Reading Foundation and Wall Cracks
Cracks are evidence, not a diagnosis. Their pattern narrows the possibilities; measurements confirm what is actually happening. Anyone willing to tell you what your foundation needs from a single photograph is selling, not evaluating.
Vertical cracks
Common in concrete and often related to shrinkage as the material cured. Narrow, non-displaced vertical cracks are frequently benign. A vertical crack that is wider at the top or bottom suggests one side is rotating, which is a different matter.
Horizontal cracks
In a basement or foundation wall, a horizontal crack usually indicates lateral pressure from saturated soil. This pattern deserves prompt evaluation, because the wall is being pushed rather than settling.
Stair-step cracks in brick or block
Cracking that follows the mortar joints in a stair-step pattern typically means one section of the wall is moving vertically relative to another. Direction of the step points toward the settling side.
Diagonal drywall cracks from openings
Door and window corners are stress concentrators. Diagonal cracks radiating from them indicate the frame is racking out of square, which happens when the floor beneath is no longer flat.
What to document before you call anyone
- Date and photograph each crack with a ruler or coin for scale
- Note whether the two sides are offset, or only separated
- Mark the ends with a pencil line so you can see if it lengthens
- Record whether doors stick in a particular season
- Note where downspouts discharge and where water stands after rain
Why measurements settle the question
An elevation survey across the floor shows how much the structure has actually moved and where. That is the difference between guessing at a crack and knowing the shape of the problem — and it is what a repair scope should be built on.
Document the crack over time, then get elevation readings. Pattern suggests; measurement confirms.