Anxious to have more space in their home and thus offer their family optimum comfort, more and more homeowners 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 find out about the necessary steps and to respect the thermal regulations in force to the letter. Otherwise, you may be forced to dismantle everything…
Steps prior to the extension of a house
There are 1,001 ways to expand your home and then enjoy a spacious, nicely decorated living space that is perfectly up to date. But before refining the details, we start by focusing on the essential steps to do before even starting the construction site. No question of attacking the expansion without authorization or permit. It should therefore be remembered that in 2020, in only one case no action is required, otherwise the following administrative procedures must be respected.
There is nothing to do if the extension is less than 5 m² in area, provided however that after the work the total area of the dwelling does not exceed 150 m².
Note: this must not be a addiction and the work must in no case change 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 filed with the town hall of the municipality before the start of the construction site if the owner must 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 (PLU) 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 imperatively be deposited at the town hall, again before the opening of the construction site, in the following cases:
- The planned house extension has a floor area or a footprint of more than 20 m² and the municipality is not covered by a Local Urban Plan or equivalent,
- The extension of the house to be created displays a floor area or a footprint of more than 40 m² and the municipality is covered by a PLU or equivalent.
- The total dwelling displays more than 150 m² of footprint or floor area after the extension works, regardless of the existence of a PLU or equivalent.
Interested parties are advised to take the time to compile a complete filethat 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 the plans of the facade, of the roof, of 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 the work is 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 produced in four copies, but certain plans must be produced in a much larger number of copies. It is necessary to have these points 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 dated and signed receipt. This is very important in case of exceeding response times.
Extending your house: when do you have to call on an architect?
Be careful to also respect theobligation to hire an architect if, once the expansion work is completed, the total surface area of the house is greater than 150 m² (and no longer 170 m² as was the case until March 2017). This means whatever the surface of the extension.
The owner can however refer to an architect for a smaller area, but in this case it is completely free and therefore not obligatory.
Do not hesitate to ask for tips and information by contacting either the Urban planning department of his municipality, either Consulting Service for Architecture, Urbanism and Environment (CAUE). In the latter case, you can be advised free of charge by an architect.
House extension: respect the thermal regulations in force
Set up for “reducing 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 surface 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 complies perfectly with the Thermal Regulations. The obligations are much greater when the extension exceeds 100 m² in area since the entire RT must be applied unconditionally.
It is crucial to be well informed on all these points prior to the start of construction, and even long before refining his project. The procedures may have evolved, the thermal regulations as well, moreover certain municipalities are subject to specific restrictions. However, no one is supposed to be unaware of the law… It is therefore necessary to take the time to take a short tour of the town hall of your village or town and also visit the government site. This makes it possible to take stock and therefore to strictly comply with all its obligations when it comes to home extensions. Refusing to submit to it can really be very expensive.