Basement subfloor and Radon - ideas?

globus999

Hi,
I have a minor radon problem in the basement (below the "Action Level") but given the medical history of my family, I am not taking any chances.
To remediate radon, there are two options:

1 - concrete wall isolation
2 - active soil decompression

I am going for option 1 since option 2 is a crapshoot due to the unknown porosity of the soil under the slab. Long story.

For option 1, I am first treating the concrete (slab and walls) with a sealing compound (a reactive type, sodium-silicate based) to minimize the porosity of the concrete. On top, I'll paint with a gas-resistant water-based membrane (i.e. Blue Seal).
So far, no problem.

However, now I need to add a sub-floor and frame the walls.
The whole issue is that the sub-floor needs to have a high R value AND, here is the tricky part, the concrete should not be pierced (nor the walls nor the floor). Traditional sub-floor building process is to use 2x4 on the flat side nailed to the concrete. This is a no-no for me.

How about this?

Step 1: A sub-floor of 2x4 on the thin (not flat) side floating on the painted concrete on top a flexible layer of plastic sheet. Between the sleepers, expanded polystyrene. On top, traditional OSB T&G.

Step 2: Traditional framing for the walls, but nailed/screwed to the ceiling rafters and the sub-floor (not the concrete).

Would this be acceptable (Ontario, Canada)? or does the sub floor absolutely, positively needs to be nailed to the concrete?

Any ideas would be *very* welcomed!

Oh, I forgot. If the idea above is OK, how do I deal with the sloping near the floor sink? I mean, I think the concrete floor still needs to slope towards the sink but what about the subfloor? Does it need to slope too? Or do I just level it?

gmhammes

do you have a sump pit?

globus999

Nope. Not necessary. The basement is dry as a bone. Never had any problems...Yes, I know, if I had one I could have tapped it. But this is not the case. Besides, even if I had one, chances are the porosity is not homogeneous. This means, several holes in several places throughout the slab... ugh...

gmhammes

Gotcha. Hopefully some will be around to help you out shortly!

Hohn

Short of using an adhesive in lieu of mechanical fastening, nothing immediately comes to mind.