Demilec Vapor Barrier Installation Nationwide

Demilec Vapor Barrier Installation: The New Braunfels Owner’s Guide

Demilec vapor barrier installation in New Braunfels typically runs between $1,800 and $3,400 for a complete crawl space or slab-edge application, depending on square footage and whether the existing barrier needs full removal. We stock Demilec-compatible 10-mil and 15-mil reinforced polyethylene barriers on our trucks, and most residential jobs in the New Braunfels area can be started same-day once we’ve walked the space and confirmed your specs. Homeowners usually figure out something’s wrong when they catch that sharp, musty crawl-space smell drifting up through floor registers, or when their hardwood starts cupping in summer despite the AC running flat out.

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Which Demilec Models This Applies To

Demilec doesn’t sell vapor barrier as a standalone branded SKU the way they sell spray foam. What we’re talking about here is the polyethylene ground cover and perimeter sealing system installed beneath or adjacent to Demilec spray foam jobs, typically in crawl space encapsulations or slab-on-grade perimeter work. If your home was insulated with Demilec Heatlok Soya, Demilec Sealection 500, or an earlier Demilec closed-cell application, the vapor barrier spec should match: 6-mil minimum per ASTM E1745 Class C, though we won’t install below 10-mil in New Braunfels clay soils because the ground movement here tears thinner sheeting inside three years.

To identify what you’ve got now, check the crawl space for a white or clear poly sheet taped at seams with either red Tyco tape or foil-faced butyl. Demilec-certified contractors in the 2016-2020 window often used 6-mil non-reinforced poly with spray-foam perimeter beads; that combination fails first at the seam tape when seasonal humidity spikes. We carry reinforced 10-mil and 15-mil barriers with woven polyethylene scrim, plus Demilec-compatible two-component spray foam for re-bonding perimeter edges where the original foam has pulled away from the sill plate. We are an independent service provider, not affiliated with Demilec.

Signs Your Demilec Vapor Barrier Installation Is Failing

• Musty odor rising through floors even with the HVAC running. This means your vapor barrier has lost its airtight seal at the perimeter or developed tears, letting soil gas and moisture migrate upward. In New Braunfels, the combination of clay-heavy soil and seasonal Guadalupe River basin humidity makes this worse than in drier Hill Country locations.
• Hardwood cupping or laminate swelling, especially in summer. Wood flooring is a hygrometer you can walk on. When relative humidity below the floor deck climbs past 70 percent because the poly barrier is compromised, the bottom of the boards absorbs moisture faster than the top can release it.
• Condensation on ductwork or joists in the crawl space. A properly sealed vapor barrier keeps the crawl space air dry enough that ducts don’t sweat. If you’re seeing droplets on metal, the barrier’s either torn, untaped at seams, or never extended fully to the foundation walls.
• White or chalky efflorescence on block walls. That’s mineral salt left behind when moisture wicks through concrete and evaporates. It means water vapor is moving freely through your crawl space instead of being blocked at the ground plane.
• Pest activity increasing under the house. Termites and rodents prefer damp environments. A failed barrier raises humidity and creates the conditions that draw them in, especially in older New Braunfels neighborhoods near the River Road corridor where slab settling has already stressed the building envelope.

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After

Replacement Cost & What’s Included

Most full vapor barrier replacements in New Braunfels run $1,800 to $3,400 installed. The low end covers a clean, rectangular crawl space under 1,200 square feet with straightforward access. The high end reflects larger footprints, existing barrier removal and disposal, mold remediation pretreatment, or the need to cut and reseal around HVAC platforms and plumbing stacks.

Here’s how that breaks down on a typical job:

• Reinforced 10-mil or 15-mil poly barrier material: $0.85-$1.40 per square foot
• Seam tape, mastic, and perimeter spray-foam bonding: $200-$450
• Labor for removal, prep, and installation: $800-$1,600
• Disposal of old barrier and debris: $150-$300

We don’t quote over the phone for vapor barrier work because access height, pier spacing, and what we find under the old poly change the labor hours significantly. We will walk the space, photograph what we see, and deliver a written price before any work starts. Haven Standard Clause 1: flat price, written scope, written warranty before anyone lifts a tool. The 365-Day Done Right Promise applies to all vapor barrier installations.

DIY or Call Us?

There’s nothing electrically dangerous about rolling out polyethylene sheeting, which is why hardware stores sell 6-mil rolls to anybody. The problems start with what comes after. Seaming the poly so it stays sealed through New Braunfels summer humidity requires proper tape and technique; most DIY jobs we see behind have gaps at piers and perimeter edges that let moisture straight through. Cutting around plumbing and HVAC without tearing the sheet takes experience, and crawling a tight space with a spray-foam gun near your face is a quick way to learn why professionals wear respirators.

What you can safely check yourself: pull back a corner of the existing barrier and look for standing water, mold, or torn sheeting. Note the thickness printed on the poly edge if you can find it. Then call us at (830) 243-6352. We’ll bring a moisture meter and a written scope, and you’ll get the documented photo record and before-and-after readings if we’re also sealing the envelope.

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