Opening a
load-bearing wall.

A load-bearing wall carries part of the weight of the building: floors, walls of the upper storeys, sometimes the roof structure. Removing it or cutting through it without compensating means shifting those loads onto elements that were not designed to take them. Façade walls are almost always load-bearing, as are cross walls, the interior walls that divide the building and on which the joists or beams of the floors rest.

Several clues guide the diagnosis: a wall clearly thicker than the partitions, a wall that continues identically from one storey to the next, a wall placed under a beam or perpendicular to the joists. The original plans, when they exist, give a first answer. But no clue replaces an on-site investigation: in old houses, successive alterations often blur the picture, and an apparently light partition may have been loaded over the course of works.

In a co-ownership building, the question is also a legal one: load-bearing walls are part of the structural work, which the co-ownership rules generally classify among the common parts, even when they run through your flat.

The structural study is the cornerstone of the project. It starts with a load path calculation: what the wall actually carries, storey by storey. From this it determines the beam to be fitted above the opening, its section, its material and its bearings.

The beam can be steel (the well-known IPN sections, or wider HEB sections), timber, or reinforced concrete. Steel takes up little height, timber can be left exposed, concrete suits some short-span openings. The right choice depends on the loads, the span and the headroom available below the ceiling.

The bearings are as important as the beam: at both ends, the loads are concentrated on a small area. Padstones or posts often have to be created, and what lies below, down to the foundations, must be checked to take this concentrated load. This is the point most often neglected by openings "done by eye".

Finally, the study sets the propping plan: where to place the props, how many, and in what order to remove them.

1. Diagnosis and study. Visit, investigations, load path calculation and sizing. This is the stage at which you find out whether the desired opening is reasonable, or whether it is better to reduce or move it.

2. Authorisations. General meeting vote in a co-ownership building, planning formality if the façade is affected. No work starts before then.

3. Protection and propping. The rooms are protected, the services running through the wall are located and diverted, then props are installed on both sides to relieve the wall before any demolition.

4. Fitting the beam. The upper part of the wall is opened first, just enough to slide the beam in, then it is set on its bearings and the gap between the beam and the masonry is packed so that it takes up the loads.

5. Demolition below the beam. Once the beam is carrying the load, the lower part of the wall can be demolished, the rubble removed and the props taken out in the planned order.

6. Finishes. Boxing in the beam, making good the reveals, ceiling, floor and paint repairs, reinstating the services. Our own masonry, plastering and painting teams carry out these steps one after another, which avoids idle time between trades.

In a co-ownership building, cutting through a load-bearing wall is an example given by the authorities themselves of work affecting the common parts. The general meeting must authorise it before it starts, by the absolute majority of article 25 of the law of 10 July 1965, that is, the majority of the votes of all co-owners. If the work involves appropriating or destroying common parts, the double majority of article 26 applies. Neither the managing agent nor the owners' council can give authorisation in place of the meeting.

The request is made by recorded delivery letter with acknowledgement of receipt sent to the managing agent, with the project file: this is where the structural study and a precise description make the difference. You can wait for the annual meeting or request a special meeting, whose costs are then borne by you. In the event of a refusal, the co-owner has two months from receipt of the minutes to challenge it before the civil court (tribunal judiciaire).

On the planning side, an opening between two rooms, with no effect on the exterior, generally requires no authorisation. Everything changes if the opening cuts through a façade wall: creating or enlarging an opening changes the external appearance and requires at least a prior declaration (déclaration préalable). And when work that alters load-bearing structures goes together with a change of use, for example a barn converted into a dwelling, the planning code requires a building permit (article R. 421-14).

In historic town centres, also check the local rules. In Chambéry, in the protected heritage area, the conservation plan can protect decorative features inside buildings: an interior opening is not always unrestricted there.

A price per linear metre found online says very little about your wall. A serious quote details at least five items: the structural study, the propping, the beam and its bearings, the demolition with removal of rubble, and the finishes. Comparing two quotes where one leaves out the study or the finishes makes no sense.

What makes the budget vary:

The width of the opening. The longer the span, the heavier the beam, the more the bearings are loaded, and the more resources installation requires.

The type of wall. Stone masonry, common in old Savoyard buildings, is not cut like a brick or concrete wall: the making good around the opening takes longer.

The loads carried. A wall carrying two storeys and a roof structure does not call for the same beam as a cross wall under a simple floor.

Access. Taking a steel beam up to a flat on an upper floor, without a suitable lift, needs preparation. Lifting is part of the quote.

What is around it. Electrical or plumbing services to divert, floors to join between two rooms that were not at the same level, ceilings to make good: this is often where the gaps between the estimate and the invoice are hidden.

That is why we do not give prices over the phone: we come and see the wall, we price each item separately, and the quote remains free.

An opening in a load-bearing wall affects the structure of the building. Damage that would compromise its soundness is covered by the company's 10-year structural guarantee (garantie décennale), for ten years from the day after acceptance of the work. It only covers the activities declared in the insurance policy: ask for the certificate before signing, and check that masonry and structural work are listed.

Building damage insurance (dommages-ouvrage), taken out by the client, that is, you, allows repairs falling under the 10-year guarantee to be funded without waiting for liability to be established.