Serving Madison and nearby areas
A horizontal crack in a basement wall in Madison, WI usually means soil pressure is pushing the wall in, and a free inspection tells you whether it is moving and what it takes to hold it.
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Need help sooner? Call (608) 719-3321.
Much of Madison sits between two lakes on filled marsh, with a water table close to the surface. Wet, silty glacier soil freezes several feet deep each winter and pushes on basement walls, and many homes near the isthmus and campus have stone or block basements close to 100 years old.
Typical published ranges for Madison. The contractor's written estimate is the price, and the inspection is free.
| Work | Typical range |
|---|---|
| Inspection and written estimate | Free |
| Crack sealing or injectionOnly after the wall is stable | $200 to $1,000 |
| Wall anchor, installed | $400 to $700per anchor |
| Bowing wall repair, typical range | $4,000 to $15,000 |
Most cracks in a basement are thin lines that run up and down. They come from concrete shrinking as it dries, and most are harmless. A horizontal crack runs the other way, side to side, and it has a different cause. Something outside is pushing on the wall.
In Madison, that push almost always comes from wet soil and frost. This page is about that one crack: how to read it, why it forms, and what it takes to stop it.
A long crack along one mortar line
On a block wall it follows a single row, often across most of the wall.
It sits a few rows below the ground line
Usually two to four rows of block down from the top, not near the floor.
One side sticks out
Run your hand across it. If the lower block sits out past the upper block, or the other way, the wall has shifted.
Damp or white powder along the line
Water uses the crack as a path in.
Stair-step cracks at the ends
The horizontal line often turns into zig-zag cracks near the corners.
A bow above or below it
The wall bends in at the crack line.
Frost. Wisconsin's home code asks for footings at least 48 inches below grade because frost goes deep here. In February 2014, Madison Water Utility reported frost 4 to 5 feet down. Wet soil swells as it freezes and pushes sideways. The upper rows of a block wall have the least weight on top to hold them, so they give first.
Water in the soil. The City of Madison says many older neighborhoods were built on filled wetlands, and that rising rain and snow have pushed ground water up into conflict with basements. Soil that cannot drain builds water pressure against the wall. Repair crews note that cracks from this kind of pressure often form part way up the wall, where the push is strongest.
Clay-rich soil. USDA describes the Dodge soil of Dane County as silt over glacial till, with a subsoil that is 25 to 32 percent clay. Soil like that holds water against the wall longer after rain and snowmelt.
Block construction. A block wall is many small units held by mortar joints. Each joint is a weak line, so pressure shows up as a long crack along one of them. About 1 in 3 Madison housing units was built between 1950 and 1979, per Census data, so a lot of Madison basements are now 45 to 75 years into this yearly cycle.
Probably stable if the crack is hairline, flat (both sides line up), dry, and has not changed in a year or more. Mark the ends and the widest point with a pencil and the date, and check after the next thaw.
Have it checked soon if the crack is wider than a coin edge, leaks, or has white powder along it.
Call now if one side sticks out past the other, if the wall bows at the crack, or if the crack grew since last season. A wall that is moving keeps moving each winter.
A horizontal crack is fixed in two steps. First the wall gets held so it stops moving. Then the crack and the water get dealt with.
Hold the wall
Wall anchors tied to the yard, carbon fiber straps glued to the wall, or steel braces from floor to framing. The choice depends on how far the wall moved and how much room there is outside.
Relieve the water
Downspouts carried well away, soil sloped away from the house, and on wet lots an inside drain to a sump pump.
Seal the crack
Once the wall is stable, the crack can be filled so it stops leaking.
Rebuild if needed
If blocks have slid far or broken through, that section may need to be dug out and rebuilt.
Sealing a moving crack without holding the wall is the most common wasted spend. The filler cracks again by next spring.
Crack sealing or injection runs about $200 to $1,000 per published cost guides. Wall anchors run about $400 to $700 each. A full bowing wall repair is often $4,000 to $15,000. These are typical ranges, not quotes. If the crack turns out to be stable, your price may be just the sealing.
It is the crack type to take most seriously, because it usually comes from soil pushing in, not from concrete drying. A thin one that has not changed in years may be stable. Have it checked once so you know which kind you have.
Filling it can slow water, but it does not stop the wall from moving. If the wall is being pushed, the crack opens again and the filler pops out. Bracing comes first, sealing second.
That is about where frozen soil and wet soil push hardest on a block wall. In Madison, frost can go 4 to 5 feet deep in a cold winter, so the upper rows of block take the sideways push.
Often, yes. Wet soil swells as it freezes. Many owners first see the crack, or see it widen, in late winter or spring after the thaw.
Any crack can let in radon. Public Health Madison and Dane County reports about half of homes tested in the county had high levels. A test kit is cheap and worth doing.
Call (608) 719-3321 or send the short form. A local crew will call you back, check the wall, and give you a written price. The inspection is free.
