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globus999 06-16-2010 12:18 PM

Basement subfloor and Radon - ideas?
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 06-16-2010 01:16 PM

do you have a sump pit?

globus999 06-16-2010 02:17 PM


Originally Posted by gmhammes (Post 457131)
do you have a sump pit?

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 06-16-2010 02:31 PM

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

Hohn 06-16-2010 02:38 PM

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

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