Last reviewed
The short answer
A standalone crawl space vapor barrier in the Seattle metro typically runs $3,400 to $4,675 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 $4,925 to $6,725. Both are before Washington retail sales tax, which applies to the full contract price: 10.55% in Seattle from October 1 to December 31, 2026.
Against the published reference crawl space — 1,200 to 1,500 square feet of floor — that works out to roughly $2.27 to $3.90 per square foot, everything in but tax. 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 3 times in price. If your quote is near $10,650, you are looking at encapsulation, not a barrier.
What Washington 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. Above 6 mil, it is not.
Vapor barrier thickness beyond 6 mil. Washington’s code names a thickness once: the basic ground cover is 6-mil black polyethylene or an approved equal. Where it asks for more, in the reduced-vent exception and the unvented option, it asks for a Class I vapor retarder and gives no thickness. Nothing in Section R408 calls for 10, 12 or 20 mil.
What Washington’s R408.1 actually specifies for a vented crawl space is a ground cover of 6-mil black polyethylene or an approved equal, with the joints lapped 6 inches and the sheet run to the foundation wall. Where the vents are reduced, the code asks for a Class I vapor retarder over the earth instead, a class rather than a thickness. A sealed, unvented crawl space under R408.3 needs a continuous Class I vapor retarder lapped and sealed 6 inches at the joints and run 6 inches up and sealed to the stem wall, along with a radon system and continuous exhaust. Those are the things an inspector can hold a barrier against. Seattle’s copy of the code reads the same. The Washington crawl space code page tracks the edition in force, which took effect on March 15, 2024, and the proposed 2024 edition, which is not adopted.
One other place a mil figure appears. The code’s radon appendix calls for a continuous polyethylene soil-gas retarder at least 6 mil thick, lapped 12 inches, and Washington applies that appendix to every crawl space built with the unvented method, in any county. It is a different requirement doing a different job, and it is a floor rather than a recommendation. It does not turn the ground-cover rule into a rule for anything thicker. Nor does Section R408 say an existing crawl space must be brought up to it: the code’s general rule is that alterations and repairs meet the requirements for new work without the rest of the house having to, and how that applies to a particular job is for the building department to say.
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
| Thickness | What it is | Where it makes sense |
|---|---|---|
| 6-mil | Plain polyethylene sheet. The thickness Washington’s code names for a vented crawl space’s ground cover; carries no reinforcement. | Rarely the right buy on an occupied house. It is the material that tears, and the labor to lay it is identical to the labor to lay something that lasts. |
| 10–12-mil reinforced | Polyethylene with an embedded scrim so a puncture does not become a tear. | What the typical range above prices. The reinforcement, not the thickness number, is what changes the outcome. |
| 20-mil cross-laminated | Heavier multi-layer sheet, usually with wall coverage and double-taped seams in the same quote. | Poor access where redoing it would be genuinely difficult, a long expected ownership horizon, or a crawl space with regular trade traffic. The $4,925–$6,725 band. |
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 much of the bill the upgrade moves. In this site’s model, going from the typical reinforced barrier to the premium 20-mil scope adds $1,525 to $2,050, and that step buys full wall coverage and double-sealed seams as well as the heavier sheet. The labor of getting through the hatch, removing the old barrier and terminating the new one is the same either way. Thickness upgrades move a small number, not a big one.
Replacing a failed barrier vs covering bare soil
On an older house, a vapor barrier job is often a replacement rather than a first installation, and it is worth knowing which one you are buying because the labor differs even though the price band does not.
In the City of Seattle 38.4% of housing units were built before 1960 — the climate and housing dataset carries the same housing-age shares for all 19 cities this site covers — so an older crawl space may have had something put down at some point. An old barrier tends to fail in predictable places: 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 leveled.
- 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:
| What is found | What the scope becomes | Modeled range |
|---|---|---|
| Damp soil, humid air, no standing water | Vapor barrier — the job this page prices | $3,400–$4,675 |
| Liquid water entering, or pooling in winter | Waterproofing or drainage first — sealing over active water traps it | $4,025–$7,175 |
| Humidity that needs controlling, not just blocking | Encapsulation — sealed vents and access, rim joists, and the ventilation or conditioning that comes with closing the vents | $10,650–$13,000 |
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, or as a per-square-foot figure for laying sheet over open soil. Either way the figure tends to assume a crew that is already down there for a larger job, or a crawl space with nothing to take out first. A standalone barrier job, the kind this page prices at roughly $2.27 to $3.90 per square foot everything in but tax, carries its own mobilization, its own removal and disposal, and its own trip through a small hatch.
