Direction Questions
What the crack direction tells you.
What do vertical cracks mean?
Vertical cracks are usually shrinkage cracks from when the concrete cured. They're the most common and typically least concerning type. Almost every poured concrete foundation has them.
My four basement cracks are all vertical. All harmless. Been there since 1978.
What do horizontal cracks mean?
Horizontal cracks indicate lateral pressure pushing against the wall, usually from soil outside. These are more concerning than vertical cracks because they can indicate wall failure beginning.
Gary's horizontal crack was the warning sign that his wall was bowing. Horizontal cracks deserve attention.
What do diagonal cracks mean?
Diagonal cracks often indicate settlement. One part of the foundation is sinking more than another, creating shear stress that cracks diagonally. Can also form from stress concentrations near windows or corners.
What are stair-step cracks?
Stair-step cracks follow the mortar joints in block foundations. They indicate diagonal stress but can't cut through the blocks themselves, so they follow the weaker mortar lines. Common in block walls under stress.
Width Questions
What crack width tells you.
How wide is too wide?
No hard cutoff, but: Hairline cracks you can barely feel are rarely concerning. Cracks you can fit a coin edge into deserve monitoring. Cracks you can fit a quarter into warrant professional evaluation.
My widest crack is about 1/8 inch. Been exactly that width for years. Not a concern.
Does crack width indicate severity?
Somewhat, but direction matters more. A 1/4 inch vertical crack might be fine. A 1/8 inch horizontal crack might be serious. Width plus direction plus change over time gives you the full picture.
What if one side is offset from the other?
If one side of a crack sticks out further than the other, that's displacement. The wall isn't just cracked; it's moved. This is more serious than a simple width measurement and warrants professional evaluation.
Location Questions
What crack location tells you.
Are cracks near windows normal?
Very normal. Windows create stress concentrations. The wall wants to crack somewhere, and window corners are natural starting points. Most window-area cracks are shrinkage, not structural.
My longest crack starts at a window corner. Textbook shrinkage according to the engineer.
What about cracks in corners?
Corner cracks can indicate settling or movement where two walls meet. Vertical corner cracks are often shrinkage. Diagonal or horizontal corner cracks might indicate differential movement.
Why would cracks appear in the middle of a wall?
Unusual but not impossible. Could be shrinkage if the wall was poured in sections. Could indicate a void in the soil behind the wall. Could be a stress point from uneven load above.
Center-wall cracks are worth more attention than corner or window cracks simply because they're less typical.
What if I see cracks upstairs too?
Foundation movement can transfer upstairs. Drywall cracks near doors and windows, especially diagonal ones, sometimes indicate foundation movement. Or they could be normal settling of the frame. Look for patterns.
Pattern Questions
What patterns of cracks mean.
Is one crack worse than multiple cracks?
Not necessarily. Multiple random shrinkage cracks are fine. One horizontal crack with wall bowing is serious. Pattern and behavior matter more than count.
What does a web or spider pattern mean?
Multiple intersecting cracks in a pattern sometimes indicate impact damage or unusual stress concentration. Map cracking on the surface can be from improper curing. Usually cosmetic but worth investigation if extensive.