DIY fix on a concrete floor crack.

May 12, 2015 6:42 PM

What are best practices for filling a long, dry 1/16" wide crack in my basement floor?

Ripping out my basement flooring revealed a crack down the middle, which splits in a Y shape to run throughout about half of the 900 sf basement. It is very fine- about 1/16" wide, in some places narrower.

The basement is very dry- no need for a sump pump, dehumidifier or anything. The crack is not leaking moisture of any type.

My gut tells me to seal it up somehow even if it does not seem problematic now. What is the best method and/or product to use to accomplish this on a DIY basis? Consider my handy woman/crack renovation skillset an amateur 8/10 (I can spackle/hang Sheetrock, repair boat fiberglass and do home stuff like install hardwood flooring myself).

The advice I've googled is varied enough that I turn to the hive mind's experience.

Thanks for the help.

posted by slateyness to Home & Garden (7 answers total)

You don't really need to do anything with a fine crack like that. If it were leaking moisture, the fix wouldn't be to seal the crack; it would be to fix your sump pump or footer drains. However if you must fill it just to satisfy your gut, then use a flexible caulk intended for masonry. Any rigid filler will just crack again.
posted by jon1270 at 7:20 PM on May 12, 2015

I'd leave it because trying to patch it is just going to make it look ugly. A big slab like that is bound to have a few cracks.
posted by bonobothegreat at 8:32 PM on May 12, 2015 [1 favorite]

Best answer: I would seal with caulk in order to prevent radon intrusion (you should also seal all the way around your basement between the wall and slab). Structurally, there is no reason to worry, but unless you are certain that radon is not an issue, it is wise to seal these sorts of cracks.
posted by ssg at 9:17 PM on May 12, 2015 [1 favorite]

They make cement crack filler, it comes in tubes and looks like cement, but I think it is plastic . I have used it. It is not too expensive for a tube. Be sure to get a sharp metal putty knife, not plastic, so you can drive the stuff in, and flush with the surface.
posted by Oyéah at 9:32 PM on May 12, 2015

Best answer: I would use Sikaflex. Do your best to make the crack clean and dry of course. And wear disposable gloves. This stuff is difficult to remove.
posted by Tunierikson at 11:25 PM on May 12, 2015 [1 favorite]

The thing about concrete is that it is going to crack. Your thin crack is nothing to worry about, as it does not indicate that the soil is shifting or the concrete otherwise failing. If you decide to put down ceramic tile on this floor in the future you should look into a rubber underlayment in that area. It is a foot or two wide, sticky backed, and covers the cracked area. This allows the slab to shift slightly without cracking the tile above it.
posted by Midnight Skulker at 7:42 AM on May 13, 2015

I have a crack about twice as wide in my (unfinished, concrete) basement floor, and my house requires a sump pump. The crack was there when I bought the house. I asked my home inspector about it and he said that the crack was nothing to worry about.

I've lived in the house for four years now. I've done nothing to repair the crack. It has not expanded, and the basement is still dry (provided the sump pump is working properly).

If I were you, I would ignore it, even if you were planning to put new flooring over it.
posted by tckma at 11:53 AM on May 13, 2015