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. None of those standalone costs gets 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 itemize
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.
- Sales tax — whether the total includes Washington sales tax or is before it.
- 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 modeled Seattle-metro figures before sales tax rather than a quote — how they are produced is published in full, including what they are not. A free in-home inspection is what produces a firm number for your crawl space.
What moves the price in Seattle
The local conditions that move a quote, each with the Washington or City of Seattle rule or program behind it. Dollar figures are this site’s modeled adjustments before sales tax, the same ones the calculator applies; the documents are listed under Sources. Where a rule is the City of Seattle’s, it says so: other cities set their own.
Sales tax
Every range on this site is before Washington sales tax. A retail sale in Washington includes the labor and services in repairing or improving an existing building (RCW 82.04.050), and the Department of Revenue has the contractor collect the tax on the whole contract price, state it separately from the price, and charge the rate for the place where the work is done. The combined rate in Seattle is 10.55% from October 1 to December 31, 2026, and across the cities this site covers it runs from 9.9% to 10.7%. The department republishes the rates each quarter, and its address lookup decides the rate for a specific house. Before comparing a bid with anything on this page, check whether its total is before or after tax.
Crawl space height and access
Every range on this site assumes a standard exterior or interior hatch with roughly 3 feet of working clearance. The residential code sets only the minimum way in: an access opening through the floor must be at least 18 by 24 inches, and one through a perimeter wall at least 16 by 24 inches (R408.4, a section Washington adopts without amendment). Everything goes in and out through that opening by hand, liner rolls and the old barrier included, so a space that meets the minimum can still be slow to work in. In this site’s model, low clearance adds about $450 in labor time and clearance under 18 inches about $900.
Standing water, and where it can go
The ranges price a crawl space that is damp but without standing water at the time of the quote. Water changes the job, not just the price. Under the residential code, where groundwater can rise to within 6 inches of the finished floor at the perimeter, or surface water does not readily drain from the site, the grade under the house has to be as high as the finished grade outside unless an approved drainage system is provided (R408.6). Where water stands, drainage at $4,025 to $7,175 comes before the liner, and the calculator adds about $725 for water pooling at the time of the quote and $1,800 for standing water, for preparation before the main work starts.
Inside the City of Seattle, where collected water may go is regulated. The city’s Stormwater Code prohibits sending anything but stormwater to a drainage system, then lists uncontaminated water from crawl space pumps, uncontaminated pumped groundwater and approved footing and foundation drains among the discharges it permits (SMC 22.802.020 and 22.802.030); drainage water may go to a sanitary sewer only with the approval of the Director of Seattle Public Utilities. Connecting a drain to the public system takes a side sewer permit from Seattle Public Utilities, which also says footing drains cannot be daylighted to the right of way. These are City of Seattle rules. Other cities have their own, which this site has not read, so outside Seattle the question goes to that city’s drainage or public works desk. Long discharge runs are one of the conditions this site prices into the premium waterproofing band, $7,625 to $10,650.
What the code requires on the ground
Washington’s residential code requires a ground cover of 6-mil black polyethylene or an approved equal, lapped 6 inches at the joints and run to the foundation wall (WAC 51-51-0408, R408.1). The only exception is a crawl space with a concrete slab floor at least 2 inches thick. So a ground cover is the code’s baseline for a vented crawl space, not an upgrade. A heavier liner with sealed seams goes beyond that minimum. Closing the vents as well is a different job with its own requirements: the code lets the foundation vents go only where the earth is covered by a Class I vapor retarder with its joints sealed and its edges sealed 6 inches up the stem wall, a radon system is installed, and exhaust ventilation runs continuously at 1 cubic foot per minute for every 50 square feet of crawl space floor (R408.3). The dehumidifier and supply-air alternatives in the model code are not in Washington’s version.
Debris and what has to come out first
The residential code requires the grade under the house to be cleaned of all vegetation and organic material (R408.5, adopted without amendment), and nothing new goes down over what is already there. Taking out an existing barrier is inside the vapor barrier range. Wet or rodent-damaged insulation that has to come out adds about $2,500 in this site’s model. Droppings and nesting material are wetted and disinfected, not swept or vacuumed dry, and contaminated insulation is bagged, as the CDC sets out, so it takes longer than clearing ordinary debris. Rot found once the space is opened up adds $375 to $1,350 per repair location, and cannot be priced before it is seen.
Permits
No range on this site includes permit fees, which vary by jurisdiction and are usually billed at cost. Inside the City of Seattle the residential code requires a building permit to alter or repair a house, then exempts minor repairs valued at $6,000 or less in any six-month period that do not touch loadbearing support or reduce ventilation, and listed minor work that includes insulating an existing building and like-for-like replacement of deteriorated members (Seattle Residential Code R105.2). The code section does not say how the city treats a ground cover, a sealed crawl space or a sump basin; that is a question for the Seattle Department of Construction and Inspections. A barrier on its own involves no wiring. Where the job adds any, an electrical permit is needed whenever wiring is installed, altered or extended. Plumbing permits in Seattle and unincorporated King County come from Public Health – Seattle & King County, and connecting a drain to the public system takes a side sewer permit from Seattle Public Utilities.
Outside Seattle, the building department of the city or county the house is in sets the rule. Each amends the permit section of the state code itself, and this site has not read their exemptions, so ask that permit desk before relying on a bid that says no permit is needed.
Rebates
A vapor barrier on its own earns no utility rebate here; the rebates are for insulation. Where the floor insulation above the barrier is being replaced anyway, that part can. Which program applies depends on what heats the house. Puget Sound Energy pays $2.50 per square foot, up to $5,000, toward floor insulation where PSE electricity or PSE natural gas is the home’s primary heat: a site-built home built 1989 or before, with 4 inches or less of existing insulation, finished to R-30 or a full joist cavity, with the work done by a PSE-approved contractor who takes the rebate off the invoice. Snohomish County PUD pays $1.00 per square foot in electrically heated homes it serves, for floor insulation going from R-11 or less to R-30, through a PUD registered contractor. Seattle City Light lists no standard insulation rebate; its insulation help runs through HomeWise, the city’s free weatherization program for income-qualified households. The state HEAR program pays toward electric equipment, not insulation. PSE states that its rebates can change or end without notice; the rebate guide has the conditions in full. The federal Energy Efficient Home Improvement Credit covered improvements made through December 31, 2025, so work done in 2026 does not qualify for it.
Sources
The code provisions come from the Washington Administrative Code and the City of Seattle's copy of the residential code, as recorded in this site's Washington code library, not from a contractor's summary of them; the edition in force is set by WAC 51-51-003 and 51-51-008. Housing-age figures are Census ACS data. The price-factor section draws on Washington's sales tax law, R408.1 and R408.4 to R408.6 of the residential code, the City of Seattle's stormwater, side sewer, building, electrical and plumbing permit rules, the CDC's rodent clean-up guidance, the PSE, Snohomish County PUD and Seattle City Light programs, and the IRS page on the expired federal credit.
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Washington State Legislature, WAC 51-51-0408 — Section R408, Under-floor space (Washington State Residential Code, amended by WSR 23-23-104) Checked
What Washington requires under a house: ventilation at 1 square foot per 300 square feet of under-floor area; 6-mil black polyethylene ground cover with joints lapped 6 inches, extending to the foundation wall, which may be omitted where the crawl space has a concrete slab floor at least 2 inches thick; vent coverings with a least dimension of no more than 1/4 inch (corrosion-resistant wire mesh at 1/8 inch), and operational louvers permitted; ventilation reducible to 1/1,500 where a Class I vapor retarder covers the earth, with a radon vent built to Appendix AF required where ventilation is below 1/300 or operable louvers are installed. Vents may be omitted only where both numbered conditions of R408.3 are met: a continuous Class I vapor retarder lapped and sealed 6 inches, extending 6 inches up and sealed to the stem wall, with an Appendix AF radon system; and continuously operated mechanical exhaust at 1 cfm per 50 square feet. R408.8 is not adopted in Washington.
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Seattle Department of Construction and Inspections, 2021 Seattle Residential Code, Chapter 4, Foundations (Section R408, pages 4-47 and 4-48) Checked
Two things. First, that Seattle’s R408.1, R408.2 and R408.3 carry the Washington-amendment marker and read the same as WAC 51-51-0408, apart from “Appendix F” where the state rule says “Appendix AF”; the copy shows the model code’s wording struck through, including its menu of alternatives for an unvented crawl space (dehumidification, conditioned supply air, perimeter-wall insulation), which is how the two numbered conditions of R408.3 are read as applying together. Second, the sections Washington does not amend, R408.4 to R408.6: an access opening not smaller than 18 by 24 inches through the floor or 16 by 24 inches through a perimeter wall; the under-floor grade cleared of vegetation and organic material, and forms and construction materials removed; and the under-floor grade as high as the outside finished grade where groundwater can rise to within 6 inches of the finished floor at the perimeter or surface water does not drain readily, unless an approved drainage system is provided.
Note: The PDF marks additions by underline, which is lost when its text is extracted. “No Seattle-only change to R408” is drawn from the match with the state rule, not from a statement by the city. R408.4 to R408.6 are model code text and are summarised here, not reproduced.
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Seattle Department of Construction and Inspections, 2021 Seattle Residential Code, Appendix F, Radon Control Methods (Section AF103.5, page AF-9) Checked
What the radon appendix asks for under a crawl space. AF103.5 describes a passive sub-membrane depressurization system: a continuous soil-gas retarder of polyethylene at least 6 mil thick, lapped not less than 12 inches and extended to the foundation walls, with a 3- or 4-inch vent pipe run from beneath the sheeting up through the building to at least 12 inches above the roof. The section has an exception for buildings with an approved mechanical crawl space ventilation system or equivalent.
Note: Model code text read in the city’s copy and summarised, not reproduced. The appendix asks for 12-inch laps of the soil-gas retarder where R408.3 asks for 6-inch sealed laps of the vapor retarder; which governs on a sealed crawl space is a question for the building department.
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Washington State Building Code Council (via Washington State Legislature), WAC 51-51-0332 — Section R332, Protection against radon Checked
Where the radon appendix applies. R332.1: to buildings constructed in the high radon potential (Zone 1) counties of Table AF101(1), and also to all buildings constructed using the unvented crawl space method of Section R408.3, in any county.
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Washington State Building Code Council (via Washington State Legislature), WAC 51-51-0102 — Section R102, Applicability (Last amended by WSR 23-23-104, effective March 16, 2024) Checked
How the residential code reaches an existing house. R102.7.1: additions, alterations and repairs conform to the requirements for a new structure without requiring the existing structure to comply with the code, unless otherwise stated, and must not make the existing structure less compliant than it was. Its second exception: additions or alterations that do not require the construction of foundations, crawl spaces, slabs or basements are not required to meet the radon protection requirements of Section R332.1 and Appendix AF. R102.5 names Appendix AF, Radon Control Methods, as included in the adoption.
Note: The section states the general rule. How it applies to a particular repair, and how its radon exception sits with the radon system named inside R408.3, is decided by the building department reviewing the work.
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Washington State Building Code Council (via Washington State Legislature), WAC 51-51-003 — International Residential Code (Last amended by WSR 23-23-104, effective March 16, 2024) Checked
Which edition Washington’s residential code is: the section adopts the 2021 edition of the International Residential Code by reference, with Washington’s additions, deletions and exceptions, and does not adopt chapters 11 and 25 through 43. Energy is regulated by chapter 51-11R WAC instead.
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Washington State Building Code Council (via Washington State Legislature), WAC 51-51-008 — Implementation (Last amended by WSR 23-23-104, effective March 16, 2024) Checked
The date the edition in force took effect: the International Residential Code adopted by chapter 51-51 WAC became effective in all counties and cities of the state on March 15, 2024. This is the section whose date changes when a new edition is adopted.
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United States Census Bureau, American Community Survey 5-Year Estimates — Year Structure Built (B25034) and Median Year Structure Built (B25035) (ACS 2020–2024 5-year estimates, tables ACSDT5Y2024.B25034 and ACSDT5Y2024.B25035) Open dataset Checked
The housing-age columns for the 19 Washington cities in the Seattle-metro climate and housing dataset: total housing units, median year built with its published margin of error, and the shares of units built before 1980, before 1960 and before 1950, each summed from the B25034 decade buckets per Census place GEOID. Pulled through the data.census.gov table endpoint on 2026-11-10; for every place the ten buckets were summed and checked against the table total.
Note: Survey estimates carrying sampling error, not a census of buildings. They cover ALL housing units in a place, apartments included, rather than single-family homes — and the ACS does not ask about foundation type, so nothing here identifies which units have a crawl space.
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Washington State Legislature, RCW 82.04.050 — “Sale at retail,” “retail sale” (Subsection (2)(b)) Checked
That a retail sale in Washington includes the charge for labor and services in constructing, repairing, decorating or improving new or existing buildings for consumers, including installing or attaching tangible personal property. This is why sales tax applies to the price of crawl space work on a home, labor included.
Note: The section was amended twice in 2026 and the Legislature’s page prints more than one version of it. Subsection (2)(b) reads the same in each version on the page.
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Washington Department of Revenue, Construction industry guide: Custom construction Explanatory summary, not the governing text Checked
How the department applies the tax to construction for a landowner: the prime contractor collects retail sales tax on the gross contract price without deducting costs, the invoice must state the tax separately (a quoted price is presumed not to include it), and retail construction services are taxed at the combined rate for the location where the construction takes place.
Note: The department’s guidance for contractors, not the statute. It cites RCW 82.08.050 for the separate-statement rule; this site has not read that section itself.
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Washington Department of Revenue, Local sales and use tax rate table (Quarter 4 2026, effective October 1 through December 31, 2026) Checked
The combined state and local retail sales tax rate for each city this site covers, by Department of Revenue location code: from 9.9% in Everett to 10.7% in Lynnwood and Edmonds, and 10.55% in Seattle. The state rate is 6.5% on every row.
Note: These rates apply from October 1 to December 31, 2026; the department republishes the table every quarter. Several cities have more than one location code, with a lower rate where the Regional Transit Authority tax does not apply or a different rate in a second county. The department’s address lookup (dor.wa.gov/TaxRateLookup) decides the rate for a specific house.
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City of Seattle, Stormwater Code, Seattle Municipal Code Title 22, Subtitle VIII (July 2026 compilation; SMC 22.802.020 and 22.802.030) Checked
Where pumped crawl space water may go inside Seattle: SMC 22.802.020.B prohibits any discharge to a public or private drainage system that is not entirely stormwater, except as SMC 22.802.030 allows; SMC 22.802.030.B lists as permissible, unless the Director of Seattle Public Utilities finds a water quality problem, uncontaminated pumped groundwater, uncontaminated water from crawl space pumps, approved footing drains and other subsurface drains, and foundation drains; and SMC 22.802.030.C lets the Director approve drainage water to a sanitary sewer only case by case.
Note: The city’s own compilation, which it labels unofficial; the Seattle Municipal Code is the official text. These are City of Seattle rules. Every other city in the area has its own stormwater code, which this site has not read.
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Seattle Public Utilities, Side Sewer Permits Checked
That in Seattle a side sewer permit is required to connect a property to the public sewer or a storm drain and to repair, alter or add to a sanitary or drainage side sewer; that the whole side sewer to the public main is owned and maintained by the property owner; that for foundation drains only the solid pipe from the perforated footing drain to the drainage system counts as side sewer; that footing drains cannot be daylighted to the right of way; that piping inside the building is plumbing, permitted by Public Health; and that work in the right of way also needs a Seattle Department of Transportation permit.
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U.S. Centers for Disease Control and Prevention, How to Clean Up After Rodents (Healthy Pets, Healthy People — Rodent Control) Checked
The rule against sweeping or vacuuming dry droppings, urine and nesting material; the 30-minute ventilation step; the bleach dilution (1.5 cups per gallon, or 1 part in 9) and 5-minute dwell time; the instruction to bag contaminated insulation and stay upwind while removing it; and the personal protective equipment specified for heavy infestations, including a HEPA-filtered half-mask respirator.
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Seattle Department of Construction and Inspections, 2021 Seattle Residential Code, Chapter 1, Administration (Sections R105.1 and R105.2) Checked
When a building permit is needed in the City of Seattle. R105.1: a permit is required to construct, alter or repair a building, and all work must meet the code whether or not a permit is required. R105.2 item 1: no permit for minor repairs or alterations valued at $6,000 or less in any six-month period, provided no loadbearing support is removed, reduced, altered or relocated and ventilation is not reduced. R105.2 item 2: no permit, provided the building envelope is not changed, for listed work that includes insulating existing buildings and in-kind or similar replacement or repair of deteriorated members.
Note: City of Seattle only, and it is the building permit only: electrical, plumbing and side sewer permits are separate. The chapter does not say how the department classifies a ground cover, a sealed crawl space or a sump basin.
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Seattle Department of Construction and Inspections, Electrical Permit Checked
That in Seattle an electrical permit is needed whenever wiring is installed, altered, extended or connected to equipment, which covers a new receptacle or circuit for a sump pump or dehumidifier; that a professional applying needs a Washington electrical contractor’s license and a Seattle business license; and that owners may do their own electrical work on a property they own and occupy.
