First and most important – ALL concrete cracks. That is the one guarantee that is certain with concrete. Even if you can’t see the cracks, they are still there. So which cracks are bad and which cracks aren’t? Typically a crack less than 1/8” wide can simply be ignored. Cracks between 1/8” and ¼” are usually nothing to worry about unless there is movement in the concrete. Make sure that there isn’t movement up/down, left/right, in/out between each side of the crack. If movement is noticed then it is possible that a more significant issue exists and warrants investigation. Cracks larger than ¼” warrant further investigation.
Cracks in foundation walls often cause homeowners additional concern. But these cracks are caused for the same reason as cracks in a driveway or garage floor. In general thin vertical cracks in a poured foundation wall are no concern. If the crack is wider than about ¼” or the wall shifts on either side it warrants further investigation. Horizontal cracks in a foundation wall deserve more scrutiny. A horizontal crack may indicate excess pressure on the exterior of the foundation wall.
Minor cracks in concrete are easily repaired by DIY home owners. And in our northern climate it is a good idea to fill exterior concrete cracks. Filling these cracks will help prevent water from entering the crack, freezing and causing more damage. Depending on the crack you can use caulk, concrete crack filler or hydraulic cement to fill the crack.
Remember, cracks in concrete are a fact of life and most concrete cracks are cosmetic. For wide cracks where there appears to be movement in the concrete further investigation is warranted.