Demilec Crawl Space Encapsulation & Vapor Barrier in San Antonio: What to Know First
Demilec spray foam and vapor barrier systems in San Antonio crawl spaces typically need professional encapsulation work when the original installation has pulled away from foundation walls, wicking moisture from our clay-heavy soil. Most Demilec encapsulation jobs we take on are completed in one to two days, and we give you a written price before any work starts. This page covers the Demilec-specific failure patterns we see across San Antonio, what encapsulation actually involves, and what it costs. If you own a home with Demilec products under it and something doesn’t look right, call us at (866) 751-4428 and we’ll talk it through.
How Demilec Products Fail - and How We Fix Them
- Heatlok HFO Pro separation from stem walls. This closed-cell foam line needs the substrate bone-dry to bond. San Antonio’s summer humidity and winter condensation cycles cause the foam to delaminate in sheets, especially on the east-facing foundation walls that get morning sun. We remove the failed sections, prep the masonry, and re-bond using Demilec’s specified primer process – then re-seal the sill plate junction where most air and moisture intrusion starts.
- Sealection 500 sagging in open crawl spaces. This open-cell half-pound foam wasn’t designed for exposed underfloor applications where San Antonio’s high dew points keep surfaces damp for months. We regularly find it waterlogged and sagging away from the subfloor in homes built between 2008 and 2015. The fix is removal of the saturated material, drying the joist bays, and reinstalling a closed-cell product rated for below-grade exposure.
- Vapor barrier seams splitting at the overlap. Many San Antonio Demilec homes have 6-mil polyethylene vapor barrier that was taped at the seams instead of mechanically fastened. The tape adhesive fails within three to five years in our humidity, and the seams open up like a zipper. We overlap at least 12 inches, seal with mastic designed for below-grade use, and pin the barrier to the soil with retention discs so it can’t shift.
- Pier and column encapsulation gaps. Closed-cell Demilec foam applied around crawl space support piers cracks where the concrete expands and contracts with San Antonio’s temperature swings. Those hairline cracks let ground moisture wick up the pier and into the floor system. We cut back the cracked foam, seal the pier top with an elastomeric membrane, and re-encapsulate so the bond can flex without breaking.
- Band joist foam shrinkage. Demilec’s open-cell products can shrink slightly after curing. In San Antonio crawl spaces, that shrinkage is enough to break the air seal at the band joist, which is exactly where the hottest, most humid outside air pushes in during July and August. We re-apply foam to the band joist at full depth and verify the seal with a smoke pencil before we call the job done.
Our Demilec Crawl Space Encapsulation & Vapor Barrier Process
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We inspect the entire crawl space – every pier, band joist, stem wall, and the existing vapor barrier – and document what’s failing with photos you can actually see.
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We give you a written price for the encapsulation scope, whether that’s seam repair, full barrier replacement, or a complete re-foam of the perimeter. No vague verbal ballparks.
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We source the right material. For Demilec re-foam work we use the appropriate closed-cell product rated for below-grade San Antonio conditions. For aftermarket components like vapor barrier and fasteners, we use products that meet or exceed Demilec’s original spec – never cheap generic drop-ins.
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We do the work carefully. Technicians wear full protective gear, seal off access points to keep foam dust and debris out of your living space, and work section by section so nothing gets missed.
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We test before we leave. We check the vapor barrier for continuity, run a moisture meter along the encapsulation seams, and confirm the perimeter seal with a smoke test.
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We back it with our lifetime workmanship guarantee – the Done Right Promise. If it’s not done right, we make it right.
What Demilec Crawl Space Encapsulation & Vapor Barrier Costs in San Antonio
Here’s what we actually quote for Demilec encapsulation work in San Antonio homes:
- Vapor barrier seam repair (20-40 linear feet of split seams): $350-$700
- Full vapor barrier replacement for a 1,200-1,500 sq ft crawl space: $2,400-$4,200
- Partial foam re-application at band joist (one side of the home): $900-$1,800
- Complete Demilec perimeter re-foam and encapsulate (1,200-1,500 sq ft): $5,500-$9,500
- Crawl space cleanout and debris removal before encapsulation: $400-$1,100 depending on access and volume
What moves the price: crawl space height (anything under 3 feet of clearance slows us down), the condition of the existing Demilec foam, whether standing water needs to be removed first, and the number of piers and columns. Every quote we write in San Antonio includes a line-by-line breakdown. Call (866) 751-4428 for a free estimate – and remember, seniors and veterans get 10% off, always.
Why San Antonio Homeowners Call Walt’s Insulation for Demilec Work
We started this business in 2000, and we’re the one down the road, not a franchise with an 800 number and a rotating cast of subcontractors. Walt Brenner grew up on the north side of San Antonio near Brackenridge Park and built this company because he watched too many homeowners get sold materials that couldn’t handle South Texas heat and humidity. We answer the phone live 24/7, every technician who walks into your house is background-checked and in uniform, and every Demilec encapsulation job is covered by the Done Right Promise. If it’s not done right, we make it right – no runaround. We also work with Reflectix for radiant barrier applications where a Demilec foam product isn’t the right fit, so you get the honest recommendation, not a sales pitch for one brand.
FAQs
As an independent Demilec service provider, we work in a way that preserves any remaining material warranty you may have. We use Demilec-specified primers and compatible products for re-bonding, and we document every step so you have a paper trail. If the original installation was done by a certified Demilec applicator and the material itself is defective, we’ll tell you to file a claim – we won’t bill you for work the manufacturer should cover. Call (866) 751-4428 and we’ll walk you through what applies to your specific situation.
You can absolutely fix just one section if that’s what the problem calls for. We do partial repairs all the time – a split vapor barrier seam, a failed band joist, a single pier with cracked foam. We’ll tell you honestly whether a patch is enough or whether you’re chasing a losing battle. Sometimes the partial fix is the right call; sometimes the whole encapsulation is cheaper over three years than patching repeatedly.
Most San Antonio Demilec encapsulation jobs can be scheduled within a week, and if you’ve got standing water or visible mold growth, we’ll make it a priority and often get there same day or next day. Live person answers the phone 24/7, so call (866) 751-4428 and tell us what you’re seeing under the house.
For a vapor barrier that’s less than eight years old with isolated seam failures, repair is usually cheaper – figure $350 to $700 for the typical San Antonio home. Once the barrier is riddled with splits, torn at the piers, or saturated with groundwater wicking up from below, replacement runs $2,400 to $4,200 and is the better money spent. We’ll show you photos of what we found and let you decide with real numbers in hand.
Yes. Bring us any written estimate from another San Antonio contractor and we’ll give you a free second opinion. If we can’t beat the price, we’ll tell you that too. No trip charge inside our service county, and if your repair comes out over $200, there’s $40 off. Call (866) 751-4428.
Written by Walt Brenner, Owner, Walt’s Insulation at Walt’s Insulation, serving San Antonio and nearby areas.