Basement soil gas control... really? - DIY Chatroom

gbwillner · 10-28-2009, 07:44 PM

Hello all,
I am starting to finish my basement and am currently finalizing plans. I am adding a sump pump in addition to a new slab to my 100 YO house in the midwest. I have now read about soil gas control- effectively venting the gravel beneath the slab up through the house to even out pressure differentials. Is this necessary? Can water-impermeable plastic be added beneath the slab without it? Is that recommended as well?

Thanks again!

Ebbo · 10-28-2009, 08:30 PM

I'm thinking Radon here. Some states it is code to have this. I know when I lived in New Jersey this was the case. Not so here in Florida.

http://www.buildingscience.com/docum...l-gas-control/

**thekctermite** · 10-30-2009, 05:23 PM

Agreed, nothing to do with pressure or equalization or anything like that.

Radon vents under the slab are not uncommon for the purpose of ventilating the radon that would otherwise get into the home, although the IRC code does not require them. There probably are jurisdictions that do require them I suppose (presumably by adopting the optional radon appendix in the IRC). If you're concerned about radon then it is smart to at least install a perforated 3" PVC pipe under the slab surrounded in gravel and stub it up for future installation of a fan-assist radon mitigation system.

6 mil polyethylene plastic is required...Not just recommended...Under any interior floor slab that will contain habitable space such as your basement. That's more for water/moisture than radon though.

gbwillner · 10-31-2009, 12:37 PM

Quote:

Originally Posted by thekctermite

Agreed, nothing to do with pressure or equalization or anything like that.

Radon vents under the slab are not uncommon for the purpose of ventilating the radon that would otherwise get into the home, although the IRC code does not require them. There probably are jurisdictions that do require them I suppose (presumably by adopting the optional radon appendix in the IRC). If you're concerned about radon then it is smart to at least install a perforated 3" PVC pipe under the slab surrounded in gravel and stub it up for future installation of a fan-assist radon mitigation system.

6 mil polyethylene plastic is required...Not just recommended...Under any interior floor slab that will contain habitable space such as your basement. That's more for water/moisture than radon though.

Thanks! Do you think it would be OK to hook up the gas vent to a plumbing vent? That way I can kill two birds with one stone.

Just Bill · 11-01-2009, 08:41 AM

Unless local code requires it, I would first do a radon test(kits available at home/hardware stores). And connecting it to the plumbing vent may not be allowed.

Yoyizit · 11-01-2009, 01:18 PM

http://cfpub.epa.gov/eroe/index.cfm?...747&subtop=343
Our house is just at the 4 pCi/L action level but we seldom go into the basement.