New cracks after dry weather: what to check

The ground beneath the valley floors around Huddersfield holds bands of shrinkable clay. During a long dry summer that clay loses moisture and contracts, pulling away from the underside of shallow footings. Homes built on this clay are more likely to show new cracks after dry weather than those sitting on the millstone grit higher up the hillsides.

You might notice hairline lines appearing inside, often running from the corners of windows or doors toward the ceiling. Outside, late summer cracks brickwork along mortar joints, sometimes stepping diagonally up a wall. This is clay soil shrinkage at work. The ground has lost volume because it dried out, so the footing settles slightly until rain returns.

Read more about the geology beneath local homes in our notes on [millstone grit and clay ground](/news/millstone-grit-and-clay-ground-under-huddersfield-homes). A specialist surveyor checks these conditions before recommending any repair.

Many people ask whether cracks that appear in summer close in winter. With shrinkable clay, they often do. Rain through autumn and winter rehydrates the soil, which swells back toward its original volume. The wall may settle back into place and the gap narrows or disappears entirely.

This pattern means the movement is seasonal rather than progressive. Seasonal cracks plaster walls inside tend to be thin, usually less than two millimetres wide, and follow the same path each year. They open in August or September and tighten by February.

But not every gap closes completely. If a crack widens beyond five millimetres, runs right through the wall, or fails to narrow when the ground gets wet again, something else may be happening. That is the point where asking a specialist firm for a [subsidence survey](/subsidence-survey-huddersfield) makes sense. Tracking movement over months tells you whether the ground is simply cycling with the seasons or dropping further each year. You can learn how to record changes yourself by [measuring a crack week by week](/what-you-can-see/measuring-a-crack).

A large tree close to a wall draws significant moisture from the ground. In a dry summer, tree roots drying soil foundations can exaggerate the normal shrinkage of clay. The area directly beneath the canopy dries faster and deeper than the rest of the garden, so one corner of a house may drop while the rest stays level.

Removing the tree seems like an obvious fix, but felling a mature tree near clay ground creates another problem. Without roots extracting water, the clay absorbs rainfall and swells. That heave pushes footings upward and causes a different kind of damage. Specialist firms consider root spread, species and soil type before advising on removal.

If you suspect a tree is involved, a [structural monitoring](/structural-monitoring-huddersfield) programme records exactly what the wall does month by month. The data shows whether the movement tracks with the seasons or follows a steady downward line.

It is tempting to fill and paint over a crack as soon as it appears. But if the ground is still moving, rigid filler will split again within weeks. Decorating over fresh filler hides the evidence a surveyor needs to read the movement.

Wait until the wetter months arrive and the wall has had time to settle back. If the crack closes fully, a flexible decorator's caulk handles the slight residual movement better than hard plaster. If it stays open, the cause needs identifying first.

Specialist firms carry out [crack repair](/crack-repair-huddersfield) only after establishing why the wall moved. Filling a gap without understanding the ground beneath it wastes time and money. For wider damage to masonry, look at what [stepped cracking in brickwork](/what-you-can-see/stepped-cracks-brickwork-huddersfield) indicates about the direction of movement.

Reporting every hairline crack to a buildings insurer can trigger a claims history that affects future premiums, even if the movement turns out to be harmless seasonal shrinkage. Most insurers expect homeowners to monitor small cracks through one full wet and dry cycle before making a report. Read more about how [buildings insurance covers subsidence](/what-you-can-see/subsidence-and-your-policy) and what policies typically require.

Watch the crack for at least three months. Mark the ends with a pencil and date them, or fix tell-tales across the gap. If the crack keeps widening past the autumn rains, or if doors begin sticking because frames have twisted, call in a specialist firm.

The difference between clay shrinkage and real subsidence needing underpinning comes down to direction and persistence. Seasonal movement goes back and forth. Progressive subsidence moves one way and accelerates. Where underpinning is needed, methods such as [mass concrete](/mass-concrete-underpinning-huddersfield) or [mini piled foundations](/mini-piled-underpinning-huddersfield) transfer the load below the shrinking clay layer.