Why do cracks open and close with the seasons?

Reviewed by Preston, Oklahoma foundation repair consultant · Updated 2026-10-14

In short: A crack that widens in the dry months and tightens again in the wet months is the classic sign of soil moisture driving foundation movement. On Oklahoma's expansive clay, the soil shrinks as it dries and swells as it rewets, and the house rides that cycle. Tracking the crack through a full year shows the pattern and its size.

Why do cracks open and close?

Expansive clay swells when it gets wet and shrinks when it dries, creating a repeating cycle of movement in the upper soil ². The zone of seasonal moisture change can extend from 3 to 40 feet deep depending on the site ². Because the edges, corners and areas near trees dry and rewet differently from the middle of the house, the movement is uneven, and uneven movement is what cracks walls, brick and slabs.

Texas monitoring of houses on expansive clay found average out-of-levelness growing from about 2-1/4 inches to 3-3/4 inches as the growing season progressed, with partial recovery when winter dormancy, rain and lower evaporation returned moisture to the soil ¹. Droughts during the growing season made settlement worse, and above-normal rainfall slowed it ¹. UK guidance likewise notes that soil shrinkage typically peaks in late summer ³.

What is Oklahoma's seasonal cycle?

More than 75% of Oklahoma has bedrock that can produce expansive soils, including clay-rich shales that can swell to 1.5 to 2 times their dry volume when wet ⁶. Soil moisture drops faster during hot, dry periods than during cool, wet ones ⁴. The Oklahoma Mesonet measures soil moisture at depths of 5, 25, 60 and 75 centimeters (about 2 to 30 inches) at stations covering all 77 counties ⁵, so readings from a nearby station can be lined up with crack measurements. See Mesonet for foundation pros and seasonal movement calendar.

What mechanisms produce it?

Engineering guidance on expansive soil notes that lack of watering in drought, which dries the clay, can be more damaging than overwatering, and that the goal is steady soil moisture ⁷.

How do you track a seasonal crack?

1. Mark the ends of the crack and two or three measuring points along it.
2. Measure width at the same points with a crack gauge or ruler, or install a crack monitor across it.
3. Photograph each point with a scale in view.
4. Record readings every month or two for at least 12 months.
5. Note rainfall, drought and watering changes alongside each reading; the U.S. Drought Monitor and Mesonet data give context.

A plot of width against date shows whether the crack follows the seasons, is steadily growing, or is stable. Seasonal cracks that also grow larger each year point to ongoing net movement.

What does it rule in and out?

Seasonal opening and closing points toward moisture-driven soil movement. It argues against causes that happen once, such as a single earthquake or impact, which tend to leave fresh, clean-edged cracks that do not cycle; see fresh, clean-edged cracks appearing suddenly. It also differs from truss uplift, which opens ceiling-to-wall joints in winter rather than in late summer.

What are the next steps?

Plot the cracks on an elevation survey, compare them with the distress pattern library, and use the symptom matrix.

Related

• Shrink-swell and active zone
• Drought and wet cycles
• Perimeter drying settlement (edge drop)
• Monitoring program
• Drought and wet years data