Johns Manville Crawl Space Encapsulation Nationwide

Johns Manville Crawl Space Encapsulation: The Seguin Owner’s Guide

We stock and install Johns Manville-compatible crawl space encapsulation systems in Seguin, with most full encapsulations running between $3,800 and $7,200 depending on crawl space footprint and existing moisture damage. Same-day service is available when we have your liner spec on the truck, which we do for the common JM 10-mil and 12-mil woven reinforced grades. Most Seguin homeowners discover their encapsulation has failed when they catch a musty spike after spring rains in April and May, or when their dehumidifier starts running nonstop and the power bill jumps.

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Which Johns Manville Models This Applies To

Johns Manville does not sell crawl space encapsulation as a branded “system” with model numbers like a furnace. Instead, they manufacture the liner material itself, typically sold through distributors in rolls labeled by mil thickness and reinforcement type. What we see in Seguin crawl spaces is usually JM 10-mil woven polyethylene, 12-mil woven reinforced, or the heavier 16-mil string-reinforced grade used where groundwater pressure is chronic, especially in low-lying lots near the Guadalupe River floodplain.

To identify what you have, look for the printed edge tape on the liner seam overlaps. JM rolls carry a repeating logo and mil rating every 24 inches. If your existing liner is white or gray, unprinted, and tearing at the seams, it is likely a generic big-box grade, not JM. We do not push OEM-only replacement. The JM 12-mil woven holds up well in Seguin’s clay-heavy soil chemistry, but a quality aftermarket equivalent with the same ASTM E1745 Class A rating performs identically and costs less per square foot. The compatibility gotcha: JM’s 16-mil string-reinforced liner is 13 feet wide on the roll, while most aftermarket 16-mil comes 12 feet wide. If your crawl space was done with JM 16-mil in a single pass, a 12-foot replacement leaves you with an extra seam or a shortfall.

Signs Your Johns Manville Crawl Space Encapsulation Is Failing

• Musty odor returning after rain. The liner seam tape has lost adhesion, or the liner itself has punctured on sharp foundation rubble. Seguin’s spring gully-washers push hydrostatic pressure against the foundation walls, and any gap in the seal lets that moisture into the conditioned crawl space air.
• Dehumidifier running constantly or icing up. Your dehumidifier is sized for a sealed space. When the encapsulation leaks, the unit is trying to dry all of East Texas. The compressor works harder, draws more amps, and fails sooner.
• White or gray powder on the liner surface. This is efflorescence, mineral salts wicking through the foundation block and crystallizing on the plastic. It means water is getting behind the liner, and the adhesive bond at the wall terminus is failing.
• Sagging or pooling on the liner floor. The gravel bed underneath was not leveled before install, or the liner has punctured and groundwater is collecting above it. In Seguin’s older homes near downtown, we see this where 1970s pier-and-beam foundations have settled and created low spots.
• Insect or rodent activity increasing. A torn liner is an invitation. Once mice can get under the plastic, they nest in the insulation batts above and the problem moves from moisture to biohazard. We document this with photos every time.

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Replacement Cost & What’s Included

In Seguin, a full Johns Manville-compatible crawl space encapsulation replacement runs $3,800 to $5,400 for a small to medium crawl space (800-1,200 square feet) and $5,400 to $7,200 for larger footprints or spaces with significant prep work. What drives the range: how much old liner and failed tape we are removing, whether the gravel bed needs regrading, and if the foundation walls need crack repair before new liner goes up.

Our price includes removal and haul-away of the old encapsulation, surface prep, new JM or equivalent-grade liner with double-sided seam tape and mechanical fasteners at the wall terminus, and a post-install inspection with photos. We do not quote by the phone. We send a technician to measure, photograph the existing condition, and deliver a written price before any work starts. Haven Standard Clause 1. The 365-Day Done Right Promise covers the installation. The report goes home with you - the numbers do the talking.

DIY or Call Us?

There is nothing electrically dangerous about crawl space encapsulation, and the physical work is not complex. What goes wrong is the prep and the sealing detail. Homeowners who DIY often lay new liner over old, trapping moisture and mold between layers. They use the wrong tape - HVAC foil tape instead of polyethylene-compatible seam tape - and it releases within two summers in Seguin heat. They miss the wall terminus seal, or they do not address the foundation vents, and the encapsulation is compromised from day one.

What you can safely check: look for the JM print on your existing liner edge, measure your crawl space length and width, and note whether your dehumidifier is ducted into the space or just sitting down there. Bring us that information, or text us photos, and we will tell you whether a patch repair or full replacement makes sense. For the actual install, we recommend a crew that has done it before. Call (830) 549-6646 and we will schedule a free look.

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