What is EXCESSIVE? In short – any crack that makes you say “Holy Cow that’s a big crack” would be excessive. In more general terms – if you can stick a quarter into the crack that may be excessive – but certainly 2 quarters.
1/8″ (0.125) would be a good benchmark for concern – and 1/4″ (.25) would definitely fall into excessive for foundation settlement or foundation failure concerns.
How can you tell if your crack is just a shrinkage crack or stress crack? Several factors can help determine:
- Size – concrete is great in compression (standing or driving on it) – but not great in tension (pulling on it) – especially while curing. So in a basement or garage slab you can get cracking when there are limited control joints (joints that are cut or left to allow for shrinkage). So the larger the slab the more likely you are to have some shrinkage as the concrete dries. i.e. – cotton t-shirt the first time they are washed and dried. Use the quarter as a good homeowner guide.
- Displacement – displacement is when one side of the concrete crack is higher or lower than the other. Anytime a slab or wall has displacement there are other forces that could be acting on the wall or slab that would cause cracking and be a cause for concern.
- Location – yes – even in concrete cracks – location matters. If you have a crack near a corner of a basement or along a long stretch of wall then this is more likely due to shrinkage than foundation failure.
If you have a crack and trying to figure out if it’s a foundation problem or just a shrinkage crack – call and expert – a licensed structural engineer. While many foundation repair contractors know the difference between a shrinkage crack and foundation failure – a Structural Engineer is the only one who can write a letter or make the official call on these types of issues. The foundation repair contractor can only give you an opinion – and really should stick to giving proposals – not opinions on structural integrity.