Hi,

We moved into a new house last fall. We would like to seal the basement walls and floor, first to help keep radon out, but also to avoid dust/stains/condensation.

It appears as if the basement floor is already sealed as it has a sheen to it.

First, is it okay to seal the floor again?

Second, what product would I use on the floors/walls? I talked to someone at QuikRete and it sounds like I may have to use something on the floor that handles hydrostatic pressure? And the product to use on the walls sounded like a lot of work to put on. I have a friend who says they just sprayed something on and it sounded so easy.

Thanks,
Sue

 

I do radon testing in homes as part of my home inspection business and

have some experience retesting homes that had passive types of ''repairs''

done. One house I recall particularly was a very large new home that

exceeded the EPA threshold. The owner was an engineer who was certain

he could seal his basement tight enough to keep out radon. He was very

dissapointed after spending about a week and a couple thousand dollars

worth of high-tech sealing to every imaginable crack and void and his retest

came back only a few 10ths of a ''pico-curie'' below his initial test. I have

seen other attempts to seal out radon, where the retest actually showed

an increase. This is not an unusual phenominum, as other testers and

mitigators I've talked to have similar stories, and while the EPA no longer

oversees this area, their previous teaching material also says the same thing.

If you have a radon problem, call a professional or the EPA actually

published a do it youself book on how to install a radon reduction system a

few years ago. I don't remember the name, but I think I've got a copy

around somewhere.

 

Thanks for the info! We actually did have a professional come in and do the sealing. All we need is a few pico-curies We're at 4.5 and need to get it down to 3.9. Also, I've heard similar things that you're saying, that sealing may not help and may actually make it worse. So we thought we'd give it a try, retest, and then do the active if needed. I'd just prefer not to have to put a fan and long pipe running outside the full height of my home. Thanks!

 

There are radon sealing products for concrete on the market that you just spray on. You can find them on the internet by searching for radon seal. I have never used them and don't know if they really work, but a few of these companies are members of the BBB and they don't have any complaints against them, so maybe there is some merit to the products.

 

I just spent $500 on 4 5-gal buckets of a radon sealer. I have completed about 3/4th of the basement so far. Very easy to apply, you can actually see it soak into my poured concrete walls. Whether it works or not, I am not sure. The studies say it does help the concrete form a better barrier, but all concrete surfaces have cracks & concrete is very porrous. I did it as a preventative measure prior to begining my basement refinish. Since I did not test prior to application I will have no way to determine its effectiveness. I will probably test after I am finished with the basement remodel. I hae a 1 year old house & poured concrete wallls.

I spoke to a Commercial Contractor friend ofmine that has been a GC for 20+ years. He indicated on their commercial jobs, they spray on one of these types of products but he did not know which one of if it was the same chemical make-up. He did say it seems to make the concrete stronger & more durable.

FYI, when you search on the internet under "radon sealers" or "radon paint" you will find 5-6 different spray-on type sealers. All of them are manufactured by Endur-o-Seal. The base formula is the same in each & per the company spokesperson, there is effectively no differences between them. Thus I went witht the cheapest priced one, $125 per bucket & free shipping since I had over 3 buckets.

Good Luck. Mike

 

In many cases you can eliminate the pipe outside the house. If you do the

standard mitigation system before finishing the basement, an experienced

contractor can often route the PVC up the basement wall and if you have

an attached garage, run the pipe through the garage, into the garage attic,

where the fan will be installed. All you need to do then is run the discharge

pipe through a flashing in the garage roof, to the outside. The fan is

virtually silent, if you have a finished ceiling in the garage. The discharge

pipe on the roof looks just like a waste vent pipe that all houses have.

When you finish the basement, a few extra inches of space on one wall

will conceal the PVC between the studs and the poured wall. Sometimes,

with a little extra work, even the pipe through the inside of the garage can be

concealed. Did the person who did the radon testing tell you that levels

can vary seasonally and that your 4.5 pc/l could be a lot higher during

other times of the year ? What I'm saying is a 4.5 measured during a

typical 48 hr. period could be a 9.5 under other circumstances. Getting it

down .6 with passive efforts (I've never seen results that good) won't help

if you have seasonal spikes in your actual radon levels. One big advantage

to the active systems is your radon will always be less than 4.0, regardless

of seasonal spikes. Another thing your testing person may not have told you

is the finest state of the art radon equipment has a ''built-in'' plus or minus

of 25%. That means you might actually have a true level of anywhere from

approx. 3.5 to 5.5. The reason I mention this is if your only looking to shed

a few pesky pico curies, that may not be enough. Radon measurement and

testing protocols are not precise enough to give you the assurance you

need that a few pc/l will be enough.

 

Thanks everyone for all the info! What I was told is that they could not run the piping through the garage since the exhaust has to be out the highest eave on our house (to avoid the gases going right back in the house in open upstairs windows). We live in a 2 story house and the garage eave isn't the highest eave. I may try the radon sealing product, but I think there's some kind of sealing product already on the floor, and it sounds like you have to remove that first. I could at least do the walls pretty easily.

 

I would put a few drops of water on the basement floor. If they soak in then the floor isn't sealed. If they just bead up and sit until they evaporate, you probably need to strip the floor with muriatic acid before you re-seal it.

 

One more thing you can try in your quest for passive success in reducing

radon is to seal any and all return air ducts in your basement. There aren't

supposed to be return air registers in the basement, if there are, seal them

up. The biggest return air problem is sloppy connections at ductwork and

when the ''tin-knockers'' put the return air between the floor joists, the

sheetmetal end covers usually fit poorly. All this stuff can be cured with

drilling, screwing, nailing, caulking and duct tape. (not the cheap homeowners

grade of tape, but the professional stuff) OK, you want to know what return

air has to do with radon. When your furnace is drawing return air from the

basement and discharging into the upstairs, it is depressurizing the basement

and turns your heating/ ac system into an industrial strength vaccuum

cleaner. This causes more soil gases to be drawn into the basement, hence

higher radon levels. When I do a radon test, I usually cover the wide gap

at the piece of return air duct where the filter goes. If the end result of the

test would have been slightly elevated, this alone can give you a few tenths

of a PC/L less. ( if the results are an acceptible reading, then I tell the new

homeowner to keep doing the duct tape thing)

Another thing to consider, is if you had the 48 hr. test done, that is the

standard protocol for a real estate transaction, not neccessarily what you

need as a homeowner. The difference is a RE transaction has to happen with-

in a fairly short timeframe and whatever you can come up with in that time-

period is better than nothing. As a homeowner, you would be better served

with a passive type of radon tracking device. These are designed to be left

in the home for longer perods of time, like 30, 60 or 90 days. The object is

that a longer time period will more closely replicate a typical time period,

rather than a limited 2 day period when the barrometric pressure or some

other variable was out of whack. Most radon testing is done at a RE trans-

action, and most measurement providers (like me) don't have the kind of

equipment needed for the long term tests. I mention all this in the

assumption that your more interested in the health and safety of your

family than just trying to reduce some arbitrary number to a number that

you like.