When is a foundation crack serious?

A crack is a line you can see. Seriousness is whether it is growing, and whether the house moved with it.

What a stair-step often means

Mississippi Geological Survey Circular 1 says Yazoo clay swells when it takes on water and shrinks when it dries, and that this movement cracks foundations in the Jackson belt. A stair-step in brick or block is the pattern that often shows that kind of movement.

The USGS swelling-clays map shows the same mineral family is common across large parts of the South and the Plains. Yazoo clay under Jackson houses is the local page for that clay.

What you can watch

A hairline at a corner that does not grow, and that does not move a door or a floor, can often be watched. Mark the ends and the date. Come back after the next dry spell or the next hard rain.

The Colorado Geological Survey swelling-soils guide says damage may occur slowly, and that houses on the same street can be affected at different times. Watching is how you see that.

What needs a closer look

Get a closer look if the crack steps, widens, a door misses the latch, a floor slopes, or a wall looks like it is bowing. What to do when the house is cracking or settling is the order. Do I need an engineer before a contractor? covers who should write the first opinion.