Almost every home in Westchester has foundation cracks. Most are harmless. A few are not. The difference is not how long or how ugly the crack is — it is the direction, the width, and whether it is moving.
The quick read
| Crack type | Usual meaning | Concern level |
|---|---|---|
| Thin vertical (<1/8") | Normal curing shrinkage | Low — seal if it leaks |
| Wide vertical (>1/4") | Settlement | Moderate — monitor and measure |
| Diagonal from a corner | Differential settlement | Moderate — evaluate |
| Stair-step in block or stone | Uneven settlement | Moderate to high |
| Horizontal | Lateral soil pressure | High — evaluate now |
| Any crack with bowing | Wall is failing | High — evaluate now |
Vertical cracks
The most common and least worrying. Concrete shrinks as it cures and typically cracks vertically somewhere in the first two years. They often show up near the middle of a wall or beside a window opening.
- Under 1/8 inch and not growing: cosmetic. Seal it if water comes through — $500–$1,500 for injection.
- Over 1/4 inch, or wider at one end: that taper suggests one side is settling. Worth measuring over time.
Horizontal cracks — the one that matters
A horizontal crack running along a basement wall means soil is pushing the wall inward. It is not shrinkage. Common causes in Westchester: saturated soil after heavy rain, frost pressure, a hillside lot, or a driveway that drains toward the house.
Check for bowing: hold a straight edge or run a string line vertically against the wall. Any measurable inward deflection changes this from "get it looked at" to "get it looked at soon."
Act now if you see: a horizontal crack combined with visible bowing · a crack you can fit a coin into · a crack that has widened noticeably in one season · stair-step cracking plus doors and windows sticking upstairs · water pushing through under pressure. None of these are same-day emergencies, but none should wait a year either.
Stair-step cracks
These follow mortar joints in a diagonal staircase pattern and are typical in concrete block and in the rubble stone foundations common in Ossining, Tarrytown and Peekskill. They usually mean one part of the footing is settling more than another.
In old stone foundations, some stair-step cracking is historic and long since stable. The question is always the same: is it moving now?
Diagonal cracks
Typically start at a corner of a window or door opening and run at roughly 45 degrees. These indicate differential settlement — one section dropping relative to another. Common near additions, where new footings settle at a different rate than the original house.
Take a clear photo with a coin or tape measure next to the crack and send it to us. We will tell you honestly whether it needs attention.
📅 Free assessmentHow to monitor a crack yourself
Before spending money, gather evidence. This costs nothing and it is genuinely what an engineer wants to see:
- Draw a pencil line across each end of the crack and write the date.
- Measure the width at the widest point. A crack gauge card costs a few dollars; a coin works as a reference in photos (a US quarter is about 1/16" thick).
- Photograph it monthly, with the tape measure in frame, for six months — you want to capture at least one full wet season and one freeze.
- Note whether doors and windows above it start sticking.
A crack that has not moved in six months across a Westchester winter is very likely stable. That single fact can save you thousands in unnecessary work.
Signs elsewhere in the house
Foundation movement rarely stays in the basement. Look for:
- Doors and windows that suddenly stick or will not latch
- Sloping or bouncy floors
- Diagonal cracks in drywall above door and window corners
- Gaps opening between crown molding and ceiling
- Separation between a chimney or porch and the main house
Any two of these together with a growing foundation crack is a reason to bring in a structural engineer — roughly $600–$2,500, and worth it before you commit to any repair.
Related: foundation repair costs · basement waterproofing · water damage warning signs
Frequently Asked Questions
Usually not. Thin vertical cracks under 1/8 inch wide are the most common type and typically come from normal concrete curing shrinkage in the first few years. They may leak water, but they rarely indicate structural movement.
A horizontal crack means the wall is being pushed inward by soil pressure rather than simply shrinking. It indicates the wall is bending and losing capacity. Horizontal cracks should always be evaluated by a professional, and quickly if the wall also bows inward.
Stair-step cracks follow the mortar joints in a block or stone wall and usually indicate differential settlement — one part of the foundation is dropping faster than another. Narrow ones may be old and stable; ones wider than 1/4 inch or actively growing need evaluation.
Mark each end with a pencil line and the date, and measure the width. Photograph it monthly for six months. Movement over a season is the single most useful piece of information you can bring to a contractor or engineer.