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Sealing Cracks
Back in the late 1980 and early 1990 there was a company in Illinois that offered extensive sealing of foundations as a means of radon reduction, I happened to see some of the work and have to say it was better than my own.  The company would pull up the carpeting if present, grind out all visible cracks (wall and floors) and caulk them tight, sometimes even painting the floors.  All of this for a price of $800.00 to $1000.00 Dollars. The company did not offer any guarantees that this would reduce radon levels and as the EPA showed early on sealing alone when it does work has close to a 99% failure rate within one year, it's a temporary fix.  The point is most radon mitigation companies can do some caulking and install an active radon reduction system for the same $800.00 to $1000.00 dollar price range and give you a guarantee at the same time.  We went back and installed a radon reduction system in one of these sealed homes after the sealing alone had increased the radon levels.  The company that did the sealing is no longer in business.

What we seal at VSI.
Sealing is important, we're just not going to get carried away with it.  If you're remodeling your basement and replacing the carpeting then by all means have us come out after the carpeting is removed and before the new carpeting is laid.  Don't take up your carpeting just to seal cracks, as that is rarely ever needed.  We won't take down your paneling or drywall either.  As a general rule of thumb we caulk accessible areas where the floor and wall meet and cracks big enough to slide a credit card into.
Ideally if you are trying sealing alone to reduce your radon level we see the best results in unfinished basements.

The following pictures are examples of common and some uncommon areas we seal.  You can use the pictures and explanations as a guide to doing your own sealing.


Click on pictures to enlarge.

clean cold joint

Basement Cold joints (where floor and walls meet) are cleaned of loose debris before caulking.

Caulking Cold joint

At VSI we use a non toxic caulk so we don't create a indoor air quality problem while trying to fix one.  If you are caulking your own home the EPA recommends a polyurethane caulk for cracks and cold joints.  Be careful when using caulks recommended for outside, some can be harmful if used in unventilated areas.

Cleaning crack

Control joints are intentionally placed in the floor to help prevent random cracking of the slab. Some types of control joints have a plastic insert that helps prevent air flow even if the concrete cracks.  Those that don't should be cleaned and caulked.

Filling large hole

One way of sealing larger holes is to stuff newspaper into the hole and seal the front with a polyurethane foam such as "Great Stuff" available at most hardware stores.

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Radon Reduction System