Filling/sealing a gap in the crawlspace foundation

ralleiaOctober 30, 2010

Last week I was in the crawlspace underneath the bedroom addition and noticed daylight shining in. After picking out a piece of the loose mortar, I saw that there exists about a 5/8" gab between the original (1930) concrete block basement foundation and the add-on (1980?) concrete block crawlspace foundation. Someone had attempted to put mortar in the gap, however due to settling or concrete shrinkage this was now loose, leaving gaps or outright falling out.

What is the best approach to use to fill the gap? It's letting in a fair amount of cold, and is a possible path for rodents as well. I've seen some talk of polyurethane or semi-rigid epoxy sealers, but am not sure of the best approach.

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Polyurethane caulking.

    Bookmark   October 30, 2010 at 9:46PM
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Thank you--will get some and will try it out!

    Bookmark   November 1, 2010 at 10:58AM
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I have used "Great Stuff" , its messy and hard to work with, requiring much prep and planning, but it works well and is very durable.
But for a 5/8" gap, I dont know.
The caulking is much easier to work with and looks better.

    Bookmark   November 1, 2010 at 11:38PM
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Spray foam works great, too

    Bookmark   November 16, 2010 at 12:03PM
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Foam backer rod and polyurethane caulk will easily fill the gap (backer rod is much cheaper then the caulk).

There is no reason to fill more than a a small portion on each side.

    Bookmark   November 19, 2010 at 9:03AM
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