✓Water pushing from outsideCity staff say ground water flooding happens in filled wetlands, especially on the Madison isthmus, after many wet seasons. When the soil around a basement is soaked, water pushes into any crack it can find.cityofmadison.com
✓Frost every winterWisconsin's home code asks for footings at least 48 inches below grade to get under the frost, and Madison Water Utility reported frost 4 to 5 feet down in the winter of 2014. Soil that freezes and thaws pushes on walls and opens cracks.dsps.wi.gov
✓Old mortarThe Wisconsin Historical Society says old stone foundations show stair-step cracks and lose mortar when moisture works through them. In block and stone walls, cracks often follow the mortar lines.legacy.wisconsinhistory.org
What it costs
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 injection
$250 to $1,000per crack
Foundation crack repair, national
$200 to $1,000
Bowing wall repair, if the crack comes from a moving wall
Almost every basement in Madison has a crack somewhere. Most are not an emergency. But some cracks leak, some grow, and some are a sign the wall is moving. The hard part is telling which is which.
That is what the free inspection is for. A local crew looks at the crack, the wall around it, and the cause, then tells you if it needs a simple seal or a bigger fix.
What kind of crack do you have?
The type of crack tells a lot about what caused it.
Thin, straight up-and-down crack in a poured wall. Very common. Concrete shrinks as it cures. These often leak but rarely mean the wall is failing.
Crack that runs sideways across a block wall. This usually means soil and frost are pushing the wall in. It often comes with a bow. See wall anchors.
Stair-step crack along the mortar in a block or stone wall. Often settling at a corner or pressure on the wall. Worth a look.
Crack wider at the top than the bottom. A sign one part of the house is settling.
Crack where one side sticks out past the other. The wall has shifted. Have it checked soon.
Cracks in the basement floor. Often shrinkage, but water or soil movement can push them up.
Why cracks show up in Madison
Water and frost do most of the damage here. Madison has a high water table near the lakes and on the isthmus, and the soil holds a lot of silt and clay. Every winter, the top few feet freeze. Wet soil swells when it freezes, and that pushes on the wall. Every spring, snowmelt soaks the ground again. Over years, that cycle opens cracks and makes old ones longer.
Older homes have their own issues. Stone and block walls from the early 1900s lose mortar over time, and cracks follow the mortar lines.
How a local crew fixes cracks
Crack injection
For poured concrete walls, the crew sets small ports along the crack, seals the face, and pumps in a foam or epoxy. It fills the crack all the way through the wall. Foam flexes a little and is often used to stop leaks. Epoxy bonds the concrete back together and adds strength.
Repointing
For block and stone walls, the crew cleans out loose mortar and fills the joints with new mortar that matches the wall. Old stone walls need a soft mortar that fits them, not a hard modern mix.
Floor crack sealing
Floor cracks can be sealed with a flexible filler. If water comes up through the floor, an inside drain and sump pump are usually the better fix. See basement waterproofing.
Fixing what caused it
If the crack comes from a wall that is bowing or a corner that is sinking, sealing alone will not last. The wall is braced or the corner supported first, then the crack is sealed. See foundation repair.
Watch it before you call
If you are not sure your crack matters, start a simple log. Mark the ends with a pencil and write the date. Measure the width with a ruler. Take a photo. Check again in a month, and after the next big rain or freeze. If it grows, call. If it leaks, call. If you see a bow in the wall, call now.
What it costs
Typical ranges are in the table on this page. One crack is usually a small job. Many cracks, or a crack in a wall that is moving, cost more because the cause gets fixed too. See the Madison cost guide for more.
Frequently asked questions
Which foundation cracks should I worry about?
Cracks that grow, cracks wider than about a quarter inch, cracks where one side sticks out past the other, and long sideways cracks in block walls. Thin, straight up-and-down cracks in poured walls are common and often just need sealing if they leak.
How can I tell if a crack is growing?
Put a pencil mark at each end of the crack and write the date. Take a photo with a coin or ruler next to it. Check again in a month and after the next freeze or big rain.
Can I seal a basement crack myself?
You can patch the surface, but surface patches often pop loose when water pushes from outside. A crack injection fills the crack all the way through the wall. If the crack is part of a bowing wall, a patch only hides it.
Why does my crack only leak in spring?
Snowmelt and spring rain raise the water in the soil around your basement. In Madison, ground water can rise close to the surface after a wet season, and the crack becomes a path in.
Do foundation cracks let in radon?
They can. Public Health Madison and Dane County says radon gets in through small cracks in floors and walls, and about half of homes tested in the county had high levels. Sealing cracks helps, and a radon test tells you where you stand.
How long does crack injection take?
Most single-crack injections take a few hours. The material sets in about a day. Several cracks or a crack in a bowing wall may take longer.
Will a crack repair hold if the wall keeps moving?
Not for long. If the wall is still moving, the crack will open again. That is why the inspector checks the wall for bowing and the cause of the movement before sealing anything.
Get your crack checked for free
A crack that leaks this spring will leak again next spring. Call (608) 719-3321 or send the short form, and a local crew will call you back, usually the same day. The inspection is free, and you get the price in writing.