Bring your dated readings and photographs to any inspection: they shorten the conversation considerably
Homeowner guide · 15 minutes, then a few minutes each season
How to monitor a foundation crack: is it actually moving?
Almost every foundation has a crack. What matters is whether it is changing, and memory is a poor instrument for that.
Short answer
Mark both ends of the crack with a dated pencil line, mark a fixed measuring point across it, and record the width there with a crack gauge or calipers. Photograph it with a ruler in frame. Repeat every season and after any major weather event. Three or four dated readings across a year tell you far more than a single expert glance, and they are exactly what an inspector or engineer wants to see.
Safety first
Monitoring is for tracking a condition over time, not for deciding whether a wall is safe. A wall that is bowed, displaced or visibly changing needs assessment now. Watching it is not enough.
Before you start
What you need
- A pencil
- A crack gauge, calipers or a steel rule with fine graduations
- A camera or phone
- A notebook or a note on your phone
Step by step
8 steps.
- 01
Clean the surface. Brush away dust, cobwebs and any loose material around the crack so your marks sit on sound masonry and stay legible for months rather than smudging the first time someone brushes past.
- 02
Mark each end. Draw a short pencil line across the crack at each end and write the date beside it. If the crack later extends past your mark, that is unambiguous evidence of growth.
- 03
Establish a measuring point. Choose one spot along the crack, ideally the widest, and mark a line on each side perpendicular to it. Always measure at this same point, otherwise you end up comparing different places, not different times.
- 04
Record the width. Measure the gap at your marked point with a crack gauge or calipers and write it down with the date. A gauge taped over the crack gives the easiest repeatable reading.
- 05
Photograph with a scale. Take a photograph with a ruler or tape measure in frame beside the crack, and a second wider shot showing where on the wall it sits. Photographs without a scale are much harder to compare later.
- 06
Note the conditions. Record the date, the season and anything relevant: recent heavy rain, a spring thaw, a very dry spell. Some cracks open and close seasonally, and that pattern is itself informative.
- 07
Repeat each season. Take a new reading roughly every three months, and after any unusually wet period. Keep every reading, not only the latest. The trend is the finding.
- 08
Watch for the signals that change the answer. If the crack widens measurably, extends past your end marks, develops displacement so one side sits proud of the other, or starts passing water, stop monitoring and get it evaluated.
How to read the measurements
The point of monitoring is to replace a worry with a number. Measure the same spot the same way at fixed intervals, and keep the dates. Movement that reverses with the seasons is a different finding from movement that only goes one way.
If a crack is changing while you watch, do not wait for the next scheduled reading before getting it looked at.
| What the readings show | What it usually means | What to do |
|---|---|---|
| No change over several months | The crack is stable | Keep a yearly record and address any water |
| Opens in summer and closes in winter | Seasonal movement | Record the range and mention it at any inspection |
| Gets steadily wider | Ongoing movement | Have it evaluated |
| Offset between the two sides grows | Vertical displacement | Have it evaluated promptly |
After the check
What to do with the result
A stable, dry crack with no displacement across a year is a very different finding from a growing one
Horizontal cracks and bowing walls are not candidates for watchful waiting
Keep the record even after a repair, so you can tell whether the repair held
Common questions
How to Monitor a Foundation Crack
How much crack movement is too much?
There is no single number that applies to every wall, because it depends on the material, the pattern and whether displacement is developing. What is clear is that measurable growth over a year, extension past your marks, or one side moving out of plane relative to the other are all reasons to have it evaluated instead of watched further.
Is it normal for a crack to open and close with the seasons?
Some seasonal movement is common as soil moisture and temperature change through the year. That pattern, returning to roughly the same width each cycle, is different from a crack that grows and stays grown. Keeping readings across a full year is what lets you tell them apart.
Should I fill the crack while monitoring it?
Filling it removes your ability to measure and can hide continuing movement. If water is coming through and needs addressing sooner, note that the repair also ends the monitoring, and ask the contractor to record the width and pattern before sealing it.