ᐅ Combining a flat roof with extensive green roofing and a terrace
Created on: 30 Oct 2024 10:38
S
Schwabe23S
Schwabe2330 Oct 2024 10:38Hello,
We have a carport/utility room with a 90m2 (970 ft²) roof that is accessible from the house. An extensive green roof is planned here, and the entire roof (timber frame with glued laminated timber ceiling) is already covered with an EPDM membrane, and the central drain is installed. The planting will be done on-site, and now it’s our turn. Since we didn’t expect how nice it is on the carport roof, we want to change our plans and use part of it as a terrace. From a load-bearing perspective, this is not an issue, and we can also meet the setback requirements. Currently, some water remains standing (1-2cm (0.4-0.8 inches)) because the roof has no slope.
I’m struggling with the best technical solution for the terrace section. Do you think it would work to lay the protective fleece used for the green roof directly over the entire surface and then place pedestals with protective mats on top of the EPDM membrane? On that, we would install an aluminum substructure and WPC decking boards. Should I expect frost damage or a biblical-scale insect infestation, or could the fleece wick the water away toward the planted area through capillary action?
Or would it be better to apply the full green roof build-up (fleece, drainage boards, separating fleece, soil) and simply use gravel instead of soil in the terrace area, with stone slabs or similar on top?
I’d be very grateful for any advice and thank you in advance for your help.
We have a carport/utility room with a 90m2 (970 ft²) roof that is accessible from the house. An extensive green roof is planned here, and the entire roof (timber frame with glued laminated timber ceiling) is already covered with an EPDM membrane, and the central drain is installed. The planting will be done on-site, and now it’s our turn. Since we didn’t expect how nice it is on the carport roof, we want to change our plans and use part of it as a terrace. From a load-bearing perspective, this is not an issue, and we can also meet the setback requirements. Currently, some water remains standing (1-2cm (0.4-0.8 inches)) because the roof has no slope.
I’m struggling with the best technical solution for the terrace section. Do you think it would work to lay the protective fleece used for the green roof directly over the entire surface and then place pedestals with protective mats on top of the EPDM membrane? On that, we would install an aluminum substructure and WPC decking boards. Should I expect frost damage or a biblical-scale insect infestation, or could the fleece wick the water away toward the planted area through capillary action?
Or would it be better to apply the full green roof build-up (fleece, drainage boards, separating fleece, soil) and simply use gravel instead of soil in the terrace area, with stone slabs or similar on top?
I’d be very grateful for any advice and thank you in advance for your help.
Although our situation is not exactly the same, we also have an extensive green roof with 0% slope and—in this case—a yet-to-be-built paved walkway leading to the side entrance of the house. I plan to install a pressure-resistant drainage stud membrane on top of the roof waterproofing, and then place only gravel and paving stones on it. I do not see any issues with this approach, and it is exactly what the manufacturer recommends.
In your case, I would prefer the solution with an aluminum substructure, as the pedestal supports are completely frost-resistant. For many substructure systems, there are side panels available as accessories, which could also be used as insect screens (although the bugs will probably find a way in regardless—just as they would with terraces installed elsewhere, which usually does not bother anyone). Another option could be to partially fill the cavity with gravel (while ensuring ventilation). However, you should install the slabs with a slope to prevent surface water from standing on them.
I would not install slabs on gravel or crushed stone, even if partially bound, without a slope in a basement area, as this is likely to cause long-term damage.
In your case, I would prefer the solution with an aluminum substructure, as the pedestal supports are completely frost-resistant. For many substructure systems, there are side panels available as accessories, which could also be used as insect screens (although the bugs will probably find a way in regardless—just as they would with terraces installed elsewhere, which usually does not bother anyone). Another option could be to partially fill the cavity with gravel (while ensuring ventilation). However, you should install the slabs with a slope to prevent surface water from standing on them.
I would not install slabs on gravel or crushed stone, even if partially bound, without a slope in a basement area, as this is likely to cause long-term damage.
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