The short answer
The ASCE Geo-Institute’s homeowner guide calls uniform soil moisture next to and under the foundation the single best thing you can do to reduce shrink-swell movement. The reason is simple: uniform changes in soil moisture are less damaging to a house than localized ones. A dry corner under a tree or a soggy bed by the back door is what bends a slab.
Drainage work doesn’t lift anything. The Foundation Performance Association says foundation maintenance systems should not be considered a repair. But it also warns that improper drainage can cause continued movement to the repaired slab, so on a house that’s been piered, drainage is what protects the repair.
Where water goes wrong around a house
| Problem | What it does | The fix |
|---|---|---|
| Downspouts emptying at the slab | Soaks one spot of clay every rain | Extend them past the beds into ground that drains |
| Flat or reversed grade | Water runs toward the house and ponds | Regrade so the soil falls away on every side |
| Beds with edging that traps water | Keeps the soil along one wall wet | Slope beds away; don’t dam them with edging |
| Sprinkler heads near the house | Leaks and overspray keep one side wet | Move heads and valves back from the foundation |
| Trees close to the house | Roots dry the clay under one corner | Prune, root barrier, or water evenly; get advice before removing |
| A leak under the slab | Feeds water to clay under the middle | Find and repair it, then re-check the floor |
The Texas Department of Licensing and Regulation lists the same levers in its bulletin on expansive soils (drainage, plants, sprinkling, maintenance) and says all of them help keep the soil’s water content steady.
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Grading: the slope away from the house
ASCE Texas recommends, where practicable, ground that slopes away from the foundation at a minimum of 5 percent (6 inches in 10 feet) for the first 10 feet. The Geo-Institute’s homeowner version is at least 3 inches of fall in 5 feet on all sides. Lots built to drain often lose that slope as beds, patios and fences get added, so a yard that drained well at closing may not now.
When adding soil, the Geo-Institute says to use clay, not sandy soil, compacted so it sheds water, and to keep the dirt line several inches below the top of the foundation.
Gutters and downspouts
Roof water lands on a small strip of ground. Without gutters, it falls along the drip line all around the house; with gutters, it all comes out of a few downspouts. ASCE Texas says downspouts should be extended well past the edge of the foundation and past any planting beds and into well-drained areas. The Geo-Institute puts a number on it: discharge at least 3 feet from the foundation, with splash blocks to stop erosion.
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French drains and surface drains
Where water still collects after grading, a drain carries it away. Two kinds do different jobs:
- Solid pipe surface drains collect water from inlets and downspouts and carry it to the street or a low point. ASCE Texas suggests them when grading alone can’t drain an area, with cleanouts for maintenance.
- French drains are perforated pipe in a gravel trench that catch water moving through the soil. ASCE Texas says downspouts and surface drains shouldn’t connect to them.
HomeGuide puts a French drain along one side of a house at $1,200–$4,500, and Angi puts a drainage system to address foundation problems at $2,800–$6,500. Ask what the system will do with the water once it’s collected; a drain that empties into the next flower bed moves the problem a few steps.
Soaker hoses and watering
In a long dry spell, the soil at the edge of a slab dries first and the edge drops. ASCE Texas says owners should be told that keeping near uniform soil moisture on all sides of the foundation may help, and in the same breath advises caution against excessive watering. The Geo-Institute’s drought advice is a soaker hose about 18 inches from the foundation, with more water on the south and west sides that bake in the afternoon sun.
City rules decide when you can run it. Plano lets residents water foundations up to two hours any day with a hand-held or soaker hose. Frisco allows hand-held hoses, soaker hoses and drip, no more than 2 hours per day. McKinney lets beds and trees be watered more often than the sprinkler schedule with hand-held hoses, soaker hoses or drip zones. The watering guide covers each city and how to tell when to stop.
Automatic perimeter watering systems are sold as foundation protection. The Foundation Performance Association lists their risks: over-watering can cause adverse movement, and dramatic foundation settlements could follow if a system the soil has come to depend on stops working.
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Trees and roots
Roots pull water from clay, and a big tree near a slab can dry the soil under one corner faster than any watering keeps up with. The Geo-Institute’s rule for planting is to keep trees farther from the house than their mature height. For trees already there, the options are pruning, a root barrier, or removal, and removal is the risky one: ASCE Texas warns it can lead to upheaval as the soil rewets. ASCE also suggests talking to an arborist before installing a root barrier, since cutting roots can harm the tree.
Leaks under the slab
A slow leak is a hidden water source under the middle of the house. The Geo-Institute’s advice is to monitor water bills and foundation behavior, hire a leak detection plumber, and confirm repairs with a pressure test. Fixr puts an average slab leak repair at $2,500. Texas homeowners policies may cover foundation damage from a sudden leak, which isn’t true of drought damage; the insurance guide explains the difference.
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What drainage work costs
| Item | Typical cost | Source |
|---|---|---|
| Drainage system to address foundation problems | $2,800–$6,500 | Angi |
| French drain along one side | $1,200–$4,500 | HomeGuide |
| Slab leak repair, average | $2,500 | Fixr |
Gutter extensions and splash blocks are a weekend job. Regrading, drains and leak repair are worth a written quote.
A yearly drainage check
The Geo-Institute recommends inspecting the area within 5 feet of all sides of the house once a year. A short list:
- Walk the house in a heavy rain and watch where water goes.
- Check that every downspout still has its extension and empties onto ground that drains.
- Look for low spots, ponding and soil washed against the slab.
- Check that sprinkler heads still point at the lawn, not the wall, and sit at least 5 feet from the foundation.
- Look at the brick and doors on the side with the biggest tree.
If you’re already seeing cracks or sticking doors, a contractor’s inspection will show whether the house has moved, and whether drainage alone is enough.