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Public Health — Seattle & King County, Plumbing and gas piping: applications and permits Checked
That plumbing permits in Seattle and unincorporated King County are issued by Public Health — Seattle & King County, not by the city’s building department; that a permit is required to install, relocate or change a plumbing system; and that a property in another King County city gets its plumbing permit from that city.
Note: The page does not say whether adding or replacing a sump pump needs a plumbing permit. The program’s permit-applicability document, which reportedly does, could not be opened, so this site does not state it.
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Puget Sound Energy, Weatherization rebates Checked
The PSE amounts and conditions this site quotes: floor insulation at $2.50 per square foot up to $5,000, in a site-built home built 1989 or before with 0 to 4 inches of existing insulation, finished to R-30 or a full joist cavity, where existing insulation may not be removed to qualify and the thermal boundary may not be moved; floor air sealing at $0.20 per square foot up to $400; duct sealing and insulation up to $1,000 per home, duct sealing only up to $550; that the customer must use PSE electricity or PSE natural gas as the primary source of space heating and live in a single-family home of four units or fewer or a manufactured home; that the work must be done by a PSE Recommended Energy Professional or Trade Ally, who takes the rebate off the invoice; that self-installed work does not qualify; and that the rebate cannot exceed the price of the work.
Note: PSE states that this is a tariffed service that can change or end without notice, and the page gives no program year. The page lists no rebate for a ground cover, vapor barrier, dehumidifier or drainage. It still says a federal tax credit may be available; the IRS says that credit ended for work after December 31, 2025.
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Snohomish County Public Utility District No. 1, Weatherization Rebates Checked
The Snohomish PUD amounts and conditions this site quotes: insulation at $1 per square foot for customers with electrically heated homes, where floor insulation must go from R-11 or less to R-30; duct sealing in a single-family home at $5 per linear foot up to $450; that the customer must own a single-family or manufactured home, or a townhouse or condominium in a building of up to four attached dwellings; and that the work must be done by a PUD registered contractor, who includes the rebate in the bill.
Note: The page states no cap on the insulation rebate and no end date. It lists no rebate for a ground cover, vapor barrier or air sealing.
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Seattle City Light, Home Energy Solutions Checked
That Seattle City Light’s residential page lists no standard rebate for insulation, air sealing or duct sealing: it advises sealing and insulating floors over crawl spaces, and sends insulation help to the income-qualified HomeWise program.
Note: An absence read from one page on one day. City Light’s offers change; check the page before relying on this.
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City of Seattle, Office of Housing, Weatherization (HomeWise) Checked
That HomeWise provides free weatherization, including insulation and duct and air sealing, to income-qualified households: homeowners or renters inside Seattle city limits, and Seattle City Light customers outside the city whose homes are electrically heated; that eligibility depends on income, heat source and whether the home is rented or owned; and that the program selects and manages the contractor.
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Washington State Department of Commerce, State Home Electrification and Appliance Rebates (HEAR) Program Checked
That the state HEAR program’s eligible items are electric equipment (heat pumps, heat pump water heaters, induction cooking, heat pump dryers, and the panel and wiring upgrades they need), and that insulation, air sealing and vapor barriers are not on the list.
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Internal Revenue Service, Energy Efficient Home Improvement Credit Checked
That the credit can be claimed for improvements made through December 31, 2025, so crawl space work done in 2026 does not qualify for it; that it equalled 30% of qualified expenses, with insulation and air sealing materials or systems meeting IECC standards among the qualifying building envelope components; and that it applied to improvements to an existing main home, not to a landlord who does not live in the home.
Note: The IRS summary page, not the statute or the form instructions. It is cited only for the credit’s end date and scope; it says nothing about deductions, rental property or a home sale, which this site does not cover.
Sources last checked between and ; the date beside each one is when it was last opened. Where a figure comes from a document that is revised on a schedule, the edition or version is named above so you can confirm it against the current one yourself.
Estimate Your Vapor Barrier Cost
Modeled 2026 estimates for the Seattle metro, before Washington sales tax (10.55% in Seattle), not collected contractor quotes — how these figures are produced. Adjust for your specific conditions. A free in-person inspection gives you an exact quote.
Crawlspace Cost Calculator
Answer 6 quick questions for a modeled 2026 Seattle-area price range, before sales tax. How these figures are produced.
This range is a modeled estimate for a Seattle-metro project of this size and scope, before Washington sales tax. Sales tax is added to the full contract price at the rate for your address (10.55% in Seattle from October 1 to December 31, 2026). It is not a quote: actual costs vary with the conditions found and the contractor. Get a free in-person inspection to confirm.