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Hausbauer131 May 2018 13:06Hello everyone,
Until recently, I thought there were only two options for basement construction: the "black tank" and the "white tank," besides of course the alternative of having no basement. Meanwhile, I have learned that there are apparently also "brown tanks," and especially cautious (or maybe anxious?) people build a sort of black-white or brown-white tank, meaning they waterproof the essentially white tank additionally with bituminous coating or bentonite mats.
So far, I always thought the white waterproof concrete tank was the most sensible choice, as it is at least as watertight as the black tank and also cheaper. However, it seems that the white tank is not entirely impermeable to water vapor. I’m not sure whether that is a big issue. Anyway, I am reading increasingly about people who additionally seal their white tank with bitumen or bentonite to be on the safe side. In principle, that’s not a wrong approach, but it probably has a significant impact on costs.
Furthermore, there is a lot of discussion about the right insulation for the basement level. Most insulation materials are said to eventually get wet despite claimed water resistance, because they absorb water vapor. Only the somewhat more expensive cellular glass insulation seems to receive only advantages and no disadvantages. Which I find somewhat suspicious again.
So what do the very cautious do? They build a white tank, additionally seal it with bitumen or bentonite, then place the cellular glass insulation in front of it, and of course also seal that again with foil and bitumen. For a layperson, that sounds safe at first, but is that really necessary or is it way over the top?
I’m interested in the opinions of the assembled (future) homeowners. How did you build? How will you build? What are your experiences? Do you perhaps regret having chosen a particular setup? I’m curious...
Until recently, I thought there were only two options for basement construction: the "black tank" and the "white tank," besides of course the alternative of having no basement. Meanwhile, I have learned that there are apparently also "brown tanks," and especially cautious (or maybe anxious?) people build a sort of black-white or brown-white tank, meaning they waterproof the essentially white tank additionally with bituminous coating or bentonite mats.
So far, I always thought the white waterproof concrete tank was the most sensible choice, as it is at least as watertight as the black tank and also cheaper. However, it seems that the white tank is not entirely impermeable to water vapor. I’m not sure whether that is a big issue. Anyway, I am reading increasingly about people who additionally seal their white tank with bitumen or bentonite to be on the safe side. In principle, that’s not a wrong approach, but it probably has a significant impact on costs.
Furthermore, there is a lot of discussion about the right insulation for the basement level. Most insulation materials are said to eventually get wet despite claimed water resistance, because they absorb water vapor. Only the somewhat more expensive cellular glass insulation seems to receive only advantages and no disadvantages. Which I find somewhat suspicious again.
So what do the very cautious do? They build a white tank, additionally seal it with bitumen or bentonite, then place the cellular glass insulation in front of it, and of course also seal that again with foil and bitumen. For a layperson, that sounds safe at first, but is that really necessary or is it way over the top?
I’m interested in the opinions of the assembled (future) homeowners. How did you build? How will you build? What are your experiences? Do you perhaps regret having chosen a particular setup? I’m curious...
Regarding the waterproof concrete shell and the diffusion of water vapor, I can only say: I thought the same before. Then I did some thorough research and came across, for example, an experimental setup from TU Berlin and a publication from the "InformationsZentrum Beton." Both can be easily found with a quick Google search (unfortunately linking is not possible here in the forum).
Conclusion from both: If the wall is thick enough, no water transport from outside to inside occurs, whether liquid or vapor.
According to the WU (waterproof concrete) standard, walls are at least 20cm (8 inches) thick, if not thicker. In our case (Schwörerhaus), the walls are 24cm (9.5 inches) thick. We decided on a waterproof concrete shell (unheated) with perimeter insulation, which we installed ourselves.
Additionally, you should consider the indoor humidity in the basement (which might even be unheated). Hanging laundry there is probably not a great idea.
Of course, it’s also important to think about how you intend to use your basement. There are living basements, or by contrast, purely utility basements. There are probably intermediate options as well – this should definitely be part of your considerations.
And last but very important: What is the actual situation on site? How humid is it? Is it a hillside location? Is there standing or pressure water? What kind of soil is present? How is drainage allowed?
Conclusion from both: If the wall is thick enough, no water transport from outside to inside occurs, whether liquid or vapor.
According to the WU (waterproof concrete) standard, walls are at least 20cm (8 inches) thick, if not thicker. In our case (Schwörerhaus), the walls are 24cm (9.5 inches) thick. We decided on a waterproof concrete shell (unheated) with perimeter insulation, which we installed ourselves.
Additionally, you should consider the indoor humidity in the basement (which might even be unheated). Hanging laundry there is probably not a great idea.
Of course, it’s also important to think about how you intend to use your basement. There are living basements, or by contrast, purely utility basements. There are probably intermediate options as well – this should definitely be part of your considerations.
And last but very important: What is the actual situation on site? How humid is it? Is it a hillside location? Is there standing or pressure water? What kind of soil is present? How is drainage allowed?
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