Terrace, veranda, garage, your extension project involves administrative authorizations that should not be overlooked. - IStock / City Presse

Before embarking on the creation of a terrace, the construction of a garage or the arrangement of the attic to create an additional bedroom, you must check the conditions under which you are entitled. In this regard, the Departmental Agency for Housing Information (Adil) - can provide you with information.

It is also advisable to ask the town hall for a "simple town planning certificate", which will tell you the state of the rules applicable to your land. If you wish to carry out a large-scale construction, prefer an "operational town planning certificate", which will also indicate whether your project is feasible.


In principle, any owner is free to carry out work at home, provided that this does not affect the structure of the building - when it is an apartment - do not modify the exterior appearance. of the facade and do not increase the living space.

In other words, you do not need authorization to lay a new floor covering, install a bathroom, tear down or add partitions (except load-bearing walls), insulate the interior of the dwelling… Note that in a building, a certain number of works can be submitted to the vote of the co-owners, in accordance with the co-ownership regulations and independently of administrative authorizations. This is the case for arrangements that affect the exterior appearance of the building but also the common areas, such as the creation of openings in the attic, the closing of a balcony, the installation of shutters or bars on the windows, or even the changing the color of the shutters.

A progressive procedure

Other works require planning permission. In this area, the degree of constraint of the procedure increases with the scope of the planned work. The prior declaration to the town hall is necessary to carry out minor improvements such as a facelift or the creation of a new footprint measuring between 5 and 20 m2. Provided that the final construction does not exceed 150 m2 of floor area, these dimensions may be increased up to 40 m2 on the ground, in areas covered by a local urban plan (PLU). In practice, it can be the creation of a terrace, a veranda, a garage, a garden shed built in hard (if it is removable, no authorization is necessary), or even an additional floor inside your house by transforming the attic, for example. The file is generally examined in the month following its submission. Once the project is accepted, the owner will have two years to complete it.

Beyond these thresholds, any extension of the dwelling or exterior creation implies a building permit. This is also the case when the site concerns a building listed as historical monuments or located in a protected area. The administrative authorization is translated here by a municipal decree. While these procedures are free, additional costs may be added to the price of the site, such as local taxes and the costs inherent in the intervention of an architect (compulsory from 150 m2 of construction).


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