Radon Intrusion – Looking for advice on sealing large slab-to-wall gap
I’m looking for some advice. I have an existing radon mitigation system/fan, but my entire basement has a roughly 1–2 inch gap between the concrete slab and the cinder-block foundation walls.
Is this something that can be properly sealed with backer rod + polyurethane sealant, or is a 1–2 inch gap too large for that approach? I’ve seen recommendations for backer rod and sealant for smaller gaps, but I’m not sure what the proper approach is for something this large.
Also, is this generally a reasonable DIY project, or would you recommend having a radon mitigation contractor handle it?
For some context, my 1-month average radon level is around 3.1 pCi/L. That’s still below the EPA action level of 4.0 pCi/L, but given that I already have an active radon mitigation fan, the level seems a little higher than I would have expected.