(Also see Concrete and Exterior Concrete Substrates)
Hairline cracks (very thin cracks) will often occur in new concrete slabs due to shrinking and are not typically a cause for concern. However, all existing cracks should be examined, as certain types of cracks can be a sign of a more serious issue. When examining existing cracks, there are three main things to look for:
1. Is the crack flat or is one side of the crack higher than another?
2. Is the crack short in its length or does it span from one outside wall to another?
3. Is the crack old and has it become wider over time?
If the crack is flat, short in length or is old and has not moved, the application of a crack-isolation membrane like MAPEI Mapelastic AquaDefense is recommended. However, if the crack is not flat, if it spans the length of the structure or if it has become wider over time, an inspection by an experienced professional engineer is recommended in order to determine appropriate repair procedures.