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How much does crawl space encapsulation cost in Seattle?
In the Seattle metro in 2026, crawl space encapsulation typically runs $10,650 to $13,000. A full premium scope — dehumidifier, closed-cell foam at the rim joists, heavier liner, wall coverage — reaches $15,675 to $21,500. 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.
Those numbers assume the crawl space does not have a water problem. If it does, drainage is a separate line item at $4,025 to $7,175, and it comes first. That single distinction explains most of the difference between a quote a homeowner expected and the one they received.
Encapsulation cost by crawl space size
The range above prices a crawl space of 1,200 to 1,500 square feet. For other sizes, the cost calculator scales the whole range by the size of the floor, and these are the figures it returns:
| Crawl space floor area | Modeled 2026 range | Against the published range |
|---|---|---|
| Under 500 sq ft | $6,200 to $7,500 | About 42% below it |
| 500 to 1,000 sq ft | $8,200 to $10,000 | About 23% below it |
| 1,000 to 1,500 sq ft | $10,650 to $13,000 | The published range |
| Over 1,500 sq ft | $13,100 to $16,000 | About 23% above it |
Three things to read alongside the table. The figures are modeled estimates like every range on this site, scaled and rounded to the nearest $100, before sales tax, and the methodology page shows how they are built. They keep every other condition at the reference job: a damp crawl space, easy access, no failed insulation to remove and no drainage or mold work, each of which the calculator prices separately. And the model has a single bracket above 1,500 square feet, so it returns the same figure for a 2,000 square foot crawl space as for a 3,000 square foot one; a much larger space runs higher still, and only a written quote will say by how much.
Why this is higher than the national average you have seen
If you have already searched this, you have probably seen a national figure around $5,500, or a Seattle average of $6,111 on Angi. Our range starts at $10,650. That gap is real — about 74% above the Seattle average and roughly double the national one — and it deserves a straight answer rather than a footnote.
The difference is scope, not market. The large aggregators publish encapsulation across a very wide band. HomeGuide puts it at roughly $3 to $10 per square foot nationally, and Angi’s Seattle page gives $5,555 to $16,665 for the whole job (both checked November 2026). A single blended “average” sits near the bottom of those spreads and describes the simplest jobs in them, not a full one.
The range on this page prices a full scope, because that is what the table above actually contains: a heavy liner across the floor and up the foundation walls, mechanically fastened, with the vents sealed, the access sealed, and every seam, pier and penetration sealed. On a mid-sized 1,350 square foot crawl space, $10,650 to $13,000 works out to roughly $7.89 to $9.63 per square foot — in the upper part of that per-square-foot band. Across the full reference range of 1,200 to 1,500 square feet it spans $7.10 to $10.83, the top of which runs past the ceiling of that band. Compared like with like, the number sits where a full scope would.
Two further things worth knowing when you weigh a national figure against a local one. National averages blend dry climates with wet ones, and a crawl space that takes on water every winter is not the job a blended average describes. And Angi says its city pages are national figures adjusted by the Bureau of Economic Analysis price parities — the same index this site uses to move its own model to Seattle. Neither is an independent measurement of Seattle prices, which is worth knowing before you treat either as ground truth.
We would rather say all of that than quietly publish a lower number. The ranges here are modeled estimates, not collected quotes, and the methodology page shows exactly how they are built and what they exclude; the cost index publishes the same figures as data with the basis on every row. If a bid you are holding comes in near the national average, that is not automatically a bargain — it is a prompt to check which end of the band it is actually quoting.
What you get at each price point
There is no industry definition of "encapsulation", so the word covers a wide range of work. This is roughly what each tier of this site’s model prices:
| Range | Typically includes | Usually excludes |
|---|---|---|
| $10,650–$13,000 Standard | Reinforced liner on the ground and up the stem walls, seams sealed, liner attached to the walls, vents and access door sealed, old debris and failed insulation removed | Dehumidifier, drainage, rim joist foam, radon vent and exhaust fan, mold remediation, structural repair |
| $15,675–$21,500 Premium / full | Everything above plus a dedicated crawl space dehumidifier with a condensate line, closed-cell spray foam at the rim joists, a heavier cross-laminated liner, and sometimes a sump | Perimeter drainage on a wet crawl space, significant framing repair |
A bid noticeably below the standard range is usually a liner laid loose on the ground without wall coverage or sealed seams. That is a vapor barrier, and it is a legitimate product — it is just priced at $3,400 to $4,675 and should be described as one. What a vapor barrier costs on its own sets out that scope and what Washington’s code actually asks of it. If a quote is unusually cheap, ask which of the standard-tier items above are missing.
What actually moves the number
Ranked roughly by how much they change a bid:
- Whether water has to be dealt with first. The single biggest swing. A crawl space that takes on water during the wet season needs drainage before a liner, adding $4,025 to $7,175. Encapsulating over an unaddressed water source traps the water under the liner where nobody sees it.
- Square footage. Liner, labor, and dehumidifier sizing all scale with floor area. This is the most predictable driver and the one contractors quote most consistently.
- Existing mold. If remediation is needed first, that is typically $1,600 to $4,025 depending on affected area.
- Dehumidifier or not. A dedicated unit with a condensate drain is the usual difference between the standard and premium tiers.
Sales tax, crawl space height and access, debris, permits and rebates are set out with the Washington and City of Seattle rules behind them in what moves the price in Seattle, below.
One Washington-specific thing worth knowing
Sealing a crawl space closed is not simply a product choice in Washington. The state’s residential code lets the foundation vents go only where two conditions are both met: the ground is covered by 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, with a radon system built to the code’s radon appendix; and mechanical exhaust runs continuously at 1 cubic foot per minute for every 50 square feet of crawl space floor. The alternatives in the model code that Washington’s is built on, including dehumidification and conditioned supply air, are struck out of Washington’s version.
The radon part is not limited to high-radon areas. Washington applies its radon appendix to every building that uses the unvented crawl space method, in any county, and in the seven counties the code lists as high radon potential it does not permit unvented crawl spaces at all. King and Snohomish are not among those seven.
These are rules for new work. For an existing house, the code’s general rule is that alterations and repairs meet the requirements for new construction without the rest of the house having to be brought up to code; how a building department applies that to a crawl space being sealed is a question for its permit desk. It is still the reason a competent contractor will treat “close the vents and add a dehumidifier” as a system with requirements rather than an upsell. If a bid seals the vents and names no radon vent and no exhaust fan, ask how it meets the code. The published range above leaves them out: a radon vent system or continuous exhaust ventilation, where the permit for a sealed crawl space calls for one. Closed vs vented crawl spaces covers this in full, with the code text.
Reading an encapsulation bid
A quote you can actually compare answers all of these in writing:
- Liner thickness in mils, and whether it is reinforced or cross-laminated
- Whether the liner runs up the stem walls, how far, and how it is attached and sealed
- How seams are treated — taped, or overlapped and sealed, and by how much
- Whether vents, the access door, and utility penetrations are sealed
- Whether a radon vent and a continuously running exhaust fan are included, and the fan’s rating
- Which humidity-control method is included, if any, and its sizing
- Whether any drainage, sump, or mold work is in the price or excluded
- What happens to existing insulation and debris, and disposal of it
- Whether the total is before or after Washington sales tax
- The warranty: what it covers, for how long, and whether it transfers on sale
- The contractor’s Washington L&I registration number
You can check a Washington registration through L&I's Verify tool before any work of this scope begins; how to read the record explains what it shows.
Is it worth the money?
That is a genuinely separate question from what it costs, and the answer depends on what problem you are actually solving. If you are weighing the spend rather than comparing bids, is encapsulation worth it in Washington works through the payback math, and vapor barrier vs encapsulation covers the cheaper option honestly. If you want to know how long the system lasts before you commit, that is here.
The figures on this page are modeled Seattle-metro ranges before sales tax, not a quote. A free in-home inspection is how you get a firm number for your specific 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 bags of old insulation 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
In Washington, sealing a crawl space brings three code requirements with it: 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. A bid that closes the vents should name the radon vent and the exhaust fan, and two encapsulation bids that differ on those are not pricing the same work. Leaving the vents open is the code’s default, and it still 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.
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. 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. New wiring is the plainest permit item in an encapsulation: an electrical permit is needed whenever wiring is installed, altered or extended, which covers a new circuit or receptacle for an exhaust fan or a dehumidifier. 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
Encapsulation itself earns no utility rebate here: the liner, the sealed vents and the fan or dehumidifier are not insulation measures. The floor insulation in a project 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 unvented crawl space requirements come from WAC 51-51-0408 and Seattle's copy of the same section, the radon appendix's reach from WAC 51-51-0332 and 51-51-60101, how the code treats an existing house from WAC 51-51-0102, and the rebate scope from the PSE and Snohomish County PUD pages. The price-factor section draws on Washington's sales tax law, 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. The aggregator figures in the national-average section are third-party summaries, named where they appear.
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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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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 51-51-60101 — Appendix F, Radon control methods (AF101 and Table AF101(1)) (WSR 07-01-090, effective July 1, 2007) Checked
The high radon potential counties and what follows from being one. Table AF101(1) lists seven Washington counties: Clark, Ferry, Okanogan, Pend Oreille, Skamania, Spokane and Stevens. King and Snohomish are not in the table. AF101.1: unvented crawl spaces are not permitted in any high radon potential county, and in other areas the appendix applies to any structure built with an unvented crawl space under R408.3.
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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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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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Washington State Department of Labor & Industries, Verify a Contractor, Tradesperson or Business Checked
The official Washington register: registration status, bond, workers compensation account standing, and lawsuits filed against the bond.
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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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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 Encapsulation 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.