Basement waterproofing

This page exists for a small number of houses. Of new single-family homes completed in the Census South region in 2025, 4 percent had a full or partial basement, while 88 percent were built on a slab or other foundation type and 8 percent over a crawl space (US Census Bureau; foundation type data file). Nationally the basement share is 16 percent. That region is far larger than North Texas and covers new construction only, so treat it as a directional proxy rather than a count of DFW basements — but the direction is unambiguous. Six of the 77 companies verified for this directory publish basement waterproofing, consistent with a market where the work is occasional.

A below-grade space in the Metroplex is most likely one of four things: a basement in an older or custom home, a storm cellar, a mechanical or wine cellar under part of the footprint, or a walk-out lower level on a sloping lot. The physics of keeping water out are the same in all four.

Why below-grade construction is hard in this soil

The difficulty is not groundwater in the way it is in the Midwest. It is the clay. Blackland Prairie soils are high in montmorillonite and "swell when they are wet and shrink and crack when they dry," producing "such movement and pressure that walls and foundations will crack" without adequate design (USDA Soil Survey of Dallas County). A basement wall is a retaining wall, and it takes that swell pressure laterally. Local series test plasticity indexes of 28 to 42 in the "very high" shrink-swell class of more than 9 percent volume change (USDA Soil Survey of Tarrant County).

Two properties of this clay define the water problem. First, permeability is very slow — the Denton County survey lists it as a principal limitation of these map units (USDA Soil Survey of Denton County) — so water that reaches the backfill zone does not disperse; it accumulates against the wall as hydrostatic pressure. Second, the soil cracks open in dry weather, with fissures 1/2 to 4 inches wide at a foot of depth in Houston Black clay (USDA Official Series Description). Those cracks deliver storm water straight down the outside face of the wall. A dry summer followed by a heavy September storm is the classic leak scenario here, and it is not a groundwater table event at all.

What the work involves

Exterior work is the durable approach and the disruptive one: excavate to the footing, clean the wall, patch and parge defects, apply a membrane or fluid-applied coating, add a drainage board or dimple mat so water moves down rather than pressing in, lay perforated pipe in washed stone at footing level with a fabric wrap, and backfill in lifts. On a clay site the backfill choice matters as much as the membrane — replacing expansive clay immediately against the wall with a granular fill reduces the swell pressure the wall carries.

Interior work does not stop water entering; it manages water that has entered. That means an interior perimeter drain cut into the slab edge, piped to a sump with a pump and a discharge line, plus a wall vapor membrane. It is chosen when excavation is impossible — an attached garage, a patio, a neighbor's property line.

Before either, do the cheap work: extend downspouts well past the excavation zone, regrade so surface water leaves, and check for irrigation lines soaking the backfill. Sealing the inside of a wall while a downspout empties beside it is a common and pointless sequence.

Cost, and why no range appears here

No Texas-specific published pricing for residential basement waterproofing was found for this guide, so no range is given. That is an honest gap, not an oversight — the sourced local price data in this directory covers piers, drainage, root barriers and inspections because those are what North Texas contractors actually publish. The nearest sourced figure is national and covers one component only: an interior basement perimeter drain runs $40–$85 per linear foot, and a deep exterior perimeter drain at footing level $30–$90 per linear foot (HomeGuide). Use those to sanity-check a line item, not to price a job.

What to ask

Ask the contractor how many below-grade projects they have completed in this area, and to describe one. Ask whether they are proposing exterior or interior work and why. Ask what the water entry path is believed to be, and what evidence supports that. Ask what backfill material goes back against the wall. Ask whether a structural engineer has evaluated the wall itself, since a wall that is cracking horizontally or bowing inward is a structural problem that a coating will hide rather than fix. Ask what the warranty actually covers — "dry basement" guarantees usually exclude wall cracking, slab seepage, and plumbing leaks. A bid proposing an interior system without discussing gutters and grading is starting at the expensive end.