Houston foundation problems: what is normal, what is not, and when to call an engineer

Why Houston slabs move

Most of Houston is built on expansive clay. When the clay gets wet it swells, and when it dries it shrinks. A slab-on-grade foundation sits on top of that cycle. In a wet spring the edges of the slab rise. In a dry August they drop. A house with a big tree on one side, poor drainage on another, and a leaking drain line under the kitchen gets lifted and dropped unevenly, and that is what cracks drywall and sticks doors.

The movement is not a defect. It is the ground. The question is whether it is within the range the house can tolerate, and whether something is making one part move more than the rest.

What is normal

• Hairline cracks in drywall, especially over doors and windows, that open in summer and close in winter.
• Doors that stick in August and swing freely in January.
• Fine cracks in the slab surface or in brick mortar joints.
• A small gap between the slab and the soil at the edge in a drought.

These are worth watching, photographing with a date, and managing with drainage and watering. They are not by themselves a reason to buy piers.

What is not normal

• Cracks wider than about a quarter inch, or cracks that keep growing across seasons.
• Stair-step cracks running through brick, not just the mortar.
• Doors or windows that stay stuck year round, or frames that are visibly out of square.
• Separation between the brick and the frame at the roofline or at windows.
• Floors that slope enough to feel, or a floor elevation survey showing several inches of difference.
• Cracks in the slab you can see through flooring, or a floor that has heaved up in one spot.
• Plumbing problems that appeared along with the movement.

Any of these is a reason to call an engineer.

Drainage and watering come first

Most foundation movement in Houston is a moisture problem. Before anything else:

• Gutters on the whole house, with downspouts that carry water at least several feet from the slab.
• Grade sloping away from the house on every side.
• No beds, borders or planters that trap water against the slab.
• Large trees near the house drink from under the slab in a drought. An arborist or engineer can advise on root barriers or removal.
• In dry months, a soaker hose 12 to 18 inches from the slab on a timer, keeping the soil damp but not muddy, all the way around.

A house that is kept evenly damp moves less. Some engineers will tell you this is the whole fix.

Hire an independent engineer

A licensed professional engineer who does not sell foundation repair will inspect the house, take elevation readings, look at drainage and plumbing, and give you a written report that says whether the movement is structural, what is causing it, and what to do. This typically costs a few hundred dollars. The repair company’s free inspection is a sales call, and the person giving it is paid when you buy piers. Get the engineer’s report first, then get bids that follow it. If the repair company says the engineer is wrong, get a second engineer, not a second repair company.

Note that a general home inspector is not an engineer. An inspector can flag concerns. Only a PE can specify a repair.

Pier types used in Houston

Type	How it works	Notes
Pressed concrete pilings	Precast concrete cylinders pushed into the ground with the weight of the house, stacked until they reach resistance	The most common and least expensive method in Houston. Depth is limited by the house weight.
Steel piers	Steel pipe sections driven to refusal, then the slab is lifted onto them	Reach deeper than concrete, cost more, often preferred for heavier or badly moved houses
Bell-bottom (drilled) piers	A hole is drilled, widened at the bottom, and filled with concrete and rebar	The older method, needs curing time before lifting, less common for repairs now but still used

Houston has no shallow bedrock, so every pier relies on friction and resistance in deeper, more stable soil. Ask the engineer which type the report specifies and why, and ask the repair company what depth they reached at each pier.

After the lift

Lifting a slab moves everything attached to it, including the drain lines under it. A hydrostatic test on the drains and a pressure test on the supply, done by a licensed plumber after the lift, catches the break before it saturates the soil and starts the cycle again. Many repair warranties require this test. Also get an elevation survey after the work so you have a baseline.

Ask whether a City of Houston permit is required for the scope. Many repair companies pull one with the engineer’s letter. Confirm before work starts.

Warranties

Most Houston foundation companies offer a long or lifetime warranty that transfers to the next owner. Read what it covers. Usually it is an adjustment of the piers they installed if those piers move, not new piers in other areas, and not interior repairs. The warranty is only as good as the company’s continued existence. A company that has operated under the same name in Houston for a long time is worth more than a longer warranty from a newer one.