Water does not drain from the flat roof of the garage

Hello dear forum,

we are building with a developer and are shortly before the handover of the house. We noticed that there is about 4-6 cm of water standing on our garage over almost the entire surface. Behind the garage, a gutter was installed and on the roof, roofing felt was applied by the local roofer.

It is obvious that the rainwater cannot be directed to the installed gutter because a slope was created towards the end.

We addressed this issue with our developer and were dismissed with the following words: Quote "The roof has to be greened anyway or put gravel on it, then you won't see the water. And if it rains enough, this highest point will be exceeded and the rainwater will be directed into the gutter."

We are very surprised by this response and rather assume a defect in the implementation or in the purpose of the gutter, which currently does not fulfill its function.

Furthermore, the contract states that the rainwater downpipe should be installed internally, which was not implemented that way. Our developer responded to this point as follows: "In the course of the construction progress and coordination with the roofer, we decided on a gutter. Since this is a minor deviation, we did not inform you about it."

BANG!!

Is anyone here able to help us? For clarification, I have attached a few pictures.

Many thanks in advance for your answers!!

[ATTACH alt="wasser-auf-unser-garagenflachdach-laeuft-nicht-ab-649499-1.jpeg"]83368[/ATTACH][ATTACH alt="wasser-auf-unser-garagenflachdach-laeuft-nicht-ab-649499-2.jpeg"]83369[/ATTACH][ATTACH alt="wasser-auf-unser-garagenflachdach-laeuft-nicht-ab-649499-5.jpeg"]83372[/ATTACH]

Whether greened or not, every roof must be constructed with a slope. If nothing drains, it appears that there is no slope and thus a defect.

For our carport, sloped insulation was used towards the downpipe to prevent something like this from happening.

Standing water also freezes and that is not good for the roof. If a very small damage occurs in the roof membrane, standing water can penetrate over days as opposed to draining directly. The only thing that comes to mind is:

Good morning, is it allowed to green a bituminized roof!? I always thought that a specific membrane had to be used...
Best regards

An external gutter is always preferable to me personally compared to an internal one. In case of damage, internal is always "worse." Nevertheless, to me (as a layperson) it looks defective. The slope is simply executed incorrectly. A green roof is good, by the way, it protects the roof membrane and according to our roofer and structural engineer leads to at least twice the lifespan. Also good for the microclimate and the insect world. But of course it must also be executed professionally (foil, substrate, drainage, etc.) Do you have professional construction supervision that speaks for YOU with the structural engineer / general contractor? If not, it might be high time to find someone? No layperson can correctly identify and classify all defects. For that, you need experts. House construction usually involves a lot of money, often the biggest expense in life. Nobody wants to be solely responsible for that as a construction layperson...

What exactly is stated in the building description and the plan regarding the roof construction?