Lex Weber: what you can still buy, sell and extend

In two sentences: the Lex Weber caps second homes at 20% of each commune and bars any new ones where that ceiling is passed — 331 communes as of 31 March 2026. But homes that already existed on 11 March 2012 escape the ban, and since 1 October 2024 they may be extended by 30%.

Two Swiss laws are routinely confused. The Lex Koller governs who may buy: it looks at your nationality and where you live. The Lex Weber takes no interest in who you are — it governs what may be built, and where. A Swiss national living in Geneva is bound by it exactly as a British buyer is. Both may apply to the same purchase, or neither.

What the constitutional article actually says

The text is deceptively short. Article 75b of the Federal Constitution, approved by popular vote on 11 March 2012 and in force the same day, reads: “Second homes shall constitute no more than 20% of the total stock of residential units and of the gross floor area used for residential purposes in each commune.”

Two details are usually missed. The cap applies to two measures — the number of dwellings and the habitable floor area — and it is assessed commune by commune, not by canton or by resort area. One village can be frozen while its neighbour is not.

The implementing act, and the 331 communes

The constitutional article needed the Federal Act on Second Homes of 20 March 2015, in force since 1 January 2016, to become operative. Article 6 sets the rule: in a commune above 20%, no new second home may be authorised. And where the share is still below 20% but a permit would push it over, that permit cannot be granted either.

Every Swiss commune must compile a housing inventory once a year. As of 31 March 2026, the Federal Office for Spatial Development counted 331 communes above 20%, mostly in the Alps — down from 337 a year earlier. Nine crossed the threshold upwards, three fell back below. A commune that fails to file its inventory on time is deemed to exceed 20%: the omission is expensive.

So before any transaction, the only question that matters is whether that specific commune is on the list. The Federal Office publishes an interactive map. From 2027 it will calculate the share directly from the Federal Register of Buildings and Dwellings, which will simplify the procedure.

The decisive point: dwellings created under the former law

This is the article nobody quotes, and it explains why the resort market did not die in 2012. Article 10 defines a dwelling created under the former law: one that lawfully existed before 11 March 2012, or held a final building permit on that date.

Article 11 paragraph 1 is unequivocal: for such dwellings, the manner of occupation is unrestricted. You may live in them year-round, let them, use them for a few weeks each season, or sell them to a buyer who will set foot there only in February. No federal use restriction attaches. It is precisely this stock of pre-2012 property that makes up most of what changes hands today in Verbier, Crans-Montana and Gstaad.

They may also be renovated, converted, and even demolished and rebuilt without a use restriction being imposed.

The 1 October 2024 easing: the 30% rule

This is the change many owners have yet to register. The amendment of 15 March 2024, in force since 1 October 2024, rewrote article 11. Within building zones, the main usable floor area of a dwelling created under the former law may now be increased by up to 30% of what existed on 11 March 2012. And within that limit, “additional dwellings and buildings may be created”.

Read that last clause carefully: this is not merely permission to enlarge a room. Within the 30%, additional dwellings may be created, free of use restriction. On a generously sized older chalet, that changes what the plot is worth — and it is worth establishing the 11 March 2012 reference area before setting a price.

Beyond 30%, extension remains possible, but the dwelling must then be declared a primary residence or tourist accommodation, with the restriction entered in the land register. At that point you are in a different regime altogether.

What can still be built from new

In a commune above 20%, a new dwelling is authorised on only two conditions (article 7): it must be used as a primary residence — or an equivalent — or as tourist accommodation. That second route is narrower than it sounds: the dwelling must be made durably available to guests for short stays on market terms, and must either sit in the building where the owner has their main home, or not be fitted out to the owner’s personal requirements and be marketed through an organised accommodation business.

Article 8 opens a further door, for hotels: an organised accommodation business may create dwellings without use restriction if the proceeds are necessary to its viability and reinvested in the establishment, and if their floor area does not exceed 20% of the total area of rooms and dwellings. This is the mechanism behind most new-build schemes attached to a hotel in the resorts.

Cantons may be stricter — and are

A common error is to assume federal law has the last word. Article 3 paragraph 2 expressly allows cantons to “restrict the construction and use of dwellings more than this Act does”. Article 12 further requires them to act against abuse, notably by controlling the conversion of a primary residence into a second home.

In practice, a dwelling can be unrestricted under federal law and constrained by a communal regulation. Before buying in a resort, the check has to cover all three layers: the federal Act, cantonal law, and the commune’s own rules.

What this means when you buy or sell

For a seller, the question to settle before price is ever discussed is the date: did the dwelling lawfully exist before 11 March 2012? If so, it sells free of use restriction, and its 30% extension potential forms part of its value — it deserves to be documented, not left for the buyer to discover.

For a foreign buyer, the two laws stack: the Lex Weber decides what the property can become, the Lex Koller decides whether you may acquire it at all. A property entirely compliant with one can be closed off by the other.

This is a market where discretion is the norm: in Verbier, Crans-Montana and Gstaad, the most sought-after pre-2012 properties rarely change hands through a public listing. Our pages on Verbier, Crans-Montana and Gstaad set out how we work there, and a confidential valuation can be prepared without your property appearing anywhere.

This article is an information summary, not legal advice. For a specific situation — extension potential, change of use, a project inside a building zone — consult a lawyer, the commune concerned or the competent cantonal office. Sources: art. 75b of the Federal Constitution (SR 101) and the Federal Act on Second Homes of 20 March 2015 (SR 702, as at 1 October 2024) on Fedlex; amendment of 15 March 2024 (AS 2024 501); Federal Office for Spatial Development press release of 31 March 2026. A French version of this guide is available: Lex Weber, résidences secondaires.