The application standards DIN 18531, DIN 18532 and DIN 18533 specify different minimum slopes in the area for the various areas of application.
While a minimum slope of 1.5% is sufficient for balconies, loggias and pergolas in accordance with DIN 18531-5, a minimum slope of 2% is required for the waterproofing of roofs covered with earth in accordance with DIN 18533-2 with bitumen/polymer bitumen membranes. However, this can be undercut if the waterproofing consists of at least two layers of polymer bitumen sheets. When waterproofing drivable traffic areas in accordance with DIN 18532-1, a minimum gradient of 2.5% is required.
For used/unused roof areas according to DIN 18531-1, 2% is sufficient for roofs in application category K2; Roofs of application category K1 according to DIN 18531-1 can also be planned without a slope under certain conditions.
The Flat Roof Directive, on the other hand, does not distinguish between areas of application, but generally specifies a minimum gradient of 2%. However, in justified cases, e.g. in the case of intensive greening or if the structural situation of the building does not allow for a slope, slope-free areas can also be provided.
What all current regulations have in common is that the slope specification defines the planned slope from which the actual slope can and may deviate due to permissible tolerances.
Source: bauwion
