or carte communale (simplified municipal map), it is this adjoining rule that applies, and not the restriction of building to built-up areas under the règlement national d’urbanisme (national planning regulations) (Conseil d’État, the highest administrative court, 16 April 2012, cited by sheet no. 2).

Exceptions useful to a buyer

The Act provides for eight exceptions, interpreted strictly. The most common ones for a private individual mainly concern existing buildings not adjoining a settlement; the last row covers tourist developments (sheet no. 2):

What this means: an isolated house can often be renovated and enlarged to a limited extent, but a bare plot away from hamlets is in principle unbuildable, even if a road serves it.

Lakes and alpine chalets: two separate regimes

Lake shores. The natural parts of the shores of natural or artificial bodies of water of less than 1,000 hectares are protected over 300 metres from the shore: buildings, installations, new roads, extraction and excavation are prohibited there, subject to the exceptions in article L122-13. The protection applies to the whole body of water, even if only some of the communes bordering it are in the mountain zone (DGALN sheet no. 4). For the ten mountain lakes of more than 1,000 hectares, including Annecy, Le Bourget, Lake Geneva (le Léman) and Serre-Ponçon, the communes bordering them are subject to both the Mountain Law and the Coastal Law; where they diverge, the stricter rule applies, “frequently” that of the Coastal Law (DGALN sheet no. 4).

Alpine chalets and summer pasture buildings. Their restoration, reconstruction or limited extension may be authorised “with the aim of protecting and enhancing mountain heritage” (art. L122-11, 3°). This prefectoral authorisation, given after consulting two département commissions, is not a building permit, and vice versa. Where the chalet is not served by a road, or is served by one that is unusable in winter, a servitude (easement) restricting winter use must first be established. Sheet no. 10 notes that these restorations are frequently used to create second homes, which the text does not prohibit.

Second homes in ski resorts: what can restrict a purchase

Since 21 November 2024 (Act of 19 November 2024), a commune may designate areas in its PLU where any new housing is reserved for main residences, where second homes exceed 20% of housing or in a zone tendue (high-demand area) (ANIL, the national housing information agency). This easement must appear expressly in the promesse (preliminary contract) or the deed of sale, failing which they are void. If the property is occupied in breach of it, the mayor may impose a daily penalty of €1,000 per day, up to €100,000. Only holiday letting of your main residence remains allowed, for 120 days a year at most.

Which professional to consult

The géomètre-expert (chartered surveyor) measures the distance from a plot to existing buildings or to a lake shore. The notaire (notary) checks for a main-residence easement or a restriction on winter use. The agent immobilier (estate agent) can check, before the viewing, whether the property is in an area reserved for main residences, and the courtier en crédit (mortgage broker) can cost the financing of a second home.