Dear forum,
For our single-family house, we are planning a flat roof due to having 2.5 storeys. We have already discussed our plans with our trusted general planner. To get an independent opinion, we have commissioned an external architect to review and optimize the design. He has now recommended an internal flat roof drainage system. At first, I strictly rejected the concept. However, I must admit that it also offers (at least) aesthetic advantages. Perhaps there are also practical technical or structural benefits (no icing?), too...
Now to my main question: Do you have experience with internal roof drainage systems for flat roofs? Should we avoid them, or is proper installation not that difficult for a specialized contractor?
In our case, the downpipes would be routed down behind drywall partitions into the basement. Alternatively, would it be permissible or possible to "hide" the downpipes within the external insulation (ETICS 140mm (5.5 inches))?
It is an additional challenge for us that we must discharge surface water not into the sewer system but into an above-ground channel in the street. Since the connection point to the sewer is only 20cm (8 inches) above street level, I am wondering how to guide water from all four corners of the house to the street... The two rear corners are 15–17m (50–56 feet) from the street, while the two front corners are only 3m (10 feet) away. With external downpipes, I can somewhat imagine this, as there would at least be some slope. But how can this be implemented with internal downpipes? These only exit the building below the basement ceiling, so there is no longer any slope toward the street gutter...
On the left side, the path to the street is also "blocked" by a shed and, further on, by a carport. I simply cannot imagine how this could be laid out... Our flat roof will be greened, which will retain and delay rainwater discharge. Perhaps it would be better to aim for infiltration on our own property directly, or in combination with a soakaway?
I would be grateful for any creative tips!
Have a nice Sunday!
Regards
Stephan
For our single-family house, we are planning a flat roof due to having 2.5 storeys. We have already discussed our plans with our trusted general planner. To get an independent opinion, we have commissioned an external architect to review and optimize the design. He has now recommended an internal flat roof drainage system. At first, I strictly rejected the concept. However, I must admit that it also offers (at least) aesthetic advantages. Perhaps there are also practical technical or structural benefits (no icing?), too...
Now to my main question: Do you have experience with internal roof drainage systems for flat roofs? Should we avoid them, or is proper installation not that difficult for a specialized contractor?
In our case, the downpipes would be routed down behind drywall partitions into the basement. Alternatively, would it be permissible or possible to "hide" the downpipes within the external insulation (ETICS 140mm (5.5 inches))?
It is an additional challenge for us that we must discharge surface water not into the sewer system but into an above-ground channel in the street. Since the connection point to the sewer is only 20cm (8 inches) above street level, I am wondering how to guide water from all four corners of the house to the street... The two rear corners are 15–17m (50–56 feet) from the street, while the two front corners are only 3m (10 feet) away. With external downpipes, I can somewhat imagine this, as there would at least be some slope. But how can this be implemented with internal downpipes? These only exit the building below the basement ceiling, so there is no longer any slope toward the street gutter...
On the left side, the path to the street is also "blocked" by a shed and, further on, by a carport. I simply cannot imagine how this could be laid out... Our flat roof will be greened, which will retain and delay rainwater discharge. Perhaps it would be better to aim for infiltration on our own property directly, or in combination with a soakaway?
I would be grateful for any creative tips!
Have a nice Sunday!
Regards
Stephan
Traumfaenger schrieb:
Yes, we have the entire roof drainage installed internally and have no issues with it, neither noise from the water running inside the walls nor problems with frost or similar. We chose this for aesthetic reasons because the house is built in the Bauhaus style, and we wanted smooth surfaces without those ugly boxes on the walls. So, have you also shown this (for example, in the house pictures thread)?
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
T
Traumfaenger13 Nov 2021 21:1211ant schrieb:
So, have you shown this anywhere as well (for example, in the house pictures thread)?No, but I just sent you two pictures 😉P
pagoni202013 Nov 2021 22:21We had one of these planned. However, during execution it became clear that the original designer had mostly just drawn it without being truly familiar with the technical implementation. After the roofers raised their usual concerns and it turned out they hadn’t done this before either, I canceled it. The general contractor was actually relieved, even though he had suggested it for aesthetic reasons.
It probably would have looked quite good, but I have fewer problems with a gutter, which is simply necessary. I’d rather spend my money elsewhere.
If you decide to do it, you should be absolutely sure that the person carrying it out really knows what they are doing, because internal water drainage can logically cause issues; if done well, it probably won’t. THAT would be my critical point. When I see a gutter with the slope in the wrong direction, I immediately know that my decision to back out was probably the right one.
It probably would have looked quite good, but I have fewer problems with a gutter, which is simply necessary. I’d rather spend my money elsewhere.
If you decide to do it, you should be absolutely sure that the person carrying it out really knows what they are doing, because internal water drainage can logically cause issues; if done well, it probably won’t. THAT would be my critical point. When I see a gutter with the slope in the wrong direction, I immediately know that my decision to back out was probably the right one.