French drain with radon concerns
DIY remodeling and focusing on the basement now. Last year I did a 48 hour(?) radon test and it came back a little over accepted limits. We also need to install a french drain to mitigate moisture issues. I’ve studied the french drain under the basement slab process and am ready to get cutting on the slab, but there seems to be a contradiction with radon mitigation.
The recommended french drain procedure is to place a dimpled plastic membrane about 6″ up the wall, and spanning across the footing into the trench to allow water from 1/2″ wall weep holes a path to the gravel/pipe drain. The problem is that also creates an air vent for air and radon under the slab to circulate into the occupied airspace. I can’t find any reasonable way to seal the top edge of the dimpled membrane. The one manufacturer said to use caulk on the 5/8″ gap, which sounds like a bad idea for multiple reasons.
I’ve also seen mention of attaching the radon vent to the french drain system to pull the air out that way, but with 160+ feet of perimeter, that’s a huge air intake that I wouldn’t trust to work properly.
What is the way to solve this so that fixing a moisture problem doesn’t create a radon problem? Is there any top sealed dimpled membrane that would work?
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