Answer: minimum slope rules apply for roofs depending on the residential area and sites more or less exposed to the winds.
The minimum slope of a roof depends on the exposure of the roof to the prevailing climate and winds. In France, three distinct climatic zones define the legislation applied to the slope: zone 1 includes the entire interior of the territory and the Mediterranean coast with altitudes below 200 meters. Zone 2 concerns the Atlantic coast for altitudes of 200 to 500 meters. North of Lorient, the strip located between 20 and 40 km from the east coast in this area; to the south, it is the entire strip located between the ocean and 20 km from the coast. Zone 3 consists of the Atlantic coast, the Channel and the North Sea over a depth of 20 km. Altitudes of at least 500 meters are also found in this area. The sites, which represent the prevailing winds, are the second criterion for determining the slope of the roofs. The normal site consists of plains or plateaus. The exposed site concerns the interior of the country, namely the high mountains or the valleys with strong wind, as well as the coasts on a depth of 5 km, the small islands or the top of the cliffs. Finally, the protected site concerns the places protected by the prevailing winds. Depending on the type of cover chosen, the minimum slope can be determined.