How to fix small gaps between garage floor & cinder foundation

SparklingWaterAugust 19, 2014

Hi. Seeking advice on what compound to use to close a small gap (1/2-3/4" in spots, others 1/4") between our garage cement floor and the foundation cinderblocks that have developed over last fifteen years. The gaps may be present due to any number of reasons but the point is, it needs fixing to avoid mice entry. Structurally, everything is sound with the garage and has been inspected.

Cement has been advised as impervious to animals and permanent. Sounds good. Is there a quick dry cement which contains itself so it doesn't spread under and out. Who do you hire to do such a job? Ambient temperature will be about 75 degrees when work is done this fall. Any other compounds you recommend? We do not want to install spray foam here (or there).

Thanks for your help.

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Do this yourself and save hundreds of dollars. Go to a big box store and buy the following:

1 60 lb bag of sand mix (this is concrete mix without the pieces of gravel)

1 mixing tub (a heavy duty rectangular plastic tub for mixing small quantities of concrete)

1 small trowel

Your total cost for all of this will be about $20.

Dump out maybe 10 lbs of dry concrete mix in the tub, add water per directions, mix with the trowel, and go around and place cement in the gaps; trowel flat. The concrete will start to set up within an hour. Don't make a soupy mix (to much water)...just add enough water that the concrete is uniform gray in color and fairly "stiff". And don't worry: it's not going to run anywhere.

    Bookmark   August 19, 2014 at 1:40PM
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You're the best kudzu9!

I am a big DIY'er and it strikes me I can handle this. Heck I just crawled around and insulated a crawl space last week. When my DH got nervous about the cement spreading down and pushing against the foundation, I thought I better ask.

I fully get you need to make the compound not to soupy, kind of like toothpaste consistency (maybe little more moisture) just right to "lay" in the space that's already there. As long as ambient temperature doesn't affect concrete (and I know very cold does), then I should be good to go with this fall project.


    Bookmark   August 19, 2014 at 3:03PM
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I'm glad you're up for this. You won't have any problems. When you mix up the concrete, the temptation is always to add too much water because it makes the mixing easier. Use the proportions given on the bag, and add water slowly. If it gets too moist, just add a little more dry mix. Below is a link to a 30 second video that shows you what you will be aiming for. Even though you will be using sand mix, and not regular concrete, you are still aiming for the consistency shown in the video. Also, you don't need much volume of concrete so start with a small batch.

When the consistency is right, go around and force it into the cracks, leveling off with the trowel. Don't worry about it running under the foundation or putting pressure on it: the odds of that happening are slightly less than me getting elected as next Pope.

Here is a link that might be useful: Concrete working consistency

    Bookmark   August 19, 2014 at 4:39PM
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I've been watching :LOTS of concrete patching

The ideal consistency is like a good box-mix brownie dough - the kind you have to spread out with the spatula.

Letting it sit for a few minutes and then doing a second mixing seems to be part of the process.

    Bookmark   August 20, 2014 at 1:14PM
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