Drainage & Soil Correction
Foundation Drainage Correction San Antonio, TX
Stop water from undermining your San Antonio foundation. Grading, French drains, and moisture plans for expansive clay soil.
Foundation drainage correction in San Antonio protects the slab from clay that swells when wet and shrinks in drought. Negative grade, clogged gutters, and flat ranchland lots funnel water to the footing line, the exact place expansive soil does the most damage. Drainage is not optional landscaping. It is how you keep a pier job from fighting the same puddle every spring.
Drainage alone cannot lift a slab that already dropped. It can slow damage, and it should sit in the same scope as slab repair when a corner is still wet. Soil science: expansive clay soil guide.
Signs you need drainage work
- Water pools within six feet of the foundation after rain
- Soil pulls away from the slab edge in summer
- Musty crawl space or white efflorescence on stem walls
- Cracks that widen only on the downhill side of the lot
- Gutters that dump at the corner with no extension
- Mulch or soil piled against brick, trapping moisture
Related structural signs: foundation problem checklist. If floors already slope, book an elevation survey rather than guessing that a French drain will level the house.
Solutions we install
Surface grading re-pitches soil away from the house. Swales intercept uphill runoff on sloped lots in Boerne and New Braunfels. French drains collect subsurface water along the footing and route it to daylight or a legal discharge. Downspout extensions keep roof volume from hammering one corner. Catch basins help low spots that grade cannot reach.
Order of operations: fix roof water first (gutters and extensions), then grade, then subsurface drains if the clay along the footing stays wet. Many jobs need both grade and a drain. A drain under a yard that still slopes toward the house is a buried gutter fighting gravity.
Foundation drainage repair cost in San Antonio
Linear feet of drain, soil export, and hardscape access set the price. Combined pier packages are quoted after survey.
| Scope | Typical range |
|---|---|
| Downspout extensions & surface grading | $1,500 – $3,500 |
| Swale or berm along one slab side | $2,500 – $5,000 |
| French drain (single side, 50–80 ft) | $3,500 – $8,000 |
| Full perimeter drainage + grading | $8,000 – $15,000 |
| Combined drainage + piering package | Quoted after survey |
Ranges reflect San Antonio market conditions. Final price depends on inspection findings. We quote in writing before work begins.
Drainage is cheaper than a second pier lift. It is not a substitute for piers when corners are already down. Full repair ranges: San Antonio cost guide.
Soaker hoses: maintenance, not a repair
Consistent perimeter moisture during drought slows clay shrinkage that pulls slabs down. Place soaker hoses 12–18 inches from the foundation, not against the brick. Run them on a timer in dry months. Skip them when the yard is already saturated. They cannot reverse settlement that already happened. Forum arguments that watering is a scam miss the point: watering is moisture management. It is not a $12,000 pier package in hose form.
We include a moisture plan in inspection reports when it applies. If your lot is a bowl that holds water, more watering is the wrong move. Grade and drains first.
When drainage avoids piering vs when it only protects piers
If elevation is still acceptable, cracks are seasonal, and doors mostly work, drainage plus watering can be the whole plan. That is the one-in-five inspection outcome we like. If a Converse or Schertz corner is already down and stays soft after rain, we fix drainage in the same scope as piering. Piering without drainage is like fixing a roof leak without replacing the flashing.
Northeast Bexar ranchland lots are flat. Water has nowhere to go unless you create a path. Hill Country lots in Boerne do the opposite: concentrated runoff hits one downhill corner. Same clay physics, different geometry.
French drain vs regrade vs downspouts
Downspouts are the cheapest win. A roof dumps thousands of gallons on a few corners. Extensions that carry water 4–6 feet (or more) off the slab are not optional trim. Grading is next when the soil itself slopes toward the house. French drains help when subsurface flow or a high water table keeps clay fat along the footing even after the surface looks dry.
We inspect runoff during or right after rain when possible. Stain lines and silt fans tell the story if we miss the storm. Crawl-space homes with wet dirt need this work before lumber replacement on pier and beam repair.
What to expect
Most drainage projects take one to three days. Trenches along the slab are backfilled and sodded or rocked. We document finished grade so you know water should exit the property, not sit against brick. You can stay in the home. Written warranty covers the installed drain and grade work, not a promise that clay will never move again. San Antonio clay always moves a little. The goal is even moisture, not a museum slab.
Insurance typically excludes gradual soil and water seepage. Sudden covered events are a policy question. Selling? Buyers notice ponding. A documented drainage fix plus a stable survey is easier than a yard that still lakes at the patio.
A simple soaker-hose calendar for Bexar clay
July through September, when lawns go dormant and soil pulls a finger-gap from the slab, run soakers early morning a few days a week. Keep them 12–18 inches out. Do not soak against veneer. After a two-inch rain, shut them off. In January they often idle. The goal is even moisture, not a swamp. If you have a watering system already, we will tell you whether the heads actually hit the perimeter or only the middle of the yard, which does the foundation no good.
DIY downspout extensions are fair game: rigid pipe, splash blocks that actually reach past the clay backfill, not a two-foot flimsy tube that kinks. Buried drains that dump into the neighbor’s yard or a city inlet without a legal path are not a DIY weekend. That is how you buy a dispute. We design discharge to daylight on your lot or to an approved point.
What a combined drainage and pier package looks like
Survey first. If the corner is down and wet, the written estimate has two line items: steel or helical piers, plus grade or French drain on that side. You can stage them: drain this month, piers next, if movement is slow and budget is tight. We will not pretend staging is free of risk. Active drop wants both. Northeast Bexar flats often need more linear feet of drain than a Helotes hillside that only needs a swale and extensions.
Dry wells and pop-up emitters work when daylight is not available. They still need soil that can accept water. Dumping a roof into a dry well next to the footing is relocating the problem two feet. We will not install that. Crawl-space vapor barriers without exterior water control are the same mistake indoors. Fix the source, then the symptom.
If a landscaper already built a patio that traps water against the slab, we will say the patio has to change. Pretty hardscape that lakes at the brick is a foundation problem with extra steps. We would rather redesign a small patio slope than install a French drain that fights a sunken paver bed forever. That conversation happens at inspection, before we trench.
Related guides
Book a free drainage and foundation inspection: (830) 244-0222. Serving Bexar, Comal, Kendall, and Guadalupe counties.
San Antonio Slab Repair · 454 Soledad Street, 3rd Floor, San Antonio, TX 78205 · (830) 244-0222
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Drainage & Soil Correction
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