ᐅ Concrete slab – vapor barrier against rising moisture

Created on: 30 Sep 2019 13:58
A
AnSe2019
Hello everyone,
in most constructions, you can see that a "membrane" (I can’t recall the exact technical term right now) is placed between the concrete slab and the masonry to prevent rising dampness.
In our shell construction, from what I could observe, this seems to have been omitted. Before I discuss this with the site manager, I wanted to ask for your collective knowledge to find out if this is normal, what the possible reasons might be, or other relevant information. Maybe my concerns will be resolved already.
I’ve attached a photo. If it had been done, you would see it, right?
Best regards
G
guckuck2
1 Oct 2019 18:48
Mottenhausen schrieb:

already sealed from below and therefore dry,

That is probably more wishful thinking than reality. The material itself may be waterproof, but it’s not made in one solid piece. In the simplest case, the panels are just butt-jointed. So, of course, there are gaps. Water can also run behind it from the sides.
B
Bookstar
1 Oct 2019 19:50
The concrete slab is waterproof concrete (WU) and watertight anyway. The purpose of the barrier is to manage residual moisture in the concrete; you could also wait for one year, then the vapor barrier would be unnecessary. But who has that much time nowadays?
A
AnSe2019
1 Oct 2019 20:03
Thank you all for the answers. I have now noticed the intended membrane in a few small spots, so everything is fine. But it’s better to ask or double-check when you’re not an expert.
M
Mottenhausen
2 Oct 2019 10:13
guckuck2 schrieb:

That is probably more wishful thinking than reality. The material itself might be waterproof, but it’s not made in one piece. In the simplest case, you have butt-jointed boards. Naturally, there are gaps. Water can also run behind the sides.

In our case, all joints are sealed with foam, and the external insulation on the sides fits seamlessly. In addition, there are polyethylene and aluminum foils under the rigid foam boards. That should make it reasonably watertight.