Demilec Crawl Space Encapsulation Nationwide

Demilec Crawl Space Encapsulation: The Round Rock Owner’s Guide

Demilec crawl space encapsulation systems in Round Rock typically run $3,800-$6,200 installed for a standard 1,200-1,800 sq ft crawl, and we stock the full membrane and seam-tape inventory for same-day starts on most Demilec-compatible jobs. Most Round Rock homeowners realize something’s wrong when their spring energy bills spike or they catch a musty smell climbing through the laundry room floor - signs that the 10-20 mil vapor barrier has torn at a seam, the tape has delaminated, or groundwater is getting past the sump discharge point.

Call (737) 259-7528

Which Demilec Models This Applies To

Demilec doesn’t sell crawl space encapsulation as a branded kit the way they package spray foam systems. What we call “Demilec encapsulation” in Round Rock usually means a crawl that was originally sealed with Demilec’s Heatlok HFO or 500 open-cell foam on the rim joist, paired with a third-party poly membrane on the floor. The membrane itself is often unbranded 12-mil or 20-mil reinforced polyethylene, and the failure point is almost never the foam - it’s the tape, the membrane, or the drainage detail.

To identify what you’re working with, look for a yellow Demilec lot sticker on the rim joist foam (usually dated 2016-2022 in the Round Rock market), then measure your existing membrane thickness with a tape measure at a seam edge. If you’re at 6-mil builder-grade poly, that’s not Demilec-associated work and needs full replacement, not patching. We also stock Reflectix radiant barrier for hybrid systems where the original installer layered foil over foam. OEM Demilec tape isn’t available retail; we use a commercial-grade butyl tape rated for damp-substrate adhesion that outperforms the original acrylic in Williamson County’s clay-heavy, slow-drying crawl environments.

Signs Your Demilec Crawl Space Encapsulation Is Failing

• Musty odor rising into living spaces. This means your vapor barrier has lost its seal at a seam or penetration, letting soil moisture evaporate into the crawl air. In Round Rock’s black clay soils, seasonal expansion and contraction pull tape away from wall junctions faster than in sandy regions.
• Visible condensation on ductwork or floor joists. When the relative humidity in a sealed crawl climbs above 65%, cold ducts sweat. The encapsulation is no longer doing its one job: separating the crawl environment from the ground.
• New or worsening floor softness above the crawl. Moisture reaching subflooring swells the OSB or plywood. We’ve found this in Fern Bluff and Behrens Ranch homes where the original 6-mil poly was taped directly to porous block walls without a termination bar.
• Sump pump running constantly or new standing water. Either your perimeter drain was never tied in, or the membrane has torn at the sump pit cutout. Demilec foam on rim joists doesn’t fail, but it doesn’t stop groundwater either.
• Increased allergy symptoms or pest activity. A failed seal reverts the crawl to outside air exchange, pulling in pollen, mold spores, and the humidity that draws millipedes and springtails. We’ve seen this spike in Round Rock’s April-June wet periods.

Replacement Cost & What’s Included

Most full encapsulation replacements in Round Rock run $3,800-$6,200 for a 1,200-1,800 sq ft crawl, with smaller partial repairs at $1,400-$2,800. The range depends on three things: membrane grade (we spec 20-mil woven-reinforced for longevity in Central Texas), whether the rim joist Demilec foam needs spot repair or is intact, and drainage - whether we need to add or replace a sump and discharge line.

Every job includes removal of failed material, substrate prep, new membrane with double-taped seams, mechanical termination at walls, and a post-install photo record. Where the original Demilec foam is sound, we seal to it; where it’s degraded, we patch with fresh closed-cell. Under our 365-Day Done Right Promise, you get a written scope and written warranty before anyone starts, plus the documented photo record when we leave. We also publish before-and-after blower-door numbers on jobs where the crawl connects to conditioned space through bypasses.

DIY or Call Us?

There’s no high-tension danger in crawl encapsulation, but there’s a sequencing trap that wastes money. An owner can safely check: membrane thickness at seams, whether tape is lifting, whether the sump discharge line is blocked or frozen. What goes wrong in DIY is surface prep - taping over damp concrete or clay, skipping the termination bar, or using hardware-store duct tape that releases in 90 days. Seal the leaks first. The insulation has nowhere to go until you do. That applies to the crawl too: the membrane seal is what makes the assembly work. If your Demilec foam is involved, you’ll need compatible materials most suppliers don’t stock. Call (737) 259-7528 and we’ll walk through what you’re seeing - free second opinion on any written estimate you already have.

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