Crawl space repair

Crawl space work in this metro is largely a pre-1965 housing problem. New construction here almost never produces one: in 2025, 8 percent of new single-family homes completed in the Census South region had a crawl space, against 88 percent built on slab or other foundation types (US Census Bureau). So the crawl spaces that need attention are in older neighborhoods — the pre-war and mid-century blocks of Oak Cliff, Fort Worth's near south side, older Denton and Arlington — where the framing is 60 to 100 years old and has been living above damp Blackland Prairie clay the whole time.

What is actually under there

A raised floor in North Texas is usually a grid of wood beams carried on masonry, concrete or wood pads sitting directly on soil, with floor joists spanning between beams and a perimeter of brick, block or stone. Nothing about that assembly is sealed. Ground moisture evaporates upward into the framing continuously, and the soil beneath the pads swells and shrinks on its own schedule — the county survey describes these clays as soils that "swell when they are wet and shrink and crack when they dry," with movement and pressure enough to crack walls and foundations (USDA Soil Survey of Dallas County). Houston Black clay opens cracks up to 4 inches wide a foot down in dry weather (USDA Official Series Description), and pads set on that surface do not stay level.

The repair menu, in physical terms

Structural work happens on hands and knees. A crew crawls the space, sounds beams and joists with a probe or awl to find rot and insect damage, records floor elevations above, then jacks the affected bay with temporary posts. Failed sill beams are cut out and replaced in sections; sistered joists are bolted alongside damaged members; pads that have settled are excavated, reset on new footings, and shimmed to bring the beam back to plane. Where the original pads were undersized for the load, larger footings replace them. New wood in contact with masonry or soil should be pressure treated, and metal shims are preferable to a stack of cedar scraps.

Moisture work is the other half. A vapor barrier is polyethylene sheeting laid across the ground, lapped at seams and run up the perimeter walls, which cuts evaporation into the framing. Full encapsulation adds a sealed, mechanically attached liner, sealed vents, and usually a dehumidifier. Where standing water collects, an interior perimeter drain — trench, perforated pipe, gravel, and a sump if there is no gravity outlet — moves it out. In this soil, permeability is the reason water lingers: the Denton County survey lists "very slow permeability" among the main limitations of these clay map units (USDA Soil Survey of Denton County).

Prices

National cost data puts structural crawl space repair at $2,500–$8,000, a vapor barrier at $1,200–$4,000, a crawl space drainage system at $4,000–$12,000, and joist replacement at $350–$1,000 per joist (HomeGuide). Encapsulation runs $3–$10 per square foot, or $3,000–$15,000 for a typical space (HomeGuide), and an interior crawl space drain line is $20–$40 per linear foot (HomeGuide). Texas-specific figures exist for the structural side: sill beam replacement $4,000–$12,000, localized beam or joist repair $1,500–$6,000, and full sub-floor structure rebuild $15,000–$30,000 or more (Texas Foundation Compass). No Texas-specific encapsulation pricing was found in published sources, so treat the square-foot figures above as a national benchmark rather than a DFW quote.

Permits are more likely than owners expect

Crawl space work often falls squarely inside the local definition of foundation repair. Grand Prairie defines it to include "leveling, installation and/or replacement of piers, footings, or any modification/alteration of any part of the flooring system," and requires a stamped engineer's letter and plans with review taking 5 to 10 business days (City of Grand Prairie). Replacing joists or resetting pads is a modification of the flooring system. Ask the contractor who pulls the permit before work starts.

What to ask, and what a weak bid looks like

Ask for photographs of every condition being repaired, from under the house — this is the one service where an owner cannot easily verify the work. Ask which specific members are being replaced versus sistered, how many pads are being reset, what the new footings consist of, and whether shims are metal or wood. Ask what the moisture source is believed to be, and whether the plan addresses surface grading and downspouts outside before sealing anything inside. Ask whether vents are being kept or sealed, and if sealed, how the space is being conditioned.

Warning signs: a lump sum with no member-by-member scope, encapsulation proposed while rotten framing is left in place, a dehumidifier sold before the water source is identified, "leveling" quoted with no elevation readings before or after, and untreated lumber specified for anything touching soil or masonry.