Sealing basement floor/wall gap

countryboy43

I'm planning to finish out my half basement and was wondering how best to seal the gap between the poured concrete floor and concrete block walls. After the floor was poured the concrete apparently shrunk leaving a gap that varies from about 1/8 inch to 1/4 inch around the entire perimeter.

My first thought was to brush dry hydraulic cement into the gap and then spray it with water. As the cement hardens it should expand and seal the gap. But then I was afraid that with changes in temperature the floor might expand/shrink breaking the seal.

My second thought was to try and force clear silicone sealant into the gap which would remain flexible should the floor expand or contract. But I can foresee a problem in getting enough sealant into the rather small opening to effect a permanent seal.

My objective in sealing this gap is mainly to prevent entry of water which happened once when the perimeter drain system failed due to grass clogging the discharge pipe. Sealing the gap would also prevent entry of ants which I've had some problems with as well as reducing the possibility of radon entry.

Any suggestions on how best to do this?

jomama45

Stay away from the hydraulic cement, or any other substance that isn't flexible, for the exact reason you mentioned.

I'd recommend installing a "backer rod" into any cracks over 1/8" and use a self leveling concrete sealant to close the gap with some flexibility. Sika makes such a product that should be available at a local big box store.

I would warn though, don't put a lot of faith in anything to guarantee that joint from leaking in the future. Proper monitoring & maintanence of the draintile, sump pump system is far more important in keeping a dry basement than that joint is.

countryboy43

The backer rod sounds like a good idea. I hadn't thought of that. Not familiar with the Sika product you mentioned but will check it out.

itsreallyconc

orange apron stores carry it but uncertain about blue, red, green, or yellow,,, orange also has sika polyurethane sealants.

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if you hear it from a guy in the apron store, be VERY suspicious the mtl/method will work,,, when it time to build something together, they won't answer phones NOR help
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jomama45

http://www.sikaconstruction.com/ht-c...Sealant-us.pdf

countryboy43

Thanks for the link to the Sikaflex data sheet. Thats sounds exactly like what I'm looking for to seal the joint around my basement floor/wall perimiter. Only problem is, none of the home improvement stores in my area show they carry ththe Sikaflex product and I've never had much sucess in getting items such as this from a distributor for DYI jobs. Some guys are selling this on ebay but there is no rhyme or reason to their pricing which ranges anywhere from $7 to $100+ per tube. Think this may be salvage material too.

However, I did find a similar self-leveling polyurethane concrete sealing product manufactured by Quikrete that is sold locally at the retail level for about $6-$7 per tube. Is this equivalent to the Sikaflex product and will it work just as good?
http://www.quikrete.com/PDFs/SPEC_DA...neSealants.pdf

bob22

Just remember, the self-leveling will not go vertical to fill a gap; it does what it says: self-levels, so it will go horizontally but not vertically. I used this in a joint between two concrete pads and it has performed excellently.

countryboy43

Self leveling sealant should work just fine since the gap around the basement perimeter is all horizontal.

There are several cracks on the vertical concrete block walls but they've never been a problem and I don't plan to do anything about them. Besides, there's no gap to fill on the vertical surface, just cracks in the blocks due to settling.