The Decision in One Sentence
Measure when something has changed, when several observations cluster, or when a decision depends on the answer. Document and wait when an observation is isolated and static.
That framing does more work than any checklist, because it separates the two situations that actually matter: change and consequence. Our foundation evaluation page covers what the measurement itself involves.
Triggers Worth Measuring
A crack has widened between dated checks. The most reliable trigger available. If you marked and dated the ends and the crack has run past them, something is moving.
Displacement has appeared. One side of a crack sitting proud of the other means the two sections have moved relative to each other, which is more significant than width alone.
A repaired crack has reopened. Filler that cracks again along the same line is telling you the movement is active.
Doors have worsened progressively. Not seasonally, which is humidity, but steadily across years. Particularly where the gap around the door tapers rather than staying parallel.
Floors have become noticeably uneven. Or an existing slope has become more pronounced.
Several observations cluster in one part of the house. Cracking at multiple openings on one elevation, plus a binding door at that end, plus a floor falling that way. The pattern is the signal.
Something changed suddenly. After a drought, after unusually heavy rain, after a large tree was removed, or after a plumbing issue.
Damp or warm floor areas, sewer odours, or unexplained water usage. These raise the plumbing question, which changes the sequence.
Our guide on common foundation warning signs covers each observation in more detail.
What Can Reasonably Wait
A single hairline crack with no displacement. Document it and check after a season.
Seasonal door sticking that reverses. Timber responding to humidity.
Fine cracking along drywall tape joints. Extremely common and usually seasonal.
Cracking in new construction during the first couple of years. Framing dries out and settles.
A slope that has been there as long as you have owned the house and has not changed. Document it, then leave it.
The response in every case is the same: mark, date, photograph with a scale, and compare after a wet season and a dry one. That comparison costs nothing and answers the question better than a survey taken today with nothing to compare it against.
Transaction Timing
Before listing. The stronger position for most sellers. You learn the answer on your own schedule, you can address anything found, and you hand a buyer documentation rather than a disclosure with no supporting evidence.
Before buying. Particularly where prior foundation work is disclosed, or where you observe cracking or uneven floors during a viewing. A general home inspection notes visible conditions; it does not usually produce an elevation profile.
During an option period. Workable but compressed. Scheduling, surveying, and producing findings takes time, and an option period with a running clock is a poor environment for a considered decision.
After closing. Sometimes the only realistic timing, and it still gives you a baseline for the years ahead.
A note on urgency
Foundation movement in expansive clay is generally a slow process measured across seasons and years, not days. Anyone creating urgency around a foundation decision is doing something other than assessing your property. Take the time to get two opinions and read both scopes.
The Value of a Baseline
This is the underrated case for measuring.
A single elevation survey tells you the current profile. Two surveys taken a year or more apart tell you whether the structure is moving, in which direction, and roughly how fast. The second question is the one homeowners actually want answered, and only the pair answers it.
If you are in expansive clay, planning to stay long term, and already slightly worried, a baseline survey is a reasonable thing to own. It converts future ambiguity into a comparison.
What Happens If You Wait
Honestly, in most cases, not much in the short term. Movement is slow and a stable observation is stable.
Where waiting costs something is when the movement is active and the cause is progressive: a plumbing leak continuing to saturate soil, drainage continuing to erode support, or a season of drought deepening an existing differential. In those cases the scope needed at the end of the delay may be larger than the scope needed at the start.
The way to tell the difference between the two situations is the dated comparison. Which brings it back to documenting properly and checking again, which is free.