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RadonSeal – Magic Sealer for your Basement?

RadonSeal – Magic Sealer for your Basement?
November 20, 2013 SNH Editorial Team

The next storm is coming- for sure.  RadonSeal promises  to seal your basement walls against water seepage, vapor efflorescence and even radon gas; resist hydrostatic pressure…” does it work?We tested it in a crawlspace with heavy efflorescence – the white build up or fall out from concrete bloc due to water seepage.  The space also had clear signs of water in the form of stains on the floor. RadonSeal was carefully applied according to the manufacturer’s instructions.


It is a pretty easy DIY project: (1) brush or scrape off the “white stuff” , (2) shop-vac the entire space thoroughly, and (3) spray RadonSeal, a the liquid using a regular hand-pumped garden sprayer.  It has been in place for approx. 7 months now.

The results are mixed: Yes, the efflorescence has not reoccurred. Check! I would even say the crawlspace feels a little less damp. Radon readings are way lower but RadonSeal did not hold back hydrostatic water pressure. During one heavy summer downpour with 3+” of rain water in a short period, water poured in.

It’s easy to read “resist” as stopping water from pressing in under hydrostatic pressure. Unfortunately, this did not happen in our test basement. It might have been worse without RadonSeal and perhaps RadonSeal prevents water from pressing in during less intense rain event but the fact remains it did not seal the basement against water infiltration.

So, is RadonSeal worth applying? In this test case the answer is: “Yes”.

(1) It lowered radon levels.

(2) The crawlspace is less damp and can now be used for storage of some, less precious items.

But at least in this test case, our thorough application of RadonSeal didn’t get us around the expense of an additional sump pump installation to catch water during heavy rain events.

Efflorescence on Concrete Bloc: