Crawl Space Vapor Barrier Cost in Portland

The short answer

A standalone crawl space vapor barrier in the Portland metro typically runs $3,225 to $4,425 in 2026 for a code-compliant reinforced sheet across the full soil area, run up the stem walls and sealed. A premium 20-mil cross-laminated barrier with full wall coverage and double-sealed seams runs $4,675 to $6,375.

Against the published reference crawl space — 1,200 to 1,500 square feet of floor — that works out to roughly $2.15 to $3.69 per square foot, everything in. Read that as the widest band the published figures allow rather than a tight one: it divides the cheapest job by the largest reference space and the dearest by the smallest, because the methodology page does not claim which end of the area range each end of the price range describes. It is derived from the range and the reference project rather than quoted separately, so the two cannot drift apart.

The single most useful thing to establish first is whether you are being quoted a vapor barrier at all. The word gets used for two jobs that differ by roughly three times in price. If your quote is near $10,100, you are looking at encapsulation, not a barrier.

What Oregon code requires, and what contractors sell

Almost every vapor barrier conversation in this market happens in mils — 6, 10, 12, 20 — and almost every homeowner comes away believing that thickness is a compliance question. It is not.

Vapor retarder thickness in mils. The code specifies a Class I vapor retarder by permeance, not by mil rating, and nothing in the 2026 matrices changes that.

What Oregon's R408.2.1 actually specifies is a Class I vapor retarder — a permeance rating of 0.1 perm or less under the model code's own definition — plus geometry: joints lapped not less than 12 inches, and the edges run not less than 12 inches up the perimeter foundation wall. A sealed, unvented crawl space carries the equivalent requirement under R408.3, where Oregon asks for 12 inches up the stem wall against the model code's 6. Those are the things an inspector can hold a barrier against. The 2026 code tracker records both provisions as retained unchanged in the 2026 edition, which took effect on October 1, 2026.

One place a mil figure genuinely does appear. Oregon's radon-control appendix (AF103.5.1) calls for a minimum 6-mil polyethylene soil-gas retarder where radon-mitigating construction is required — which covers new construction across most of this metro. That is a different requirement doing a different job, and it is a floor rather than a recommendation. It does not turn the R408 ground-cover rule into a thickness rule, and it does not apply to retrofitting an existing crawl space, which is what nearly every quote discussed on this page is for.

This matters commercially in one specific way. A contractor quoting 20-mil is not quoting you more compliance than one quoting 10-mil, because both clear the same bar. They are quoting more durability — resistance to the foot traffic, tool weight and rodent activity that actually ends a barrier's life. That may well be worth paying for. It is simply a different argument from the one usually made, and knowing which argument you are being sold is what lets you judge the price.

The two questions worth asking any bidder, in this order: what does the barrier terminate against at the wall, and how are the seams sealed? A heavy sheet lying loose with untaped joins performs worse than a lighter one properly fastened and taped, and the geometry is the part the code actually cares about.

What each thickness is really for

Note what the middle row says: the useful jump is from unreinforced to reinforced, not from one mil number to a bigger one. Two 12-mil products, one with scrim and one without, are not the same purchase.

It also helps to know how little of the bill the sheet itself is. Across the national cost publishers, materials-only figures for a reinforced barrier land between roughly $0.30 and $0.70 per square foot depending on thickness, against an installed figure of about $2 to $4 per square foot (national figures, checked September 2026). So going from the thinnest sheet to the thickest roughly doubles the material line, while the material line is a fraction of the job. Thickness upgrades move a small number, not a big one.

Replacing a failed barrier vs covering bare soil

Most Portland-metro vapor barrier jobs are replacements rather than first installations, and it is worth knowing which one you are buying because the labour differs even though the price band does not.

Census figures put a large share of this metro's housing stock well before ground cover was routine — the climate and housing dataset carries the pre-1950 share for 18 metro cities — so most older crawl spaces here have had something put down at some point. What is usually found is thin sheet, displaced around pier bases and utility runs, torn along the traffic path, and chewed where rodents have been.

• Replacement adds removal, bagging and disposal of the old sheet, which is dirty work through a small hatch. It often gains time back on preparation, because the soil beneath an old barrier is usually already levelled.
• First installation over bare soil skips the removal but frequently needs grading, debris clearance and sometimes a moisture problem addressed before anything is laid.

Both land inside the published range. What pushes a job past it is not which of the two it is, but clearance: a crawl space you cannot kneel in costs more for identical square footage, because everything happens lying down.

Where this stops being a vapor barrier job

A vapor barrier does one thing: it stops moisture evaporating out of the soil. Three findings commonly turn a barrier quote into something larger, and each has its own price:

The middle row is the one that costs people money in the wrong order. If water is arriving under the house, a barrier laid over it is a lid, not a fix. Working out which of the three rows you are in is most of what a free inspection is for, and vapor barrier versus encapsulation walks through the decision without a contractor in the room.

The comparison that trips people up

Search this and most of what comes back is priced as encapsulation, with the barrier buried inside it as a line item. The gap that creates is easiest to see per square foot: as a component of a larger encapsulation, national publishers put the barrier at roughly $1.35 to $2.00 per square foot, against about $2 to $4 per square foot for the same barrier bought as a job on its own (national figures, checked September 2026). Same sheet, same house, roughly double the rate — because a component price assumes a crew that is already down there.

The practical consequence is a specific mistake: a homeowner reads a component figure, decides their standalone quote is high, and negotiates against a number that was never describing their job. A standalone barrier job carries its own mobilisation, its own removal and disposal, and its own trip through a small hatch, none of which get cheaper for being the only thing happening that day. The checklist below is how you tell which kind of figure you are holding.

What a vapor barrier quote should itemise

Two bids on the same crawl space can differ by a thousand dollars and both be reasonable, because they are not quoting the same scope. These are the lines that explain most gaps:

• Square footage of soil actually covered, and whether that includes under ductwork and behind piers.
• Material, named — thickness and whether it is reinforced. "12-mil" alone does not settle it.
• Wall coverage and termination — how far up the stem wall, and fastened with what.
• Seam method — tape type, single or double, and whether penetrations and piers are individually sealed.
• Removal and disposal of the existing barrier, where there is one.
• What is excluded. On this site's published figures, a barrier quote excludes drainage, insulation work, any mechanical conditioning, and sealing the foundation vents — that last one being the line that quietly converts the job into encapsulation.

The bid checker walks a written estimate through these line by line. Ranges on this page are modelled Portland-metro market figures rather than a quote — how they are produced is published in full, including what they are not. Portland Crawlspace Pros connects homeowners with independent licensed contractors and does not perform crawl space work; a free in-home inspection is what produces a firm number.