Build an extension: 6 rules to know

Build an extension: 6 rules to know

Nicolas Masurel Architect

The house that we love or that which is about to buy sometimes needs a little more space. Carry an extension Then the best solution. extra room on one level, extending over several levels or raising of roof ... Possible configurations are almost endless. Yet building an extension is a very demanding exercise, the first field followed by the planning rules. Two architects resolutely contemporary signatures recall the rules for extend the house.

A extension, those are square meters and more. But not only. By opening the space, we will rework volumes rethink traffic in the home, expand and facilitate access to the outside, on the terrace or garden. Through openings, the light will pour in, greatly improving the comfort and quality of life.  

Gilles Bertrand councils (AAGB Architecture Tours) and Nicolas Masurel (Koutok Architecture in Nantes).  

>> Read also >> wooden extension: the rules to know 

1. Use the architect thinking even when the law does not impose

You will necessarily to hire an architect to your extension project if the total area of ​​the project (after work) exceeds 150 m2 (or 170 m2 for building permit applications filed before 1 March 2017). However, even if your project is within these limits, the contribution of the architect is invaluable. Besides, more expansion is, the more it needs to be optimized ... 

"The architect will listen to the family, how it is made, is she going to grow? Do you receive a lot at home? Then he will consider all of the constraints and propose one or more projects"Explains Gilles Bertrand. "In general, I present the progression of my thoughts with a series of drawings as different tracks on which the customer can react or rebound", Continues Nicolas Masurel. 

The architect will work the shape of the extension, its volume and make the connection between the frames. If necessary and coherent, he propose to revise insulation, joinery, or the facade of the existing building. An architect has never twice the same project. Your extension is unique.  

>> Read also >> 60 m2 and a wooden extension 

Invisible from the street, this contemporary extension (wooden frame and zinc cladding) adds 70m2, on two levels, a beautiful House Tours. The ground floor is occupied by a vast kitchen, the'étage par un bureau et une chambre. La grande baie vitrée est en biais pour maximiser les apports solaires. Création Gilles Bertrand.

Invisible from the street, this contemporary extension (wooden frame and zinc cladding) adds 70m2, on two levels, a beautiful House Tours. The ground floor is occupied by a large kitchen, upstairs with an office and a bedroom. The large bay window is angled to maximize solar gain. Creation Gilles Bertrand.

Sébastien Andrei

2. Identify constraints, make the forces!

Build an extension amounts to juggle a set of constraints, including: the planning rules and respect for property boundaries, the orientation of the plot and its surroundings, the footprint available, the terrain or the differences in height. The lights are rarely all green! 

"Constraints forced to turn and go back the project in every sense, to find solutions that integrate all criteria"Confirms Nicolas Masurel who sees these constraints as a creative challenge. "An expansion project is built by successive exchanges with the client, nothing is fixed initially must stay open. For example, the rediscovery of a beautiful stone wall of an old house can induce, in response, to use a wooden wedding / zinc on the extension."  

Even analysis for Gilles Bertrand: "a very limited footprint, manage parking for several vehicles, a slope, access to the pool, vis-a-vis, and of course, the limits imposed by the Local Development Plan (PLU). .. this is part of project data." 

>> Read also >> Before / after: a larger house in its own juice 

Wood Extension (ground floor) and elevation of wood'étage (enduit). On devine, au dessus de l'extension, la toiture d'origine. Bardage bois (red cedar) et menuiseries aluminium.

Extension wood (ground floor) and elevation wood floor (coated). We guess, over the extension, the original roof. Cladding wood (red cedar) and aluminum joinery.

Nicolas Masurel Architect

3. Dare contemporary forms

"The contemporary today, it is the traditional tomorrow, likes to remind Gilles Bertrand. Each period has its own architectural language and can be well in time and within an old frame or regional. The materials have a role to play in this dialogue. Zinc is both traditional and adapted to contemporary lines." 

Do not hesitate to build on today's codes, such as flat roofs or sleek but beware, contemporary does not necessarily mean cubic!  

Because they allow great creative freedom, Nicolas Masurel favors extensions timber frame. "On a recent project, located on a small parcel, we created several terrace levels. Finally, and despite the extension, the surface of the outdoor areas is higher than it was before the project."  

