Send roof water away from the house, slope the ground away from it, and water slowly only when the soil pulls away from the slab. The goal is steady moisture, not soaking.
Clay soil changes volume as its moisture changes, and the foundation moves with it. Texas A&M AgriLife says dry clay constricts and the foundation sinks, and wet clay expands and lifts it. Swings between dry and wet cause the most trouble.
Amarillo's climate makes swings likely. NOAA's 1991 to 2020 climate normals for Amarillo International Airport show 20.36 inches of annual precipitation. That is an average. A dry year or a wet year can sit far from it.
Local soil adds to the picture. USDA says the Pullman series was established in Potter County in 1929 and occurs across the Southern High Plains of western Texas. Its description says Pullman is clay-rich in the subsoil and develops cracks 5 millimeters or more wide when dry.
The Texas engineers' guidelines say near-uniform soil moisture around all sides of the foundation may help, with a caution against excessive watering.
Gutters and downspouts do the most. The ASCE guidelines say uncontrolled roof runoff can cause erosion and ponding near a house, and that downspouts should extend well past the edge of the foundation and the edge of planting beds, into well-drained areas.
Ground slope matters too. For soil and planting areas next to the house, the guidelines suggest a slope of at least 5 percent, which is 6 inches of drop over 10 feet, for the first 5 feet all around where practical. Where grading cannot fix drainage, they describe solid pipe drains that carry water to an outlet. They say downspouts should not be connected to perforated-pipe subsurface drains. For groundwater, they describe perforated pipe in a gravel-filled trench, sloped at least 0.5 percent to an outlet, with cleanouts for maintenance.
Plants can help and trees can hurt. AgriLife says plants around a foundation hold soil and shade it so moisture does not evaporate as fast. It also says a 2 to 4 inch layer of mulch in planting beds holds moisture, but mulch should not be piled against the foundation because it can encourage termites.
The ASCE guidelines say trees or large shrubs near a foundation may cause soil shrinkage under it. Removing a tree can stop shrinkage, but it can also cause upheaval as moisture returns, especially if the tree is older than the house. Root barriers and periodic root pruning may reduce the effect, though the guidelines say barriers are generally less effective than removal.
Water when you see a gap between the soil and the foundation. AgriLife says to walk the house and check, and to pull back plants or mulch if you need to see the soil. If there is no gap, soil moisture is fine.
To water, AgriLife describes a soaker hose or drip line 8 to 18 inches from the foundation, a backflow preventer on the faucet, low pressure and a timer. It says not to water directly in a crack.
Call a Texas licensed engineer if cracks keep growing after drainage and watering are in order. Call a plumber or the city if you see water pooling near the slab with no obvious source.
The ASCE guidelines say well past the edge of the foundation and past the edge of abutting planting beds, into well-drained areas. They do not set one distance for every lot.
The guidelines suggest at least 5 percent, or 6 inches of drop in 10 feet, for the first 5 feet around the house where practical.
No. AgriLife says to keep a 2 to 4 inch layer in planting beds, but not to cover the foundation with mulch because it may encourage termites.
They may. The ASCE guidelines say vertical or horizontal moisture barriers may be effective against moisture migration under the foundation. They are a design decision for an engineer.
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