Johns Manville Crawl Space Encapsulation Nationwide

Johns Manville Crawl Space Encapsulation: The Long Beach Owner’s Guide

We stock and install Johns Manville-compatible crawl space encapsulation systems in Long Beach, with most complete installs running $3,800-$7,200 depending on crawl footprint and existing moisture damage. Same-day service is available when we have your liner spec in stock, which covers most JM poly and reinforced vapor-barrier grades. Most Long Beach homeowners discover the problem after a rainy winter week when the musty smell reaches the living floor, or when their energy bill jumps and the crawl is reading 15-20 degrees warmer than it should in July.

Call (424) 415-7031

Which Johns Manville Models This Applies To

Johns Manville manufactures crawl space liners under several product lines, and the part you need depends on what was originally installed. The JM Poly series includes 6-mil, 10-mil, and 12-mil reinforced polyethylene sheets, typically white or clear, with “Johns Manville” and the mil rating printed along one edge. The JM Dura-Last line uses a woven polyethylene scrim between coextruded layers, heavier at 16-20 mil, and carries a different fastening pattern at the seam overlaps. We’ve also encountered JM-rebranded liners sold through distribution that carry only a lot number and mil spec, no series name.

To identify yours: crawl in with a flashlight and read the edge print. If it’s worn off, measure thickness with a caliper at an unstressed corner, and note whether the material tears cleanly (non-reinforced) or shows a crosshatch pattern when cut (reinforced scrim). The compatibility gotcha in Long Beach is that JM’s 10-mil poly from 2015-2019 runs slightly narrower than current stock, 13’6″ versus 14′ on the roll, so a patch job can leave you six inches short on a standard 14-foot crawl. We stock both widths. OEM JM liner is our default, but for budget jobs we use an equivalent reinforced poly from the same mill source, not a hardware-store drop cloth that’ll off-gas and delaminate in two Long Beach summers.

Signs Your Johns Manville Crawl Space Encapsulation Is Failing

• Musty odor rising through floor registers. The vapor barrier has torn at seams or piercings, letting soil moisture evaporate into the crawl air. In Long Beach’s clay-heavy soil zones near Bixby Knolls, that moisture carries a sulfur note that’s hard to mistake.
• Condensation on ductwork or insulation below the floor. Warm humid air is crossing a compromised barrier and hitting cooler surfaces. We see this most in spring when marine layer moisture meets slab-cooled ducts.
• Soft or cupping hardwood floors above the crawl. Chronic humidity above 70% RH is wicking upward through the subfloor. The JM liner isn’t stopping the vapor drive, usually because it’s punctured or the seams have separated.
• Visible tears, pooling water, or rodent damage on the liner surface. Polyethylene degrades with UV exposure, and any light penetration through foundation vents starts embrittlement. A tear at a pier wrap is the failure point; the rest of the sheet may look fine but won’t hold a seal.
• Increased cooling costs with no attic explanation. The crawl becomes a heat sink in summer, pulling conditioned air downward through gaps. We verify this with a blower-door test, isolating the crawl zone to measure leakage.

Replacement Cost & What’s Included

In Long Beach, a full Johns Manville crawl space encapsulation replacement runs $3,800-$7,200 installed. At the low end: a 1,000-square-foot crawl with accessible height, intact piers, and standard 10-mil poly replacement. At the high end: 2,500+ square feet, sagging removal of old liner, mold remediation on joists, and upgrade to 16-mil reinforced with seam taping and mechanical fastening every 12 inches.

Our price includes removal and disposal of existing material, surface prep, new JM-spec liner cut and seamed to your foundation footprint, pier wrapping, perimeter fastening to foundation walls, and a post-install inspection with photos. We don’t start without a written price, and we don’t finish without a Documented Photo Record. The 365-Day Done Right Promise covers seam separation and fastener pullout. If you want the number that proves the fix, we can run a before-and-after crawl-space humidity reading with our digital psychrometer, included.

DIY or Call Us?

There’s no high-tension danger in crawl space liner work, but there’s plenty of ways to waste money. A homeowner can safely check: measure crawl dimensions, photograph the existing liner edge print, and look for standing water that might indicate a drainage problem first. What goes wrong in DIY: seams that aren’t overlapped 12 inches and taped with pressure-sensitive acrylic, piers wrapped with cuts that create funnel points for water, and the common mistake of laying new poly over old saturated material, trapping mold against the subfloor.

We’ve pulled out three homeowner installs in Long Beach this past year where the liner looked decent from the entry but was holding a half-inch water film underneath. Measure first, then insulate - otherwise you’re just trapping the problem. If you want it done once, call (424) 415-7031. We’ll read your existing liner spec over text if you send a photo.

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