Johns Manville Crawl Space Encapsulation Nationwide

Johns Manville Crawl Space Encapsulation: The Los Angeles Owner’s Guide

If you have a Johns Manville crawl space liner or vapor barrier that’s torn, sagging, or pulling away from the foundation walls, we can match it and install the replacement, usually within a few days. In Los Angeles, a full crawl space encapsulation using Johns Manville-compatible materials typically runs $4,200 to $9,800 depending on square footage and how much prep work the space needs. Most homeowners discover the problem the same way: a musty smell drifting up through the floorboards in summer, or a pest control inspector pointing out that the barrier has been shredded by rodents. We’re an independent insulation contractor, not affiliated with Johns Manville, but we stock their products because they hold up better than most in Southern California’s dry heat.

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Which Johns Manville Models This Applies To

Johns Manville doesn’t sell encapsulation as a single “part” the way a furnace has a part number. What you have is a system: their 6-mil or 10-mil polyethylene vapor barrier, typically in the CE series (crawl space encapsulation), paired with JM’s white reflective liner for walls, and their seam tape or mastic for sealing overlaps. The gotcha we see constantly in Los Angeles is this: many contractors install a 6-mil barrier where a 10-mil belongs, and in a city where crawl spaces sit bone-dry for eight months then take on moisture from winter rains, the thinner material fails at the seams first. If your liner is white and fiber-reinforced on one side, you have a JM product. If it’s loose black poly sheeting, you probably don’t. We stock both 6-mil and 10-mil JM vapor barrier on our trucks, plus the matching white wall liner, because a patch job with mismatched material won’t seal correctly. For anything beyond a small tear, we recommend the 10-mil: in our experience across Los Angeles, it lasts 20 to 30 years versus roughly 10 to 15 for 6-mil in active crawl spaces.

Signs Your Johns Manville Crawl Space Encapsulation Is Failing

• Musty or earthy smell in the house, especially in summer. The vapor barrier has torn or separated from the foundation wall, letting ground moisture evaporate up into your floor joists and subfloor. In older Los Angeles neighborhoods like West Adams or Highland Park, this is often compounded by decades-old moisture already trapped in the framing.
• Visible sagging or pooling of the liner. If water is ponding on top of the barrier, water is getting in from outside, either through foundation cracks or poor drainage. The barrier is doing its job; the surrounding waterproofing isn’t. We address drainage before re-lining.
• Rodent droppings, tunnels, or shredded plastic along the edges. Rats and mice love the path along the foundation sill. Once they chew through the vapor barrier, it’s no longer a vapor barrier. In neighborhoods like Silver Lake and Echo Park with dense hillside vegetation, this is one of the most common crawl space calls we get.
• Floor temperature swings between rooms. A failing liner lets cool damp air reach the floor deck unevenly. Rooms over the crawl space feel colder in winter and stickier in summer than rooms over a slab or garage. This is a sign the encapsulation has lost its continuous seal.
• Higher humidity readings indoors, often 60% or above. If you have a hygrometer and you’re seeing humidity creep up in the spring and fall, the barrier has a breach somewhere. In Los Angeles, the transition months are when you’ll notice it, because that’s when the soil moisture gradient is highest.

Replacement Cost & What’s Included

In Los Angeles, the installed price for replacing or upgrading a Johns Manville crawl space encapsulation system breaks down like this:

• Small crawl space (under 800 sq ft), 10-mil liner replacement: $4,200 to $5,800
• Mid-size crawl space (800 to 1,500 sq ft), full encapsulation with white wall liner: $5,500 to $7,500
• Large or complex crawl space (over 1,500 sq ft, multiple access points, pier-and-beam): $7,500 to $9,800
• Drainage correction or sump pump addition: $1,800 to $4,200 depending on scope

What drives the range is access clearance, how much old material has to be removed, whether the rim joists need air sealing, and whether we find standing water that needs a drainage fix before new liner goes down. Every quote includes parts, labor, disposal of the old barrier, and our 90-Day Done Right Promise: if the work isn’t right, we make it right. We quote the whole job upfront before we start, so there’s no surprise line item at the end.

DIY or Call Us?

A homeowner can reasonably inspect a crawl space with a good flashlight and a respirator: look for torn plastic, sagging liner, pooled water, and rodent sign. What you should not do is attempt a full re-encapsulation yourself. Crawl spaces in Los Angeles are tight, often have exposed wiring, and reaching the far corners means working on your stomach or side for hours. More importantly, a liner that isn’t sealed continuously at every pier, post, and wall junction won’t work, period. The vapor barrier only functions when it’s a continuous plane. That’s the part DIY attempts get wrong most often, and it means you’ve spent a weekend breathing dust and gained nothing. If you’re seeing any of the failure signs above, call (213) 782-8141 and we’ll send a technician who’s done this hundreds of times. A live person answers, 24/7, and most jobs are completed in a single visit.

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