Flat roof construction

Flat roofs are forms of roof construction with only a shallow pitch, possibly even none at all, and a covering of an impervious layer of material over their entire area. The borderline between a shallow-pitch and a pitched roof lies at an inclination of approx. 18% (10°). Pitches below 2% (ca. 1°) are regarded as forms of construction on which water run-off is not automatically guaranteed, and pitches up to 5% (approx. 3°) are likely to experience ponding due to deflection of the roof structure and/or unevenness in the roof finishes