Missing or incorrect fall
Without enough fall to the drainage, puddles form later. Standing water stresses the waterproofing and shortens its life.
Flat roof raw deck: what to check before waterproofing
On an open flat roof you decide whether water will later drain or stand. Falls, outlets, parapet and penetrations are still visible. Once the waterproofing is on, corrections often mean cutting open and rebuilding.
The most expensive defects on an open flat-roof deck
Unclear outlets and emergency overflows
Position, height and number of outlets plus emergency overflows at the parapet must match the drainage concept — otherwise water banks up.
Parapet without clean connections
Rough edges or unclear transitions at the parapet are the future weak points of the waterproofing.
Unprepared penetrations
Vents, balustrade posts and pipes must be clearly positioned before waterproofing. Subsequent cuts are permanent weak points.
Wet insulation gets enclosed
Insulation that has been rained on before waterproofing will no longer dry out underneath. The water remains in the roof structure.
What to document now before waterproofing
Check fall with water test
Pour water from a hose onto the surface. Where puddles still stand after ten minutes, fall is missing. Photograph these spots.
Outlets and emergency overflows
Photograph every outlet and emergency overflow with its surroundings. Check whether the lowest points match the drainage plan.
Parapet and connection areas
Document the full perimeter, especially corners and transitions. Free, sufficiently high connection areas for the later waterproofing are important.
Every penetration individually
Photograph each built-in part individually from close up. Location and type must be clearly recognizable before waterproofing follows.
Last chance before waterproofing
Upload your photos. We help you see which points to raise before the next work step.