>> Read also >> 12 verandas to take as a model 

Extension of 103 m2 adjacent to a house in a small hamlet. The volume, fully encased in dark zinc, unfolds to connect smoothly both levels. Zinc offers a contemporary reading, like a shell deliberately detaching from the'architecture existante. Réalisation Gilles Bertrand

Extension of 103 m2 adjacent to a house in a small hamlet. The volume, fully encased in dark zinc, unfolds to connect smoothly both levels. Zinc offers a contemporary reading, like a shell voluntarily detached from the existing architecture. Directed by Gilles Bertrand

Philippe Hervouet

4. Go get light

When the orientation is favorable (south), a natural bathes home. "This is ideal because you can enjoy maximum solar winter flows, notes Nicolas Masurel. You just make sure that we protect the summer sun, with, for example, an external sunshades.  

But often, it must deal with a less obvious direction. "There are always solutions, continues Gilles Bertrand. One can create an angled bay to get some southern or patio in a still angle to capture the light from the south."  

We also think the double-height joinery (or glass walls) and skylights. The windows are also interesting for their ability to erase to erase the limit in / out. Think of folding windows, opening to large or spectacular sliding to post without angle.  

>> Read also >> glazed windows and Bays: our tips for choosing good 

5. Know the basics of thermal regulation

RT 2012 is considering the case of extensions ("new part of an existing building"). 

For small extensions (less than 150 m2 and less than 30% of created SHONRT area) a thermal regulation "lightened" applies much less stringent than for new and free from thermal study buildings. 

Recall that the SHONRT is the sum of the floors of each level surfaces, after deduction of non-heated surfaces (such as garage, a basement or attic not, an unheated veranda). 

For large extensions (≥150 m2 or ≥30% of SHONRT created), it will comply with the requirements of the RT 2012, that is to say achieve a performance level set by law, in terms of insulation and energy production. 

Admittedly, this is a sacred strain, partly because it will go through a thermal study phase. But you will gain a high-performance home, very little energy consuming and low emitting greenhouse gas (GHG) emissions.  

On a small plot, a wooden extension (with wood siding) enlarges the old house street corner. The garage has been reworked (one guesses in just the door). The'extension intègre des terrasses sur 3 niveaux, pour préserver une belle surface extérieure. L'ouverture sur le pignon de la maison ancienne a été créée lors des travaux.

On a small plot, a wooden extension (with wood siding) enlarges the old house street corner. The garage has been reworked (one guesses in just the door). The extension includes terraces on 3 levels, to preserve a beautiful outdoor area. The opening on the gable of the old house was created during the work.

Nicolas Masurel Architect

6. Understand the planning rules

The local development plan (PLU) in your municipality sets rules to follow. It can limit the footprint, the height of the extension, its bulk, location relative to the separative limit or prohibit certain colors.  

Also, if you live in a protected area or protected, your project will be subject to the approval of the Architect of the Buildings of France, whose mission is to ensure the architectural quality of the territory. Submit it your very upstream project.  

In areas not covered by a common planning document, the land law is governed default by the National Town Planning Regulations. Outside the urbanized areas of these municipalities, constructability is limited (extensions must absolutely be attached). Check with your municipality.  

contemporary extension of old buildings, consistency is ensured by the subtle marriage of materials (stone / wood / zinc). At the'origine, la maison était couverte d'un enduit ciment. La découverte des belles pierres a donné une toute nouvelle dimension au projet.

contemporary extension of old buildings, consistency is ensured by the subtle marriage of materials (stone / wood / zinc). Originally, the house was covered with cement plaster. The discovery of the beautiful stones gave a whole new dimension to the project.

Nicolas Masurel Architect

Good to know :

Building permit or statement of work?  

If you live in an urban area with a local development plan (PLU), you must file a permit application to build if: 

- work added a floor surface (also referred to footprint) greater than 40 m2 

- or if the work, adding a floor area between 20 and 40 m2, have the effect of increasing the total area of ​​the building (house + extension) to 170 m2 to 150 m2 from 1 March 2017). 

Note that if you create a floor area of ​​between 5 and 40 m2, you must file a statement of work. Below 5 m2 and if you do not change the external appearance of the house (eg, loft conversion without creating opening) you have no obligation.  

Where to find help to build your project? 

  • with the planning department of your municipality
  • or the Council of Architecture, Urbanism and Environment (CAUE) of your department

thanks to  

Gilles Bertrand, AAGB Architecture (Tours) - and www.aagb.fr Nicolas Masurel, Koutok Architects (Nantes) - www.koutok-architecture.fr 

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