What Expansive Clay Actually Does
I grew up with normal dirt. Dig a hole, fill it back in, done. Mike's soil is different. It has a personality. And that personality is angry.
The Swelling and Shrinking
The clay in Mike's yard contains minerals that absorb water into their molecular structure. When wet, the clay expands. When dry, it shrinks. Not a little bit. We're talking 10% volume change or more.
Mike demonstrated this for me. He had a clay sample from his yard, dried out in a jar. He added water. Over a few hours, I watched it expand until it cracked the jar. That's what's happening under his house, except the jar is his foundation.
The Forces Involved
Expanding clay can exert thousands of pounds of pressure per square foot. Mike's foundation guy told him that swelling clay can lift a house. Literally. The center of his slab can rise half an inch or more during a wet spring.
Then during drought, the clay shrinks. The soil pulls away from the foundation edges. The center drops. The house settles unevenly. Different pressures in different directions at different times. The foundation is constantly stressed.
The Seasonal Cycle
Mike's house moves with the seasons. Wet spring: doors tight, some cracks close. Dry summer: doors stick, cracks open. Fall rains: some recovery. Winter: relatively stable. Repeat every year.
He's learned which doors to not fight in August. Which cracks to not worry about because they'll close in October. The house has a rhythm. Once you accept it, it's almost predictable.
The Drought Year
2022 was brutal in central Texas. Months without significant rain. Temperatures over 100 for weeks. Mike's clay shrank more than he'd ever seen.
What Happened to His House
The perimeter of his foundation dropped while the center stayed relatively stable. The edges of the slab were in contact with soil that lost moisture. The center was under the house, protected from evaporation.
This created a dome effect. The middle of the house was higher than the edges. You could literally see daylight under doors that used to seal tight. Cracks opened that he'd never seen before. One window frame racked enough that the glass cracked.
The Crack Pattern
Mike's cracks were distinctive. Diagonal cracks from corners, pointing toward the center. Cracks along the exterior walls where the slab had bent. A crack in the drywall upstairs that followed the outline of where a support beam was stressed.
The whole house was telling the story of what was happening underground if you knew how to read it.
The Repair Bill
Mike had a foundation company come out. Their diagnosis: differential settlement from soil shrinkage. The solution: mudjacking to lift the settled perimeter sections and level the slab.
They pumped material under the low edges of the foundation, raising them back toward level. Not perfect, but close. Total cost: $6,500.
Mike started watering his foundation religiously after that.
The Watering Thing
I thought Mike was kidding about watering his foundation. He wasn't. It's a real thing in clay country.
How It Works
The soaker hoses sit about 12-18 inches from the foundation, running the perimeter of the house. During dry periods, Mike runs them every other day for 30 minutes. Just enough to maintain some moisture in the clay without flooding.
The goal isn't to make the soil wet. It's to keep it consistently not-too-dry. Even moisture equals even support. Big moisture swings equal big movement.
The Cost-Benefit
Mike estimates he uses about $40-50 of water per month during drought. Over a 4-month dry spell, that's $200 in water. His repair was $6,500. The math is obvious.
He also noticed his doors work better. His cracks stay smaller. The house is more stable since he started the watering program. Not perfect, but better.
The Limits
Watering helps during drought. It doesn't help during flood. When heavy rains come, the clay swells regardless. Mike can't prevent that. He just manages the dry side of the equation.
And watering is management, not cure. The underlying soil is still expansive. It's still going to move. Watering just reduces how much and how fast.
Why My House Doesn't Have This Problem
I asked Mike why my house up north doesn't do any of this. He'd visited me and seen my basement cracks. But my house doesn't breathe with the seasons like his does.
Different Soil
My soil has some clay in it, but not the highly expansive kind. The minerals are different. My clay expands maybe 2-3% with moisture changes, not 10%+. It moves, but not dramatically.
The geology matters. Texas, Oklahoma, Louisiana, Colorado... these areas have the really aggressive clays. My part of the midwest just doesn't.
Different Climate
Mike gets drought conditions I never see. Weeks of 100+ degrees with no rain. The soil can dry out 8-10 feet deep. Then monsoon rains saturate it completely. The moisture swings are extreme.
My climate is more moderate. Yes, it gets dry sometimes, but not for as long or as intensely. The wet-dry cycle is gentler, so even if I had expansive clay, it wouldn't move as much.
Different Foundation
Mike has a slab foundation. No basement. The whole house sits directly on the clay and moves with it. My house has a basement with deep footings. There's more structure to resist movement, and the footings extend below the active zone where most moisture change happens.
Slab foundations on expansive clay are particularly vulnerable. Mike's house was basically designed to move with the soil. Whether that was intentional or not, I don't know.
What Mike Recommends for Clay Soil Homeowners
Mike's lived on expansive clay for 15 years now. Here's what he's learned.
Learn Your House's Rhythm
Track which doors stick when. Note which cracks open during which seasons. Get a feel for how your house moves. Then you'll know when something is outside the normal pattern and worth worrying about.
Keep Trees Away
Trees make clay soil problems worse. They suck moisture from the soil, causing localized shrinkage. Mike has zero trees within 30 feet of his foundation. His neighbor had a live oak removed after it caused $12,000 in foundation damage.
Manage the Moisture
Water during drought. Ensure drainage during wet periods. The goal is consistency. Big swings are the enemy. Anything you can do to moderate the moisture cycle helps.
Accept Some Movement
Mike's house will never be perfectly stable. That's just life on expansive clay. You learn to live with some seasonal crack changes, some door adjustments. Fighting it completely is expensive and probably futile.
The goal isn't zero movement. It's managing movement to prevent major damage.
Budget for Repairs
Mike puts money aside every year for eventual foundation work. He figures he'll need mudjacking or other repairs every 10-15 years. It's just part of owning a house on this soil. Better to plan for it than be surprised.