Long live the light under the roof! Full of charm, attics and attics offer both conviviality and space saving. Provided they bring light. Here are our tips ...
Formerly converted granaries for the holidays in improvised dormitories, the roofs are nowadays laid out with the same care as the lower floors, which they contribute to ventilate, for the benefit, for example, of a larger and more open living space. on the ground floor. And then, by the sea where extensions are prohibited, their transformation is often the only solution to enlarge.
Lighting attics: a motivating but technical project ...
Under the roof, gaining habitable square meters often requires the services of an architect who will make the most of the volume: modification of the frame, lowering of the floor, choice of stairs, creation of storage ... To be arranged in the condition, at least 50% of the ground surface must be exploitable (height under the ceiling greater than 1.80 m), knowing that all the parts too low for it to be able to circulate there can be reserved for the storage, even , for those who tolerate it, for uses that do not require a standing position for its occupants: bathtub, headboard ...
To save space, one may be tempted to choose a steep staircase (step height greater than 20 cm) and to make it arrive a little low under the frame to reserve the clear parts to the rooms. But it is often at the expense of comfort and security. The arrival of the stairs will be preferably under the ridge which has a good height. Right or two flights, the "ideal" staircase requires a large hopper. Between the two, the spiral staircase is less cumbersome.
What glazed area and how many windows to provide?
It depends on the surface of the room: plan at least 2 roof windows of 114 x 118 cm for 20 m2. Several contiguous windows (4 windows in 55 x 78 cm or 78 x 98 cm, sizes adapted to the rooms of less than 5 m2) make the effect of a "bay" which opens the space (to envisage protections to avoid l greenhouse effect to the south!). Several small contiguous openings illuminate better than a single window of comparable size.
According to the specialist of the Velux roof window, the secret of "the perfect view" lies in the choice of the length of the window according to the slope of the roof. A sloping roof will accommodate short formats while long windows will be reserved for roofs with a low slope. The lower edge of the window should be about 90-120 cm above ground level and the top edge 2 meters above ground level. More expensive, the seated dog window has the advantage of offering a vertical view. But it brings about 40% less brightness
Enlarge the space by structural changes
Good news, the truss structures (W-shaped, impassable as they are) can be modified and even give style to a contemporary layout. As the entrance of old frameworks too low that it is necessary to modify to release a passage, they imperatively require the intervention of a specialist (and the technique of a meticulous plasterer during the installation of the plasterboard).
If the ceiling height is still insufficient, can the floor level be lowered or the perimeter walls raised, provided that the structure of the framework allows it? Ultimate and expensive recourse, the elevation of the roof ... The floor of the attic of old houses is generally strong enough to support the new load related to the development. "But in newer and lighter constructions, it is necessary to focus on light materials such as plasterboard or wood and / or strengthen the joist that carries the ceiling of the lower floor," says Pierre-Alain Texier, driver of work at Camif Habitat. A bathroom with plasterboard partitions, glass pavers and other heavy plumbing fixtures, weighs on the structure! Depending on the complexity of the site, the budget can vary from € 800 to € 2,000 / m2, on average € 1,300, according to Camif Habitat.
Sensation of space and fluidity
Even a surface of 40 m2 under a steep pitched farmhouse can look spacious and bright. This is the challenge raised by the architect Rozenn Sourflais, architect at the agency In and Out Architecture in Brest, in a house of the 50s in Conquet.
To succeed this bet, two rules were implemented: a lot of light thanks to 3-4 large roof windows oriented towards the seafront, a mezzanine room not to partition and a nice bathroom closed, welcoming a free-standing bath near the rampant open on the waves at this place. It was also lacking volumes to these two semi-detached houses located in Port-Crouesty, promised reunification.
Their many half-staggered levels required the intervention of the architect Sandrine Blot, DPLG architect at Anima Sarzeau. "The biggest difficulty was to give the link, the fluidity between all these reduced spaces and fragmented to create a marine loft atmosphere, boat deck spirit," she comments. The idea of development under the roof? Use the last two half-levels of the new building by creating a mezzanine with an office and a living room, and a room just above, overlooking the back of the house.
It also enjoys a sea view because its partition is punctuated by a glass porthole that allows the occupant to contemplate the port via the roof windows of the mezzanine. This layout, designed under large Velux windows open on the harbor, also has the advantage of lighting the ground floor now painted white, whose clarity in turn refers to the light upwards. In general, professionals advise to limit partitioning, or even blurring (half-partitions, glazed partitions in the upper part).
Insulate the roof for better comfort
The main source of heat loss, the roof is most often insulated from the inside. "The laying of mineral wool takes the order of 20 cm, to which must be added the thickness of the drywall," says Pierre-Alain Texier. Namely: for a slightly higher budget, there are thinner insulators (5 to 30 mm), for example in the form of aluminum foil layers, and just as effective, although more difficult to work. Insulation from the outside, when the roof is being repaired, preserves more space. She also has the interest to keep the apparent frame. A powerful window will always be less insulating than 30 cm of mineral wool even if, in the winter, it can contribute to warm the attic by the solar contribution!
For a good regulation summer and winter, install from the start motorized shutters. Advanced home automation, the Velux Active kit with external temperature sensors, automatically activates the motorized shutters to limit the use of heating in winter and maintain a temperate atmosphere in summer. A key, better interior comfort and energy savings! All these investments reduce the energy bill accordingly. Under these conditions, electric heating (convectors with inertia) often offers the best quality / price ratio.
Pierre-Alain Texier, work supervisor at Camif Habitat, discusses authorizations. The development of an attic whose surface is already counted in the living space (SHON) does not require work authorization. On the other hand, a preliminary declaration becomes necessary in case of transformation of a lost roof into habitable surfaces or as soon as one modifies the external aspect of the building (creation of seated dog, installation of roof window or enlargement of opening) .
All of this work is eligible for VAT 5.5%. The filing of a building permit is necessary for larger works that modify the load-bearing structure of the building (elevation). These works are subject to VAT 19.6%. Finally, it is mandatory to use an architect when the SHON of the house is greater than or equal to 170 m2. These rules can be strengthened and the instruction times increased in protected areas (historical monuments, nature reserves).