The best is often to extend an existing roof, but an extension can also have a flat roof that gives it a touch of modernity. Especially if it's a green roof ...
The roof of an extension is a function of the desire to integrate the existing building. If you want it to be in the background, the best is to extend the current roof. If you want, on the contrary, to play on an aesthetic and architectural effect, the roof terrace (or flat roof) is a solution. This last option allows a simplicity of realization. "It is not always easy to harmonize an extension with the existing one," says Gérard Cornet, Camif Habitat architect and project manager in Poitiers, "We have to create an association that works between the two volumes. roofing, technically it is often simpler to build a roof terrace.An extension of the existing (return in "L" or "T") requires a recovery of the cover, of course, but also the frame, which are delicate operations. "
Beware of tightness!
However, creating a roof terrace is not a trivial operation. "The bituminous membranes, the zinc, the concrete slab offer good solutions, provided they are implemented in the rules of art," warns Fernando Calderero, head of the works department of the general contractor UTB. Attention, indeed, to the choice of the company which will work. Make several estimates, because the cost can be high (two to four times the price of a traditional roof) depending on the technicality of the realization and the number of speakers.
The main risk is that of leakage. The reason may be a bad treatment of singular points * or infiltrations due to penetrations during the installation of antennas or air conditioners for example. It is also possible to encounter disorders due to overload (too heavy a coating for the structure, accumulation of water after a storm due to lack of evacuation).
Also, consider regular maintenance of the roof terrace. Check several times a year that mosses and lichens are not invading the field. Watch for waterproofing structures and elements that may cause disturbances (access to the terrace, ventilation, chimney stubs ...). In addition, consider controlling and cleaning water outlets and overflows.
The advantages of a green roof
The green roof offers an undeniable aestheticism. In addition, it plays a regulatory role: rainwater, air quality (it absorbs dust, fixes CO2). It also improves summer comfort and improves acoustic performance. Its disadvantage remains its cost: to count a hundred euros per square meter.
* All sensitive areas of the roof, especially the joints between the cladding and roofing accessories (chimney stacks, etc.).