I have a few lengthy cracks, 1.5-2mm wide. What special paste or mortar should I use to fix cracks in a concrete floor in basement? Can it be done with cement mix or some special sealant must be applied? Does it matter, what time of year this fix is performed?

UPDATE Below are the images of cracks:

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1 Answer 1


Is it for cosmetics or is it a matter of sweeping/washing off and things go between the cracks. Finally reason makes a difference. In commercial construction we often use concrete caulk, that way it is the same color and shrinks and expands with weather conditions. Mortar may work but if there is any shifting I would not be surprised if it becomes loose and looks just as bad as before. There are products that help when applying thin layers of concrete/mortar to stick but that it usually for applying an 1/8-1/4 inch. When do that when we are about to stain concrete that was not recently poured.

Note: looking at the pics I would not advise mortar as it would be difficult to fill and stick.

The concrete caulk will fill the gaps and seal it properly. Again the benefit of the caulk is it will shrink and expand if there is minimal shifting, where mortar will not..

Here is a link to for the caulk at home depot. http://www.homedepot.com/p/Red-Devil-10-1-oz-Masonry-and-Concrete-Repair-Caulk-0646/202261765

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  • With A link to the type of calking would get a plus from me. Because right now your answer is more of a comment.
    – Ed Beal
    Sep 5, 2016 at 9:36
  • @norcal johnny, thanks for comment. I'm planning to replace carpet in the basement, with concrete flooring. Articles and how-to videos recommend to seal cracks before placing pads and carpet. So I think it is not just for cosmetic purposes, but to prevent moisture etc. penetrate in the basement.
    – Mark
    Sep 5, 2016 at 13:26
  • @EdBeal, thank you for the suggestion. Please see updated answer. Sep 5, 2016 at 23:19
  • Much better + as this is a good answer.
    – Ed Beal
    Sep 5, 2016 at 23:32

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