Demilec Crawl Space Encapsulation Nationwide

Demilec Crawl Space Encapsulation: The Leander Owner’s Guide

We stock and install Demilec-compatible crawl space encapsulation systems in Leander, with most complete installations running $3,800-$7,200 depending on crawl square footage and existing moisture damage. Same-day assessments are available, and we carry Demilec vapor barrier material and seam tape on our trucks. Most Leander homeowners discover their encapsulation has failed when they notice musty odors returning after a rain, find condensation on HVAC ducts in the crawl, or spot new mold spots on floor joists in the Crystal Falls and Cedar Park West areas where clay soils hold water against foundations.

Call (737) 252-7159

Which Demilec Models This Applies To

Demilec’s crawl space line centers on their closed-cell spray foam (Heatlok HFO Pro and Heatlok XT) paired with reinforced polyethylene vapor barriers in 10-mil, 12-mil, and 20-mil thicknesses. The critical identification point is the barrier’s mil rating stamped on the white edge tape, not the foam itself, since the foam rarely fails structurally. What degrades first is the vapor barrier’s seam tape, the mechanical fasteners at the sill plate, or the dehumidifier drain line that Demilec specs as part of a complete system.

We match OEM Demilec barrier material or source equivalent reinforced polyethylene from Johns Manville and Owens Corning with comparable perm ratings (0.06-0.15 perms for true Class I vapor retarders). The aftermarket decision usually comes down to availability: Demilec’s 20-mil woven reinforced barrier has a 45-60 day lead time from regional distributors in Austin, where we can source equivalent 20-mil material next-day. For Leander’s alkaline clay soils, we spec stainless-stall sill plate fasteners regardless of brand, since standard galvanized staples corrode within 3-4 years here.

Signs Your Demilec Crawl Space Encapsulation Is Failing

• Musty odor returning after rain. The vapor barrier seam tape has delaminated at the overlap joints, letting soil moisture vapor migrate upward. In Leander, this accelerates in spring when the clay swells and releases stored moisture against the foundation walls.
• Condensation on HVAC ducts or plenum. The dehumidifier has failed or the drain line is clogged, pushing relative humidity above 60%. Demilec systems are designed to hold 50-55% RH; above that, the dew point hits ductwork first.
• White or gray mold on floor joists. Air sealing at the rim joist has compromised, typically where the Heatlok foam meets the sill plate. This is the most expensive failure to remediate because it requires removing barrier sections to access the seal.
• Vapor barrier pulling away from walls or puddling on the ground. Mechanical fasteners have backed out or the barrier was inadequately secured at installation. We see this in Leander’s newer subdivisions where builders used 6-mil minimum code barrier without proper fastening schedules.
• Increased energy bills with no HVAC change. The thermal boundary is leaking at the crawl-to-house interface, usually at plumbing penetrations or the subfloor access hatch. Blower-door testing catches this; most homeowners notice the bill first.

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After

Replacement Cost & What’s Included

In Leander, a partial encapsulation repair (barrier replacement, seam re-taping, fastener upgrade) typically runs $1,900-$3,400. Complete system replacement with new dehumidifier, barrier, and rim-joist air sealing runs $4,800-$7,200 for crawl spaces under 1,500 square feet. The range driver is access: Leander’s older homes in the downtown corridor have 18-inch crawl heights that double labor time versus 30-inch new construction.

Every job includes removal and disposal of failed material, installation of new barrier with double-taped seams, stainless-stall fasteners at 12-inch centers, and a written scope with flat price before work starts. We document with photos throughout and provide blower-door readings when the crawl communicates with conditioned space. Our 365-Day Done Right Promise covers all encapsulation work. Call (737) 252-7159 for a written estimate - they’re free, and we publish the price before anyone lifts a tool.

DIY or Call Us?

An owner can safely check the dehumidifier’s reservoir, verify the drain line isn’t kinked, and look for obvious barrier tears. What goes wrong fast: crawling over compromised vapor barrier without proper respiratory protection (disturbed mold spores), using consumer-grade tape that fails in 90 days, or sealing the space without addressing the dehumidifier capacity. Demilec systems are engineered as assemblies; partial fixes often trap moisture rather than control it.

Wes Okafor’s rule from two decades in the trade: seal the envelope first. Then fill it. Crawl space work is confined-space work with real respiratory hazards. If you’re seeing mold or the barrier is more than 30% compromised, call (737) 252-7159. We carry Demilec-compatible material and can often assess and quote same-day in Leander.

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