ᐅ Water does not drain from the flat roof of the garage

Created on: 20 Dec 2023 22:04
S
Sonneneck
Hello dear forum members,

We are building a house with a developer and are close to the handover.

We noticed that there is about 4-6 cm (1.5-2.5 inches) of standing water on almost the entire surface of our garage roof. A gutter was installed behind the garage, and roofing felt was applied on the roof by the local roofer.

It is obvious that the rainwater cannot flow into the installed gutter because the surface slopes upward toward the end.

We raised this issue with our developer and were dismissed with the following response: Quote, "The roof is going to be greened anyway, or you can put gravel on it—then you won’t see the water. And when it rains enough, the highest point will be exceeded, and the rainwater will flow into the gutter."

We were very surprised by this reply and rather believe that there is a defect in the execution or in the purpose of the gutter, which currently is not fulfilling its function.

Furthermore, the contract states that the downpipe should be routed internally, which was not done. Regarding this point, our developer responded as follows: "During the construction process and coordination with the roofer, we decided on a gutter. Since this represents a minor deviation, we did not inform you."

BANG!!

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

Thank you in advance for your responses!!

Top view of flat roof with puddle; behind it a modern white house.

On a gray flat roof, behind it fence, garden with stone wall and greenery.

View from roof onto green garden area, terrace with grill under pergola and construction work in the background

Exterior view of a white building with dark door, narrow window and visible gutter

White modern detached house with terrace and garden fence; further new builds in the background.
OWLer21 Dec 2023 12:45
hanghaus2023 schrieb:

What exactly does the construction specification and the plan say about the roof design?

Regardless of what is stated, a flat roof must have a slope. This has nothing to do with green roofing at all.
S
Sonneneck
21 Dec 2023 13:05
The construction description unfortunately does not mention any slope. For us, this was taken for granted since a rainwater downpipe was planned. Currently, the gutter is not serving its purpose.

You can find the relevant passage from the contract below.


Dokument: Planliste zur Massivgarage mit Abmessungen und Bauvorgaben
OWLer21 Dec 2023 13:10
But it also doesn’t mention anything about greening?
J
jens.knoedel
21 Dec 2023 13:18
By the way, there is a flat roof guideline or a DIN standard that requires a minimum slope of 2%. A slope of 5% is recommended. Therefore, there is an obvious defect, as the construction does not comply with the current state of technology.

Exception: green roofs with ponding water drainage – but you neither purchased nor received this.
H
hanghaus2023
21 Dec 2023 13:23
@OWLer the description could mention something about the green roof. Some development plans / building permits require it.
OWLer21 Dec 2023 13:26
hanghaus2023 schrieb:

@OWLer The description could include something about the green roof. Some zoning plans do require that.
Well, the uploaded excerpt doesn’t mention anything like that, and I imagine the implementation would be difficult since there’s a gutter at the front – basically, I would need a continuous parapet or something similar to prevent the granulate/ gravel, etc., from eroding and washing off the front.