The short answer
Foundations on clay stay steadiest when the soil around them stays at about the same moisture all year and on all sides. The Texas Department of Licensing and Regulation lists the tools: drainage, plants, sprinkling, maintenance. Get rain away from the house fast, don’t let one side dry out while the other stays wet, and keep big trees’ roots from pulling water out from under the slab.
This is maintenance, not repair. The Foundation Performance Association says maintenance systems should not be considered a repair, although they help a foundation perform. They do matter after a repair, though: the same paper says improper drainage can cause continued movement of a repaired slab.
Grading and gutters
The ground right next to the house should fall away from it. The ASCE Texas guidelines recommend, where practicable, a minimum slope of 5 percent (6 inches in 10 feet) away from the foundation for the first stretch all around. Builders in parts of east Austin know the stakes: at Easton Park, builders and their foundation engineers asked for lots sloped no more than 2% because of the expansive clay.
- Downspouts: extend them well past the edge of the foundation, past beds, into ground that drains.
- Beds: edging and mulch can turn a flower bed into a basin that holds water against the slab. Grade the soil inside the bed away from the house too.
- Soil level: keep soil and mulch below the top of the slab so water and termites can’t get at the framing.
- Flatwork: patios and walks that tilt toward the house send water straight under it.
Call to schedule an inspection
French drains and drainage systems
Where the yard itself slopes toward the house, or water stands along one side after every storm, a drain may be needed:
| Fix | What it does | Typical cost | Source |
|---|---|---|---|
| French drain along one side | A gravel trench with perforated pipe that carries water away | $1,200–$4,500 | HomeGuide |
| Drainage system | Surface drains, buried pipe and outlets around more of the house | $2,800–$6,500 | Angi |
| Gutter and downspout extensions | Carry roof water past beds and away from the slab | Usually the cheapest fix; ask for a price | — |
A drain has to go somewhere. Ask where it outlets, and how that avoids sending water onto a neighbor’s lot or back toward your own foundation.
East side, west side
On the clay east of I-35, the main job is keeping moisture even: water off the slab in storms, and enough moisture in a drought that the edges don’t shrink away from the middle. On the limestone side of town, runoff is the bigger concern. Thin soil over rock sheds water fast, and on a sloping lot it can run straight into the uphill side of the house or soak fill placed on the downhill side. There, regrading and drains usually come before anything else.
Call to schedule an inspection
Trees and roots
Big trees take a lot of water out of clay. The ASCE Texas guidelines say trees or large shrubs near a foundation may cause soil shrinkage under the foundation, the classic cause of one corner dropping during a drought. Removing the tree isn’t always the answer: the same guidelines warn that removal may cause upheaval as the soil rewets, especially if the tree predates the house. An arborist and an engineer may both have a view before a large tree comes down.
Root barriers, buried panels that keep roots from reaching under the slab, are a maintenance measure rather than a repair.
Watering through a drought
Texas loses more water to evaporation than it gets in rain across most of the state; the 2007 State Water Plan put it simply: evaporation exceeds precipitation. In a long dry spell, the soil at the edge of a slab dries first and shrinks away. Steady, moderate watering of the soil band around the house can slow that. Too much does harm of its own: the FPA says continuously saturated soil is detrimental to a foundation and its repair piers, and ASCE Texas advises caution against excessive watering.
A few practical rules:
- Water evenly around the whole house, not just the side that cracked.
- Aim at the soil a short distance out from the slab, not into the gap against it.
- Water less, more often, rather than flooding it once.
- Stop when it rains, and check that you’re not creating mud.
Call to schedule an inspection
Austin Water’s rules
Watering has to fit the city’s restrictions. As of the most recent update we read, Austin is under Conservation Stage water use restrictions.
| For homes on Austin Water | Current rule |
|---|---|
| Hand-held hose or watering can | any time on any day |
| Hose-end sprinklers and drip irrigation | 2 days per week, on your assigned days |
| Automatic and manual irrigation systems | 1 day per week |
| Watering hours on assigned days | midnight to 10 a.m. or 7 p.m. to midnight |
| Soaker hoses on any day | Only for trees and vegetable gardens; foundations aren’t on the list |
| Penalty for breaking the rules | up to $1,000 per violation |
Stages change with lake levels, so check Austin Water’s watering-day page before setting a schedule. Cedar Park, Leander and Pflugerville run their own water systems with their own rules; we didn’t find foundation-specific watering guidance from any of them, so ask your utility.
Questions to ask about drainage work
- Where does the water go, and where does the drain outlet?
- Will the grading meet the slope the ASCE guidelines recommend next to the house?
- Does the work keep soil below the top of the slab?
- What happens to beds, trees and irrigation lines in the way?
- If you’re also getting piers, is the drainage part of the same plan and warranty?