Improving radon air test results

Old 03-14-18, 05:49 AM
Thread Starter
Join Date: Jan 2015
Location: USA
Posts: 765
Received 41 Votes on 39 Posts
Improving radon air test results

My daughter and son-in-law are in the process of buying a home in Connecticut and obtained a radon air report as part of the inspection process. The test in the unfinished basement came back at 2.0, which is not a substantial problem in an unfinished basement. (In fact my understanding is that radon levels are highest in the winter so the average level over the year should be lower.) My concern is they are planning to finish the basement to create a playroom for my young grandchildren.

My overall question is what can reasonably be done to reduce the radon level. It appears to me that the standard means of mitigating radon isn't appropriate here because the current level isn't high enough to produce a meaningful decrease. Instead, this is what I have in mind:
  • Seal any cracks we can find in the poured foundation floor and walls.
  • Although there is no moisture issue, apply a radon sealant product on the walls and floor before finishing.

Can anyone comment on sealant products like Titebond Radon Sealant to seal cracks and RadonSeal or Drylock Extreme as an overall sealant? Are they worthwhile?
Any other suggestions?
Old 03-14-18, 08:17 AM
Join Date: Oct 2008
Location: New England
Posts: 10,524
Received 37 Votes on 34 Posts
Hi Tony,
I don't have experience with any of the sealants, but view them as bait for people looking for an easy low cost solution. Not trying to be insulting but we are asked all the time about products to seal out moisture and then frequently see people looking to address moisture problems where walls have previously been sealed.

Here is my suggestion. Since the house was not prepared for radon mitigation when built now would be a good time to install what is referred to as a passive vent which helps a little but puts in place the pipes where someone can just add the fan and it's done. Since CT has a lot of moderate Radon areas (some high and more moderately high) they could negotiate some allowance for that passive system. The air test was only a snapshot and does not guarantee lower numbers in the future. However, higher numbers will definitely need a system, so do it now.

As for finishing the basement, always a potential problem because basements are never built to be dry. Link added.

Old 03-14-18, 09:45 AM
Join Date: Jan 2010
Location: North East Kingdom of Vermont
Posts: 2,533
Received 1 Vote on 1 Post
Are you proposing to seal the entire basement floor and foundation sidewalls ?

If there is some seepage of Radon up from the underlying ground, and you arrest its movement through the sealed area, it will then simply move its path over to the unsealed area.

Ultimately, you want it to be directed outside altogether.
Old 03-14-18, 12:58 PM
Join Date: Nov 2012
Location: USA
Posts: 2,064
Received 161 Votes on 142 Posts

Is there a sump pump?
Because radon collects UNDER the floor slab, then diffuses upward,
so a sump pump pit can do double duty as the location for the radon collector.

Is there a floating slab - i.e. a gap between basement floor and wall?
If there is, then I would suggest considering a "perimeter unfinished" basement.
This means that when you finish the basement, you "build a room within the room"
and leave about a 3' gap between the exterior basement walls and the new interior finished walls. This helps with heating, allows you to access the drains etc, and would give the benefit of separating the basement living area from the most likely source of radon.

Does the heating system have some sort of furnace with a flue?
If it does, then you want the furnace to be open to the unfinished portion of the basement, that way the furnace draws the basement-radon-air and exhausts it through the chimney. Same idea applies to the clothers dryer, if you place the clothers washer and dryer in the unfinished portion of the basement, the dryer helps vent air that might have radon.
Old 03-17-18, 12:18 PM
Join Date: Dec 2013
Location: usa
Posts: 1,348
Received 1 Vote on 1 Post
easiest & least expensive is to properly prep & seal all surfaces w/non-moisture penetrating coating,,, IF there's a sub-floor water evac system w/sump, the sump lid can be refitted w/timer controlled exhaust fan & piping to exterior,,, an alternative is a fresh air exchanger

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: