House extension: procedures, regulations before expanding your house

Anxious to have more space in their home and thus offer their families optimum comfort, more and more owners are opting for a house extension. It is also an excellent solution when you want to increase the value of your property. But to enlarge your house, be careful to learn about the necessary steps and to strictly respect the thermal regulations in force. Otherwise, we may be forced to dismantle everything …

Steps taken before extending a house

There are 1,001 ways to expand your home and subsequently enjoy a spacious, nicely decorated living space that’s perfectly in tune with the times. But before refining the details, we start by focusing on the essential steps to perform even before opening the site. No question of attacking the expansion without authorization or permit. It should therefore be remembered that in 2020, in one case only no action is necessary, otherwise the following administrative procedures must be respected.

No action

There is nothing to do if the extension is of an area less than 5 m², provided however that after the work the total area of ​​the dwelling does not exceed 150 m².

Please note: this should not be a addiction and the work must in no case modify the exterior appearance of the House. If this is the case, the owner must then submit a prior declaration of work to the town hall.

Prior declaration of work

The prior declaration of work must be submitted to the town hall of the municipality before the start of the work if the owner has to create a floor area or a footprint. more than 5 m² and less than 20 m².

However, it should be noted that if a Local Urban Plan (ENJOYED) covers the municipality in question, a simple prior declaration of work is sufficient to create a house extension of up to 40 m².

Request for a building permit

It must be submitted to the town hall, again before the opening of the site, in the following cases:

  • The planned house extension has a floor area or footprint of more than 20 m² and the municipality is not covered by a Local Urban Plan or equivalent,
  • The expansion of the house to be created displays a floor area or footprint of more than 40 m² and the municipality is covered by a PLU or equivalent.
  • The total home has more than 150 m² of footprint or floor area after extension work, regardless of the existence of a PLU or equivalent.

We recommend that interested parties take the time to compile a complete file, that is to say by attaching all the supporting documents that will allow the study of their case without wasting time. For example, it is necessary to provide plans for the facade, the roof, the location of the land, the sectional plan of the construction and the land, a 3D plan of the project in its environment, a ground plan, etc. Photographs of the land before work is done. also expected, as well as a certificate of compliance with the Thermal Regulations in force or documents relating to the calculation of the tax.

The building permit application file must be made in quadruplicate but some plans have to be produced in a much larger number of copies. These points must be clarified before preparing your file. This, once finalized, must be sent to the town hall by registered mail with acknowledgment of receipt or delivered by hand. against receipt dated and signed. This is very important if the response times are exceeded.

Expanding your house: when do you have to hire an architect?

Be careful to also respect theobligation to hire an architect if once the extension work is completed, the total area of ​​the house is greater than 150 m² (and no longer 170 m² as was the case until March 2017). This is understood regardless of the area of ​​the extension.

The owner can however refer to an architect for a smaller area, but in this case it is completely free and is therefore not compulsory.

Do not hesitate to ask for advice and information by contacting either the town planning service of his municipality, either at Architecture, Urban Planning and Environment Consulting Department (CAUE). In the latter case, one can be advised free of charge by an architect.

House extension: respect the thermal regulations in force

Set up for “Reduce the energy consumption of new buildings », The Thermal Regulations in force at the time of the work must be applied. With regard to RT 2012, it applies in a manner different depending on the size of the house extension. It is for example very moderate if the area of ​​the extension is below 50 m². For an extension of 50 to 100 m², the owner must, among other things, ensure that the energy efficiency of the extension fully complies with the Thermal Regulations. The obligations are much more important when the extension exceeds 100 m² in area since the entire RT must be applied unconditionally.

It is crucial to inquire well on all these points prior to the opening of the site, and even well before refining his project. The procedures may have changed, as well as the thermal regulations, and some municipalities are subject to specific restrictions. However, no one is supposed to ignore the law … It is therefore necessary to take the time to make a small tour of the town hall of his village or his city and also visit the government site. This makes it possible to take stock and therefore, to comply with all obligations to the letter in terms of house extension. Refusing to submit to it can be very costly.

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