mark2009March 2, 2009

March 2nd 2009. I applied Radon Seal per the instructions on the container. My results were no difference in radon readings. This is very disappointing.

Details: I live in Colorado just outside of Boulder, radon is an issue with many households here. I first measured my radon using a mail-in capsule a couple years ago. My readings were about 9.5. As a result of this I sealed all if the expansion joints in my basement (with a floor leveling product) and re-measured. New readings were ~2.5. So roughly a 75% improvement. This was during the Summer of 2007 so seasonal variations should not have been a factor.

I read that radon levels can vary based on the season and Winter levels are typically worse due the frozen ground and lack of airflow so I recently bought a digital radon meter. I measured using this meter about 2 months ago. Unfortunately my Winter readings were about 10. I then found RadonSeal on the internet. I only read a couple bad reviews so decided to risk the purchase. None of the reviews were very controlled, those with the best reviews also sealed their expansion joints etc. at the same time they applied the product. Since my expansion joints were already sealed, my readings should accurately reveal the results of Radon Seal I followed the application instructions to the letter and applied 3 coats of Radon Seal. I applied it to the floor and ~2 feet up the wall over the entire basement. I have a walkout basement so the concrete walls are limited. My readings before applying radon seal were from about 9.5 to 10.5 pcl. My readings after applying Radon seal are also 9.5 to 10.5. In other words the benefits of Radon Seal were zero.

Based on these results, I view RadonSeal as worthless. I contacted the manufacturer (they supposedly guarentee their product) but all I got were a bunch of excuses. I still have ~ 2 gallons left and would be happy to sell it to someone......

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There's probably more of a stack effect during the winter as well which would draw in more radon.

Not to get the thread off track, but I've noticed that upstairs is a lot better than the basement. The house came with a pipe going to the gravel under the slab. Maybe radon was the purpose, maybe not, but I rigged up a 15 watt radon fan to it and blew it right outside the house through a pipe, not to the roof. I guess the whole system is supposed to be under vacuum and routed up through the top of roof, but this is a lot less of a visual exterior impact, it works great and the electronic meter would let me know if there was a leak in the basement. I imagine someone would have to suck on that exhaust directly for a while to get a dose, and that it dissipates quickly.

    Bookmark   March 2, 2009 at 8:59PM
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Hi Mark2009,

I have a couple comments on your application and results:

1) There is no self leveling compound that will block radon gas. Your reduction in radon after the self leveling was temporary and radon would easily penetrate once cured.
2) 3 coats of RadonSeal is NOT appropriate for poured concrete, and;
3) RadonSeal would not be able to seal the areas covered by the leveling compound because the additives in those compounds prevent RadonSeal from reacting.

many inconsistencies in that report.

Best Regards,


    Bookmark   October 5, 2010 at 6:02PM
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Firstly, I don't find "many" inconsistency's with Mark2009's testing. It's the most accountable test I've seen while researching this subject, either from a user or manufacturer.

Secondly, the final decision should be based upon the warranty. Thoroseal has a 10 year warranty but for walls only. Hydra-block sealer, (which looked like a great product by the way) has a one year warranty from date of manufacture. RadonSeal's warranty is lifetime but...........not really when you read the fine print. Also, I've seen many reports from customers who say they got nowhere with warranty claims.

From what I've seen, contractor based products have lower warranties, products like hydra block. They are also very keen on contractor rigging and application and at almost $150.00 per 5 gal, who wouldn't be? So someone out there, please hire a professional who will spray a clear, water based liquid on your basement walls and floor and dries to look like your walls looked before application, a product with a one year warranty, and tell us all how it worked out.

    Bookmark   December 15, 2010 at 10:44PM
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well, I suppose we all have our own opinions about what qualifies as consistent data :)

since you mentioned warranties, I'm quite sure Thoroseal does NOT speak about radon gas in their warranty. Do they even claim to stop radon with their products? And what value is a one year warranty? Does that mean I need to apply every year? I believe that radonseal is the only sealer that speaks to radon reduction directly in their warranty. Now, whether or not they honor their warranty is another matter entirely. I suppose one could check with the BBB for any history on the company before doing business with them.

Best Regards,


    Bookmark   January 10, 2011 at 9:01PM
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Put in an under-slab vacuum system.

They actually work.

    Bookmark   January 11, 2011 at 8:24AM
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I am looking to seal the concrete walkway in front of our condo in the Florida Keys to prevent mildew and mold build up. Is this an appropriate product for that application and how effective can I expect it to be in such a moist climate?

