✓Frost on the top of the wallWisconsin's home code asks for footings at least 48 inches deep to get below the frost. In the hard winter of 2014, Madison Water Utility reported frost 4 to 5 feet down. That top band of soil freezes, swells and pushes in on the upper part of the wall, which is where block walls crack.cityofmadison.com
✓Heavy, wet soilThe Dodge soil, first described in Dane County, has a subsoil of 25 to 32 percent clay over glacial till, per USDA. Silt and clay hold water, and wet soil is heavy against a basement wall.soilseries.sc.egov.usda.gov
✓Old block and stoneAbout 1 in 4 Madison homes was built before 1960, per Census data, and many have block or stone basements. The Wisconsin Historical Society says old stone foundations can bow inward from water and tree roots.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
Wall anchor, installedUsually spaced about every 5 feet
A bowing basement wall is one of the most common foundation problems in Madison. It usually starts slow. A crack shows up along a mortar line in a block wall. Then the wall in the middle starts to lean in. One day you notice the wall is not straight anymore.
This is fixable, and it costs much less when you catch it early. A wall that has moved an inch can usually be held and pulled back. A wall that has moved a lot may have to be rebuilt.
Does this sound like your wall?
"There is a long crack along my block wall, a few rows down from the top."
"The wall looks bent in the middle."
"The top of the wall slid in past the bottom."
"The cracks in my block wall look like stairs at the corners."
"My old stone wall is bulging and the mortar is falling out."
"The crack got wider after this winter."
If any of these sound like your basement, a local crew can measure how far the wall has moved and tell you what it takes to fix it.
Why basement walls bow in Madison
Two forces push on your basement wall from the outside: wet soil and frost.
Wet soil is heavy. Much of Madison has silty, clay-rich glacier soil, and the water table near the lakes sits close to the surface. When the soil is soaked, it presses hard on the wall.
Then winter comes. The top few feet of soil freeze, and wet soil swells as it freezes. That swelling pushes in on the top part of the wall. Block walls are strong top to bottom but weak side to side, so they crack along a mortar line and bow in.
Old stone walls on the isthmus and near campus face the same push, plus age. Over the years, water washes out mortar, and the wall loosens.
How a local crew fixes it
Wall anchors
The crew drills a small hole through the wall and digs a small hole in the yard several feet out from the wall. A steel rod runs from the wall to a steel plate buried in firm soil. A plate on the inside of the wall and a nut hold it tight. Anchors are usually spaced about every 5 feet. Over time, the nuts can be tightened to pull the wall back.
Steel beams
Steel I-beams are set against the wall from floor to ceiling. They are bolted into the floor and fixed to the floor joists or the sill above. Beams hold the wall in place and can be adjusted. They are a good choice when there is no room in the yard for anchors, which is common on tight city lots.
Carbon fiber straps
Strong straps are glued to the wall with epoxy, every few feet. They are flat, so they work in finished basements. They hold a wall where it is but do not pull it back, so they suit walls that have not moved far.
Helical tiebacks
A steel shaft with screw plates is turned through the wall and out into the soil at an angle. It works like an anchor but needs no hole dug in the yard.
Rebuilding the wall
If the wall has moved too far, the crew digs out the outside, takes down the damaged part and rebuilds it. It costs the most and is the last choice.
Fix the push, too
Anchors and braces hold the wall. The water is what pushes it. Most Madison jobs pair a wall fix with longer downspouts, better grading and sometimes an inside drain. See basement waterproofing.
What it costs
Typical ranges are in the table on this page. The number of anchors or beams is the biggest thing that moves the price. A 20-foot wall with anchors every 5 feet needs about four. Your written estimate shows how many, where they go and what is included before any work starts. See the Madison cost guide for more.
Frequently asked questions
How do I know if my basement wall is bowing?
Look for a long sideways crack across a block wall, often a few rows down from the top. Hold a long level or a tight string against the wall. If the middle sits closer to you than the top and bottom, the wall is bowing in.
Can a bowing wall be pulled back straight?
Often part of the way. Wall anchors can be tightened a little at a time, usually in drier months, to bring the wall back. How far it goes depends on the wall and the soil. The first goal is to stop it moving.
Wall anchors, steel beams or carbon fiber straps?
Straps are glued to the wall and hold it where it is, so they suit walls that have not moved far. Steel beams bolt to the floor and joists and work when there is no room in the yard. Wall anchors reach out into the yard and can be tightened to pull the wall back.
My lot is small. Can I still get anchors?
Anchors need open yard outside the wall, clear of driveways, porches and the house next door. On tight isthmus lots that is not always there. Steel beams or straps inside the basement are the usual answer.
Will wall anchors tear up my yard?
A little. The crew digs a small hole in the yard for each anchor plate, then fills it back in. Most yards look normal again after the grass grows back.
How fast does a bowing wall get worse?
Some walls move a little each year. Others jump after a wet fall and a hard freeze. Once a wall bows past a certain point, bracing is no longer enough and the wall has to be rebuilt. That costs a lot more, so it pays to act early.
Do I need to fix the water too?
Usually yes. Wet soil is what freezes and pushes on the wall. Longer downspouts, better grading and an inside drain take away the push, so the anchors do not have to fight it every winter.
Can I use wall anchors on an old stone wall?
Sometimes, but stone walls are different. Old stone often needs new mortar, bracing or a partial rebuild instead. The inspector will look at how solid the stone and mortar are before choosing a fix.
Book your free wall inspection
A bowing wall does not fix itself, and every freeze can move it further. 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.