Extension of a home: how to do it? What is the budget?

The extension of a house is to be considered when you want to increase the area of ​​your living space. Having more living space improves the comfort of the whole family, and when the family grows, extending the house is often preferable to moving. Many solutions are proposed today allowing all budgets to carry out an expansion project. But before embarking on the work, it is important to know more about the new rules for building an extension and the cost of this extension.

House extension: what do the current regulations say?

Is considered as a house extension, a constructed living area provided that it is communicating with the house:

  • Either through a newly created opening,
  • Either through an opening that already exists.

Any type of room can be fitted out, whether it is a kitchen, a bedroom, a living room/living room, a bathroom or an office for example.

As long as the extension complies with the regulatory definition, this extension can therefore result:

  • From the development of a part of the house such as the garage or the attic,
  • The construction of a new work adjoining the existing house and which increases its surface area and volume,
  • Of an elevation of the house which makes it possible to add a floor.

The extension can be:

  • In various materials such as bricks, stones, wood, glass, concrete, etc.,
  • On stilts,
  • I don’t know.

It can also be a veranda or a container for example.

You can completely choose to develop the attic if you want to enlarge your house without lengthening the facade. It is a home extension solution that is quite common.

Each owner can therefore opt for the expansion solution that corresponds to his financial capacities, to the configuration of his land, but also to his tastes on the condition, however, that his project is accepted by the Local Urbanism Plan. Not all styles are systematically validated. The rules are particularly drastic when you live in a classified area where the architectural style and the harmony between the different constructions are important.

Extending your house: the mandatory steps

Consultation of the Town Planning Department, prior declaration of work, application for a building permit and declaration of the extension of the living area to the tax authorities are the obligatory passages. As for the thermal regulations, they must also be followed to the letter.

Urban Planning Department

As soon as one plans to build an extension of the house, it is necessary to go to the town planning department of the town hall of his commune in order to find out if it is possible and under what conditions. Town planning rules must be strictly adhered to. They vary from one municipality to another and may concern:

  • The materials used,
  • The color and/or the type of the coating but also of the joinery and the roof,
  • The distance to be respected between the extension and the boundary of the neighboring property,
  • The location of the windows,
  • The height of the new construction.

Request for authorization from the town hall

This essential step is linked to the surface area. It should be remembered that:

  • The prior declaration of work is sufficient if the extension does not exceed 40 M². It is done using the Cerfa 13703-05 form.
  • The building permit is required if the area of ​​the extension is greater than 40 M². The request is made using the Cerfa 13406-06 form.

Each Cerfa form is appended with an explanatory note and a list of supporting documents to be provided with the application.

The use of an architect is mandatory if (including extension) the total floor area of ​​the house is greater than 150 M². This does not exempt the client from filing an application for a building permit at the town hall.

Whatever the project in question, it is strongly recommended to inquire at the town hall in order to comply with the legislation. If this is not followed, the owner risks having to demolish his extension.

Declaration of the extension to tax services

Once the work is completed, the client has 90 days to declare the extension of the living space of his house to the tax authorities. This leads to a modification of the property tax and the rental tax.

To be in good standing with the tax authorities, you should complete form N°6704 and then send it to the tax department of your department.

House extension and Thermal Regulation (RT)

If we strongly recommend entrusting your house extension project to an expert, it is because the higher the surface area, the greater the constraints related to compliance with RT 2012. These obligations may, for example, relate to:

  • heating,
  • The integration of renewable energies into the expansion,
  • L’isolation,
  • Ventilation…

Extension of a house: what budget to plan?

The price of a home extension varies considerably from solution to solution. It depends among other things:

  • Of the surface,
  • From the inclination of the ground,
  • Du type d’extension,
  • materials used,
  • of the frame,
  • From the roof,
  • the complexity of the work,
  • Interior fittings,
  • Du type d’isolation,
  • of the heating system,
  • The number of windows, doors and bay windows,
  • Different services desired.

As an indication, it is necessary to count at least:

  • €1,000/M² for a wooden frame house extension,
  • €1,200/M² for an elevation,
  • €1,400/M² for a veranda,
  • 1,500 €/M² for an extension in concrete block.

If you have a very tight budget, it is in your best interest to choose an extension in Kit whose price per M² can be much lower than those indicated above.

Horizontal extension, elevation of the existing house or development of the attic: whatever the project, it is necessary to have a plan drawn up by an experienced craftsman or an architect.

It is of course possible to finance the extension of the house thanks to a bank loan at the best rate.

First of all, it is important to observe the safety and comfort rules to which the extension of the house must comply in order to be habitable. There is therefore no question of playing the architect if you do not have the essential expertise to carry out these major works. It is better to entrust most of the project to professionals whose know-how and expertise are recognized. Three or four house extension quotes are necessary to assess the budget to devote to this type of work and compare the proposed rates.

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