# Filling gap between basement foundation wall and floor - material recommendations



## robbrown99 (Jul 1, 2017)

Hi, we had an internal foundation drain installed and with that a 'miradrain', which is basically a dimple mat that extends up the wall to channel the water in to the drain from the wall. While the wall does not actively flood out, there is some dampness and the idea WAS to install a vapor barrier on the roll and tuck it into that drain, so that moisture would just roll down the wall.

Fast forward a few weeks and after speaking with contractors: a) we will just be painting the wall with a drylock or similar; b) contractors all warned us that radon would now be a problem because of the 1" exposed gap around the perimeter. Their recommendation (and of a radon specialist) was to just chop off the dimple mat flush with the floor (or slightly lower) and then fill in the crack between the floor and the wall. Some photos:

https://www.dropbox.com/s/s2tzzx4j0o8r25c/IMG_20170624_111339.jpg?dl=0

﻿https://www.dropbox.com/s/zjdpvh79eefqejr/IMG_20170624_111353.jpg?dl=0

*Question: *What material should I use to fill the gap? Standard concrete such as quikcrete https://www.hardwarestore.com/650542/quikrete-concrete-mix-1101-110160 ??? Or will that crack at this joint? Should I be looking instead at some form of expansion resistant concrete? Maybe some form of concrete, let that dry then a sealant in the corner?

I have approx: 125 feet long x 3 inches deep x 1 inch wide.

Thanks


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## Bud9051 (Nov 11, 2015)

The first step I would recommend (if you haven't already done so) is to get a radon reading fro what you currently have, you need a reference to judge any progress or even the current need. Testing isn't expensive.

If your number is high my guess is, what you propose will not make a big difference. But that gap will make it difficult to operate the standard negative pressure venting system. Even if you seal the top as described the drain end is probably open defeating the exhaust fan. 

But first, test to see what level of radon you are dealing with.

As a note, the contractor who installed the drainage system should have explained about the potential difficulty and perhaps suggested a test before he took your money. All future sales of your home will be looking at any radon issues.

Bud


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## robbrown99 (Jul 1, 2017)

Bud9051 said:


> The first step I would recommend (if you haven't already done so) is to get a radon reading fro what you currently have, you need a reference to judge any progress or even the current need. Testing isn't expensive.
> 
> If your number is high my guess is, what you propose will not make a big difference. But that gap will make it difficult to operate the standard negative pressure venting system. Even if you seal the top as described the drain end is probably open defeating the exhaust fan.
> 
> ...


Bud, thanks. We got in touch with a radon specialist who suggested sealing the crack. He will be coming out next week to test and then figure out remediation if necessary.

No, he didn't warn us. Yes in hindsight would have been better to find someone that thought more about radon. However, here we are. We had a bad mold problem and appear to have replaced that with a potential radon problem.


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## Bud9051 (Nov 11, 2015)

Not a pro on Radon, but IMO, if you have a Radon issue it was already there from the start. Get a reading, big difference in how you deal with a 5 or a 500 number.

Bud


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## stadry (Jun 20, 2009)

in my experience, there isn't 10% of homes w/basements that don't have radon issues,,, my office is in the basement & i know if i sit in here 24hrs a day, 7d/wk for 10,986yrs, i may face health issues at my 11,060th yr - hopefully a cure for whatever i shall have contracted will have been found

that being said, hang 6mm plastic from your top course & tuck it behind the miradrain,,, that remedies the issue BUT also traps wtr vapor promoting mold & mildew

install a radon evac system,,, drill a 3" hole in your sump's cover, insert pvc pipe, add a timer-controlled exhaust fan, & go sit outside to clear your lungs,,, you could also leave the walls as they are at present & install a fresh air exchanger 

drylock-type products are, impo, good for 1 thing - helping the drylock-type products plant's owners buy bigger boats,,, we never use it UNLESS a client specifically asks for it,,, even then, we try to divert to xypex instead,,, ymmv


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## stadry (Jun 20, 2009)

*Yippee !!!!!!!!!!!!!!*

ps - nice looking job


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## Canarywood1 (May 5, 2012)

robbrown99 said:


> Hi, we had an internal foundation drain installed and with that a 'miradrain', which is basically a dimple mat that extends up the wall to channel the water in to the drain from the wall. While the wall does not actively flood out, there is some dampness and the idea WAS to install a vapor barrier on the roll and tuck it into that drain, so that moisture would just roll down the wall.
> 
> Fast forward a few weeks and after speaking with contractors: a) we will just be painting the wall with a drylock or similar; b) contractors all warned us that radon would now be a problem because of the 1" exposed gap around the perimeter. Their recommendation (and of a radon specialist) was to just chop off the dimple mat flush with the floor (or slightly lower) and then fill in the crack between the floor and the wall. Some photos:
> 
> ...




Probably a shrinkage compensating grout for an area that small, the nice thing about it is you can place it in a plastic or flowable state, whatever works best for you.


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## Nverlost (Jul 4, 2017)

This might be a costly solution but I've used Drylock's hydraulic cement before with long term successful results. I had a shorter span than you do though so I only needed a couple of buckets.


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## stadry (Jun 20, 2009)

if you seal the miradrain to the wall, any water running down the wall will be unable to reach the drain & sump,,, therefore it'll wind up on the floor OUTSIDE of the drainage system & negate the sub-floor drainage system,,, with acknowledgements to the contrary solution posters, the method i suggested is the only way to accommodate both your radon concerns + water leaks,,, radon will be resolved IF you install the exhaust fan


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## jomama45 (Nov 13, 2008)

I'm with "staydry" on this one 100%. Ask to see your "radon professional's" credentials, he probably worked at Best Buy or McDonalds 2 months ago and is now an "expert" in radon.

If he can't figure out how to remediate radon in your situation with the open toe drain, he has no business taking peoples' money for radon mitigation. And if he proposes sealing the toe drain to the wall, make sure he offers you a warranty for a dry basement for at least 10 years, as I'm sure his practice will instantly void the foundation waterproofer's warranty..........


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