Slope of the flat roof - prevents puddles

Many flat roofs look like little lake landscapes from above. The puddles queue to finally be let through. The roof coating, whether made of bitumen or other material does not endure this load in the long term.

Moisture protection for the buildings - the slope at the flat roof

Hardly anything is more effective with a flat roof against penetrating moisture from above, than a sufficiently steep slope and good roof drainage.

Although there is no rule in Germany in the building regulations for the slope in a flat roof, but even out of pure selfishness you should measure it large enough. This will eventually save many repairs in the long run and possibly moisture damage to the ceiling.

One must always remember that the insurance company would not bear this damage. It usually pays only for damages caused by tap water, but not for rainwater.

Minimum gradient usually too little

The lower limit in terms of gradient is about two percent in Germany. That's just 1.1 degrees of incline. This slope would not be seen and perceived on most flat roofs.

Only when, after a few years or even months, the puddles on the roof, you will realize that this gap is too small.

Roofers and DIN 18531 for flat roofs recommend at least a gradient of five percent. Again, that's only 2.9 degrees, so still very little.

Material decisive for tightness with low incline

EPDM sealing membranes are made of ethylene-propylene-diene monomer, but the big advantage of this material is its production breadth. EPDM sealing membranes are available up to a width of 15.25 meters and a length of 61 meters.

Therefore, you have with this material in the best case, no seam on the roof. After all, it is the seams that are the fastest to leak in the conventional bitumen welding tracks.

In addition, the seams in bitumen often suffer from frost damage. Also in this area, the EPDM sealing membrane is much more resistant.

Tips & Tricks

If you want to be on the safe side, you should on the one hand at least choose a gradient of about 7 percent and on the other to grab the still quite new construction material EPDM as geomembrane.

Video Board: Repairing a roof ponding water area using RoofSlope - Starkweather Roofing