The First Three Things to Do About a Crack

Finding a crack is unsettling, and the natural response is to search for photographs that look like it. That produces anxiety rather than information, because appearance is the least diagnostic thing about a crack.

Here are three things that cost nothing, take about an hour in total, and make every subsequent conversation dramatically better.

1. Document it, with scale and a date

Photographs without scale are close to useless to somebody who was not standing there. Do it properly:

• A wide shot showing where the crack sits on the wall and how it relates to windows, doors, and corners. Position carries information: cracking near a corner or running out from an opening means something different from cracking in the middle of a blank wall.
• A close shot with a coin, a ruler, or a tape measure in frame beside the crack.
• A measurement of the widest point, ideally in millimetres, and a note on whether the width changes along its length.
• A pencil mark across each end of the crack with the date beside it. This takes ten seconds and it means any extension over the next year is immediately obvious.

Do this for every crack you can find, including the ones you think are nothing. The pattern across a house is more informative than any single crack, and the ones you dismiss are sometimes the ones that establish the mechanism.

2. Check the floor and the walls

Two five-minute tests that narrow the field enormously.

The floor. Put a marble on the floor in each affected room and see whether it runs, and which way. Then run a long level or a straight board across the same floor. What you are looking for is direction: a floor sloping toward an exterior wall or a corner points at settlement, while a floor dipping toward the middle of the house usually points at the support system in the crawl space, which is a much cheaper problem.

The walls. Hold a plumb line or a long level vertically against the foundation wall. A wall that is out of plumb, leaning inward, is being pushed by soil pressure rather than settling. That distinction decides the entire repair, because piers address downward movement and do nothing whatsoever for a wall under lateral load.

Between those two tests you have usually separated the three main possibilities before spending a penny.

3. Walk the outside in heavy rain

Not afterwards, during. Ten minutes in the wet beats an hour of dry-weather reasoning.

What to watch:

• Where water runs across the ground, as opposed to where you assume it runs
• Every downspout: where it discharges, how far from the wall, and where the water goes from there
• Whether the ground falls away from the house on all four elevations, or whether a bed, path, or patio has quietly reversed the grade
• Anything uphill delivering water toward the house: a slope, a neighbouring driveway, a blocked swale, or a spot where water emerges from the ground after rain

Water is somewhere in the history of nearly every foundation problem in this county, and roof discharge is the single largest input. An inch of rain on a modest roof produces well over a thousand gallons, and it all arrives at a handful of downspouts. Against annual rainfall of 55.92 inches at the Murfreesboro station in NOAA’s 1991 to 2020 normals, a downspout dumping at the corner of the house is a substantial, repeated event.

What not to do yet

Do not fill the crack. Filling it removes the evidence and, if the movement is ongoing, buys a season. There is no urgency to seal a crack that is not letting water in.

Do not call three repair companies for three opinions. Three contractors quoting off three different diagnoses produce three non-comparable numbers and a great deal of confusion. Either establish a cause first, or get one assessment and a second opinion on that assessment.

Do not panic about width alone. Mechanism outranks size. A 1 mm horizontal crack across the mid-height of a wall matters more than a 4 mm vertical shrinkage crack, and the vertical one is far more common.

When not to wait

Some things do not need a season of observation. Call sooner if a foundation wall is visibly leaning inward, if there is a horizontal crack across mid-height, if water is actively entering, if a door has gone from catching to not closing within a few months, or if anything has changed measurably in the past year.

Otherwise, doing these three things and looking again after the next wet and dry cycle is a perfectly sensible first step, and it means the conversation you eventually have starts from evidence rather than from worry.

Further detail in the crack reading guide and settlement or soil pressure.