Demilec Crawl Space Encapsulation Nationwide

Demilec Crawl Space Encapsulation: The San Antonio Owner’s Guide

If your Demilec crawl space encapsulation liner has torn, pulled away from a pier, or started sagging, you’re looking at a repair that typically runs $1,800 to $4,200 installed in San Antonio, depending on square footage and how much of the existing system is salvageable. We stock Demilec-compatible encapsulation materials on our trucks and can usually start the same week you call. Most homeowners discover the failure the same way: a musty smell that won’t quit, higher summer humidity inside, or a floor that feels damp underfoot even when the AC is running hard.

Call (254) 279-0971

Chase Whitaker and our crew have pulled failed liner out from under houses across San Antonio, from Terrell Hills to Stone Oak, and the pattern is consistent. The liner itself usually isn’t the weak point. It’s the seams, the pier wraps, or the attachment points where Texas humidity and clay soil movement put steady stress on the system.

Which Demilec Models This Applies To

Demilec makes spray foam insulation systems, and when we talk about “Demilec crawl space encapsulation” in San Antonio, we’re almost always talking about a closed-cell spray foam application paired with a vapor barrier liner. The foam does the sealing; the liner does the heavy lifting on moisture control. The specific Demilec product matters less than how it was installed and what’s failing now.

Here’s the compatibility gotcha most homeowners don’t know: Demilec closed-cell foam (like Heatlok HFO or Sealection 500) bonds to the liner differently than open-cell foam does. If a previous contractor used an open-cell product where closed-cell was specified, the liner will eventually delaminate, usually within 2 to 4 San Antonio summers. You can check this yourself: look for a printed label on any exposed foam or ask us to pull a sample. A closed-cell Demilec application feels hard and dense, like a foam cooler. Open-cell feels spongy.

For the liner itself, we match to the original spec. Most San Antonio homes built after 2010 used a 12-mil or 20-mil reinforced polyethylene liner. If yours is 6-mil or thinner, that’s your failure point, and it was undersized from day one. We stock 20-mil reinforced liner as our default replacement because it holds up to the clay-heavy soil we have here.

OEM vs Aftermarket: What We Actually Recommend

Demilec doesn’t manufacture vapor barrier liner as a consumer product line, so there’s no “genuine Demilec liner” to match. What matters is the foam specification and the liner grade. We use industry-standard reinforced polyethylene from manufacturers we’ve verified, paired with Demilec foam where the original foam is still sound. If a homeowner insists on a specific liner brand, we’ll install it, but we’ll tell you straight: the 20-mil reinforced product we stock outperforms most brand-name alternatives in San Antonio’s humidity profile. And it costs less.

Signs Your Demilec Crawl Space Encapsulation Is Failing

• Musty smell that moves upstairs. When the liner tears or a seam opens, soil moisture gets into the crawl space air, and that air migrates up through floor penetrations. It smells like wet cardboard, and it gets worse after rain.
• Floors feel damp or cold in specific rooms. Moisture wicking up through an unsealed section of crawl space will make laminate and hardwood feel clammy, especially in the morning. It’s not your slab; it’s the vapor drive.
• Visible condensation on ductwork or floor joists. If you see water beading on metal ducts under the house, the encapsulation has lost its seal. A functioning system keeps that air dry enough that condensation can’t form.
• Pillowing or sagging liner between piers. This means water is pooling on top of the liner from a plumbing leak or groundwater intrusion. A properly installed liner should sit taut and shed water, not collect it.
• Foam pulling away from the rim joist or piers. Closed-cell foam that’s delaminating means moisture got between the foam and the substrate. In San Antonio’s freeze-thaw-wet-dry cycle, this happens fast once it starts.

Replacement Cost & What’s Included

For a typical San Antonio crawl space between 800 and 1,500 square feet, expect to pay $1,800 to $4,200 for a full Demilec-compatible encapsulation repair. Partial seam repairs and small liner patches run $400 to $900 when the rest of the system is sound. Here’s the honest breakdown:

• 20-mil reinforced liner: $0.35 to $0.60 per square foot, material only
• Labor (removal, prep, install, sealing): $1,000 to $2,200 depending on access and obstruction count
• Pier wraps, seam tape, and termination strips: $150 to $400
• Closed-cell Demilec foam repair at rim joist: $3 to $6 per board foot where re-foaming is needed

Every quote from Laurel Attic Insulation San Antonio is written before work starts. No door-step price changes, no “while we’re in there” surprises. Our 365-Day Done Right Promise covers the workmanship in writing, and if the repair fails, the second visit is free. That’s not a promotional line; it’s on the invoice.

DIY or Call Us?

A homeowner can safely do one thing: inspect. Get under the house with a good flashlight, look for torn liner, standing water, and foam that’s pulling away. Take photos. That’s where the safe DIY work ends.

Installing or patching crawl space liner means working in confined, low-ventilation spaces, cutting material around plumbing and electrical penetrations, and handling foam that off-gasses during application. More importantly, getting the seal right is the whole job. A patch that’s 95% sealed is a patch that failed. Most DIY liner repairs we see in San Antonio last one season before the moisture comes back.

If you found a tear and you want it fixed once, call us at (254) 279-0971. We’ll give you a written price before anything starts.

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