Flat roof, entrance canopy, water, EPDM

Hello everyone,

we have a wooden entrance canopy that still needs to be boarded and plastered.
On the flat roof without a slope! EPDM foil was installed for sealing.

Now the drain was positioned in such a way that quite a lot of water remains standing on the roof permanently.
It can accumulate about 3 cm of water before it drains. Of course, the water disappears over time if it doesn't rain, but it has already stood for several days at a time.

The carpenter received construction plans for the roof from the architect, but exactly how the drain should be positioned was not defined. The carpenter said he couldn't place the drain any other way.

According to the structural engineer, we are not allowed to slope the roof.
Now the question is, how critical is standing water on such a roof?

Hello,

the current standing water is a relatively small problem in terms of weight. You can easily calculate that yourself. It should already be taken into account statically, since a snow load must be considered in winter.

Gravel on the roof would also only help to a limited extent, as this does not create a slope to move the water faster to the drain. Without knowing the exact construction or work planning, nothing precise can be said.

From a structural point of view, there is almost always a solution if you use your brain in time. I find it very interesting that the emergency overflow is set lower than the normal drain. Would it still be possible to swap that if the downpipe is relocated?