    Bookmark   February 28, 2011 at 9:15AM
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I see these postings are old, however in case someone is looking...: My basement is ground level in the back, the other 3 sides are completely underground. I am going to be putting in a apartment but have damp & humidity problem and am considering Radonseal as a solution. Can anyone speak to its waterproofing claim? I am also curious if this product has an odor to it. I would gladly accept recommendations of other waterproofing products.

    Bookmark   September 17, 2011 at 5:23AM
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My experience probably won't be too helpful, but I also bought Radonseal. However, I wanted it to stop the excessive amount of efflorescence on my concrete basement floor. The website extolled its virtues for this purpose, so I went ahead and bought it.

My two reliable builder/remodeler guys followed manufacturer's directions exactly, and the efflorescence came right back following the two suggested applications.

I then had the guys install a good-sized dehumidifier, which runs 24/7. One of the men returned a few weeks later and did one extra treatment since there was still enough sealer in the can to apply it a third time. Same result. I read the information on their website carefully, and did a bit of research, but didn't find out anything expressly saying their product didn't work. I should have saved my $160 or whatever it was, plus cost of labor.

Now I have no idea what to do. I've considered applying epoxy-type garage floor paint over it, but doubt that would last, as the efflorescence itself is still going on underneath the concrete. Sigh.

I haven't tested for radon, but if Radonseal is this useless against salts coming up through unpainted concrete, I don't think I'd trust it for something as important as radon abatement. Good luck.

    Bookmark   September 25, 2011 at 7:43PM
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We recently purchased the RadonSeal Concrete Sealer and had very minimal changes. We tried calling them and their customer service was terrible. What a scam.... I would never recommend their company every. We did more research and when purchasing a product like the RadonSeal Product, it is best to buy from a more reputable company :(

    Bookmark   June 21, 2012 at 8:05PM
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Although political organizations (such as the US EPA) publish a variety of statements of elevated risk, to date (2010) there are no scientific studies that have ever actually shown that radon gas, as typically seen in houses, increases the risk of cancer. To be clear: There are NO valid studies that have conclusively demonstrated that typical residential exposures to radon increase the risk of cancer at all. In fact, all of the valid studies performed thus far show one of two things: 1) No risk and/or 2) a decreasing risk of cancer. This view is reflected in a position statement issued by the Health Physics Society, the premier Health Physics organization in the US. According to the position statement issued by the Health Physics Society1a, for doses below 100 mSv (10 rem)

    Bookmark   July 11, 2012 at 10:43AM
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Nevertheless, the Health Physics Society 's Environmental Radiation Fact Sheet states in part:

    Bookmark   July 13, 2012 at 9:54PM
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"[The] EPA does not recommend the use of sealing alone to reduce radon because, by itself, sealing has not been shown to lower radon levels significantly or consistently. It is difficult to identify and permanently seal the places where radon is entering. Normal settling of your home opens new entry routes and reopens old ones". EPA Consumer's Guide to Radon Reduction

    Bookmark   July 13, 2012 at 10:15PM
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"The EPA estimates."

They have no real valid studies to estimate anything on.

At one point they 'estimated" more radon lung caners in the Redding prong formation that the total number of lung cancers in the actual area.

There is simply NO reliable data.

No one has any.

If you want to reduce radon levels put in an under slab evacuation system.
Those have at least been show to reduce radon levels.

Any affect on actual cancer rates is not present.

    Bookmark   July 20, 2012 at 4:16PM
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I read through these posts and spoke with a rep at radon seal before placing an order with them. I personally found their customer service to be helpful.

During my discussion with them I mentioned the reviews on garden web and their response was that, concrete varies greatly! They did not deny - in certain conditions - it can be difficult to know if the concrete is even suitable for sealing with concrete sealers in general.

The problem I had was that after heavy rainfalls my garage floor would sweat. I sealed the concrete 4 months ago and so far it has made a all the difference.

I was guided through the whole process; prep, conditions, and application. The most difficult step in the process was removing stubborn oil stains (which I used Dawn detergent for). While sealing, I did notice that the sealer had a harder time absorbing into those spots (which I was aware may happen).

Why would I post a message to this forum? Well, I emailed them a positive testimonial days ago and they quickly issued a $20 refund to my credit card. I thought I should pay them back.

My 2 cents.

    Bookmark   October 12, 2012 at 11:13AM
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