Foundation defects include settlement, walls pushed out of line, and water moving through the foundation. University of Minnesota Extension says concrete and block foundations usually develop some cracks, and hairline shrinkage cracks are usually cosmetic. Horizontal cracks, wide cracks, and signs of movement such as sloping floors or out-of-square doors call for a professional evaluation.
Last reviewed: September 2026. Sources are listed at the end of this page.
Which foundation cracks are serious?
Horizontal cracks are the most serious sign, according to an article in the ASHI Reporter, the journal of the American Society of Home Inspectors (ASHI).[1]
| Crack type | What it usually means |
|---|---|
| Hairline vertical crack | Often simple shrinkage. Usually cosmetic.[1] |
| Horizontal crack | The wall has moved sideways. Always take it seriously.[1] |
| Stair-step crack in a block wall | Alone, not a major concern. Wide cracks, or several cracks together, point to a problem.[1] |
| Settlement crack | The footing has dropped or tipped. Typically wider at the top than at the bottom.[1] |
How wide is too wide for a foundation crack?
There is no single code threshold. Two inspector-association guidelines give different numbers, so treat them as rules of thumb.
- ASHI Reporter (Tom Feiza, 2007): any movement over 1/2 inch signals a possibly serious problem. A horizontal crack over 1/8 inch wide, with 1/2 inch or more of sideways wall movement, needs to be addressed.[1]
- InterNACHI (Keith Swift): cracks under 1/4 inch with no significant vertical or horizontal displacement are not considered a structural threat.[2]
The ASHI figure is the lower one. InterNACHI (the International Association of Certified Home Inspectors) also lists doors out of square and sloping floors as warning signs. A drop of more than 1 inch over 20 feet warrants a closer look.[2]
How does water damage a foundation?
Water that collects against a foundation builds pressure and pushes through any joint or crack. Building Science Corporation (BSC) calls this hydrostatic pressure.[3] BSC’s main controls are:[3]
- Gutters and downspouts that send water away from the house
- Ground graded away from the foundation
- Free-draining backfill or drainage board
- A footing drain to daylight or a sump
Signs of basement moisture include efflorescence (white mineral deposits), spalling concrete or masonry, a ring of dampness at the base of block walls, and standing water.[5] BSC says efflorescence shows moisture is moving through the foundation.[3]
How should the ground slope away from your house?
Both the ground and the downspouts should carry water away from the walls. The sources give different distances.
| Source | Grade and landscaping | Downspout discharge |
|---|---|---|
| Building America Solution Center (BASC) | At least 0.5 inch per foot for 10 feet on permeable ground, about 6 inches over 10 feet[4] | At least 5 feet from the foundation, or to an underground catchment at least 10 feet away[6] |
| University of Minnesota Extension | At least 1 inch per foot for at least 6 feet[5] | At least 4 feet beyond the wall, with one downspout per 50 feet of eave[5] |
| Colorado homeowner guide SP-11 (1978) | Keep irrigation and landscaping at least 5 feet from the foundation[8] | At least 10 feet from the building[8] |
According to BASC, the IRC (International Residential Code) requires hard surfaces within 10 feet of the house to slope 2 percent away. A driveway sloped toward the house is a common error.[4]
What are expansive soils?
Expansive soils are clays that swell when wet and shrink when dry. The Colorado Geological Survey (CGS) says they can expand up to 20 percent by volume and push with up to 30,000 pounds per square foot. CGS says national losses run into the billions of dollars.[7] Water ponding near the foundation and irrigated plantings next to it make the problem worse.[7]
The Colorado guide SP-11 says to look for cracks in basement and garage floors, driveways, sidewalks, and walls near door and window corners.[8]
Can framing cuts weaken the structure?
Yes. Notches and holes cut too large or in the wrong place reduce a joist’s or stud’s strength. InterNACHI summarizes the IRC limits for solid-lumber floor joists and studs:[9][10]
- Joist end notches up to one-quarter of the joist depth. No notches in the middle third of the span. Notches in the outer thirds up to one-sixth of the depth. Bored holes up to one-third of the depth.
- Bearing studs notched up to 25 percent of their depth, non-bearing studs up to 40 percent.
- Holes in bearing studs up to 60 percent of stud depth, with the stud doubled if the hole exceeds 40 percent. Holes stay at least 5/8 inch from the edge.
When should you call an engineer?
Call an engineer when you see serious settlement or active movement. The ASHI Reporter author says serious settlement may need soil testing and a special pier design.[1] The InterNACHI author says only a geologist or geotechnical engineer can predict further movement.[2] SP-11 advises consulting a professional engineer or home inspection consultant if you suspect significant damage.[8] See how to document a construction defect.
This page is general information, not engineering advice. Have a licensed professional engineer or qualified inspector evaluate your home.
Related guides
- Water intrusion and building envelope defects
- How to document a construction defect
- New-home builder warranties and structural coverage
- New-construction and pre-drywall inspections
- What a home inspection covers
Sources
- Tom Feiza, ASHI Reporter, “Basement Cracks and Leaks,” March 1, 2007.
- Keith Swift, InterNACHI, “Avoiding Litigation: Foundations,” no date shown.
- Kohta Ueno and Joseph Lstiburek, Building Science Corporation, “BA-1015: Bulk Water Control Methods for Foundations,” January 10, 2011.
- U.S. Department of Energy, Building America Solution Center, “Final Grade Slopes Away from Foundation,” last updated September 30, 2020.
- University of Minnesota Extension, “Moisture in basements: causes and solutions,” no date shown.
- U.S. Department of Energy, Building America Solution Center, “Gutters and Downspouts,” last updated September 26, 2021.
- Colorado Geological Survey, “Expansive Soil and Rock,” last modified December 5, 2024.
- W.G. Holtz and S.S. Hart, “Home Construction on Shrinking and Swelling Soils,” Special Publication 11, October 1978, hosted by the Colorado Geological Survey.
- InterNACHI Inspection Gallery, “Cutting, Notching, and Bored Holes in Floor Joist,” no date shown.
- InterNACHI Inspection Gallery, “Notching and Bored Holes at Exterior and Bearing Stud Walls,” no date shown.