Hi everyone,

I am looking at a house with an unfinished basement. The floor is poured and the walls are block. My question is, even If radon levels came back good, what happens when I start punching through nails for a subfloor and walls? Can that let the Radon back in?

In addition I may get a sump pump in, when I dig for that am I also at risk? It is a septic based house so I would not be draining into city sewer. THe house is located in Milford PA so I think radon has issues there.

Thanks,

John

 

I have included a link that you may find answers to your questions in.
I would not pipe your sump pump into the septic. If you are only using it for ground water removal, pipe it to the yard away from the house. Good luck.

http://www.epa.gov/iaq/radon/index.html

 

http://www.epa.gov/iaq/radon/construc.html

If you look here it says to protect they seal around the concrete so how would I seal where and when a nail goes in?

 

Have you considered installing a Radon Mitigation System? This negates any issues with radon levels going up due to drilling or other changes in air flow.

 

Im just reading about that now, wondering what the cost would be...

 

I'm in the mid-west so prices may differ, but my RMS costs $900 but the french drain was already installed so that may have made a difference. The company also paid to have another radon test done after the system was installed to verify that the levels had dropped.

If you haven't bought the house yet ask your realtor what the common practice is in your area. In some areas it's common to split the cost of installing a system, in other areas it's common for the seller to pay the entire cost.

 

"what happens when I start punching through nails for a subfloor and walls? Can that let the Radon back in?"

Block is porous and held together with mortar joints- radon gas (if present in your soil) will get in regardless via the stack effect (tendency of heated air rising in the home to create negative pressure in the basement relative to the exterior. This negative pressure "sucks" the gas in through the porous block.

Also, Radon is a tricky beast- Radon coming back "good" in a home inspection doesn't mean you'll NEVER be at risk for exposure! It can fluctuate with local soil, drainage and geographic conditions over time. When we bought our house the radon test came back 8 pCi/L. The test was performed in May '03. Just had it tested again in January '06 at the start of a basement remodel and it came back 3.7 pCi/L. A long term test battery is probably a better indicator if mitigation is required. However an 8 pCi/L upon "inspection to buy" did allow us to negotiate $1000 dollars off the closing cost to cover future mitigation activity!

Punching a hole in the slab can also let in radon if present. It's one of the three major ways it can infiltrate:
1.) Uncovered Sump Pit
2.) Unsealed Block Walls / Slab (try a websearch for RadonSeal to mitigate if levels come back > than 4pCi/L or lookup "subslab depressurization") Costs Usually run around $1000 to $1300.
3.) Unfilled Cracks / Joints in the concrete.
4.) Can also infiltrate through well water but thats not so common...

You probably shouldn't be punching holes in Block walls with nails in order to attach walls. Nail top plate of wall to the floor joists above. If you must attach something to the block wall consider construction adhesives like Liquid Nails.

Also, when you install the sump pit, if time, money and location allow you to, consider installing a 4" natural gravity drain from the sump pit under the footer to an external ditch away from the house, allows flexibility in terms of finishing the basement. Our Sump pit has this feature! The house was built in '94 and we bought from the original owner. He never had to use the sump pump, in 3 years of owning I've never had to use the sump pump, and the basement is bone dry! I attribute alot of that to the gravity drain. I have removed the sump pump in my setup like this and will throw a cover over it, and then carpet over it. I'll still be able to get it open, and I'll keep the sump pump around of course. But if a 4" gravity drain can't keep up with any water leaking into the interior drain tile under the slab I either have a dead woodchuck trapped in it on the outlet side, or the world is coming to an end!
If its the woodchuck: I uncover, plug-in, and pump; if it's the latter there are probably more important things to worry about... LOL

Best of luck

Jason

 

The house in question has no interior drain. Its looking like a higher priced house more and more.