How do I fix a concrete crack between two slabs?

expert EXPERT April 26, 2007

There is very little you can do to stop it from happening. The two slabs were poured at separate times, and therewill undoubtedly bedifferential settling between the two slabs. Even if it's minor, this will likely continue. Therefore, you could patch the crack by chipping it out and patching the crack. (They make special concrete mixes for patching. The material is designed to shrink less than normal concrete so that it doesn't create hairline cracks as it sets.) See the links below for additional information. Alternatively, and this depends on the shape and size of the existing crack, it may be better to saw cut the concrete to create a straight intentional joint between the two slabs. If done properly, future settling will occur at the saw cut, which will act as a control joint. If the crack wanders just slightly, you could consider two saw cuts very close to one another (less than an inch). The concrete between the two could be chipped out and replaced with expansion joint material andcaulking, designed for this purpose. Any future movement will be absorbed by the caulking, and no future repairs would be required.