Crawl Space Repair Cost in Seattle, WA (2026)

Typical 2026 ranges for Seattle-area crawl space work run from $1,600 (sump pump installation or mold remediation) to $13,000 (crawl space encapsulation), before sales tax. A standalone vapor barrier is $3,400 to $4,675; a drain, sump and ground cover for a wet crawl space is $4,025 to $7,175. Every range below states the project it prices, what it includes, and how it was produced.

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Crawl space encapsulation, repair, and waterproofing across the Seattle metro, starting with a free in-home inspection and a no-obligation quote.

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2026 Pricing

2026 Cost by Service

Every range below is a modeled estimate for the Seattle metro in 2026, before Washington sales tax, priced against a stated reference project rather than a national average — and it is an estimate, not collected quote data. The methodology page sets out the reference project, what each range includes and excludes, and the limitations. For what each job actually involves, the overview of crawl space services walks through every one; this page is about what they cost.

Service Typical Range What Pushes It to the High End
Vapor Barrier Installation Cost detail → $3,400–$4,675 Premium 20-mil cross-laminated barrier with wall coverage and double-sealed seams ($4,925–$6,725 total)
Crawl Space Drainage $4,025–$7,175 Complex hillside systems with multiple interceptors and long discharge runs ($7,625–$14,325)
Crawl Space Waterproofing Cost detail → $4,025–$7,175 Hillside lots with long discharge runs or significant existing flooding ($7,625–$10,650)
Sump Pump Installation Cost detail → $1,600–$3,125 Battery backup pump ($2,250–$4,025) or full drainage system with sump ($4,025–$7,175)
Crawl Space Encapsulation Cost detail → $10,650–$13,000 Dehumidifier, closed-cell rim joist foam, and full premium scope ($15,675–$21,500)
Insulation Replacement $2,500–$5,825 Spray foam on the foundation walls instead of the floor, which Washington’s energy code gives no crawl space wall path and PSE’s rebate does not cover ($4,025–$8,075)
Mold Remediation $1,600–$4,025 Full-area remediation paired with encapsulation or drainage to fix the source ($5,825–$10,650 combined)
Basement Waterproofing $7,625–$16,125 Dual sumps, large dehumidifiers, and finish replacement ($17,925–$26,875)
Foundation Waterproofing $15,825–$40,050 Hillside lots with shoring, deep excavation, or difficult access (beyond $40,050)

Prices assume a damp 1,200 to 1,500 sq ft Seattle-metro crawl space with standard access, before Washington sales tax, which applies to the full contract price (10.55% in Seattle from October 1 to December 31, 2026). See the wet crawl space scopes and the cost drivers below for how your situation shifts these ranges.

Crawl space insulation cost. Replacing the insulation under the floor is the insulation replacement row above: $2,500 to $5,825 typical, and $4,025 to $8,075 for the closed-crawl approach with spray foam on the foundation walls. The typical range includes taking out and disposing of the old batts, new floor insulation to current code R-value and air sealing at the rim joists; it does not include the moisture fix that ruined the last insulation. It is the one part of a crawl space job a utility rebate can offset, depending on what heats the house (see the rebate question below). Crawl space insulation covers the work itself.

Crawl space cleaning cost. No range is published for crawl space cleaning, here or anywhere else on this site: the model these ranges are adjusted from has no cleaning row, so there is nothing to adjust. The figures that do exist cover parts of a clean-out: about $2,500 in the calculator for wet or rodent-damaged insulation that has to come out, and the insulation row above for replacing it. Sanitizing after rodents and sealing their way in are not in any range. Crawl space cleaning explains what the work involves; a written quote after an inspection is the price.

Want one service taken apart? 4 services have a full cost breakdown of their own — vapor barrier cost, crawl space waterproofing cost, sump pump cost and crawl space encapsulation cost — each with what the scope includes, what moves it within its range, and where it ends and the next, more expensive scope begins.

Modeled estimates, produced . Each range is this publisher’s Portland-metro editorial model multiplied by 1.05418, the ratio of the 2024 price parities the Bureau of Economic Analysis publishes for the Seattle-Tacoma-Bellevue and Portland-Vancouver-Hillsboro metropolitan areas, rounded to the nearest $25. They are not drawn from contractor quotes: none were collected for this market, and this site does not hold a database of them. How these figures are produced →

Citing these figures, or want them as data? The same ranges are published as a structured dataset with the scope, basis and review date on every row, plus CSV and JSON downloads and a suggested citation form: the Seattle Crawlspace Cost Index →

Is this for a house you are buying or selling? A range means something different mid-transaction, where the question is usually how much exposure sits behind one line of an inspection report. What an inspection finding does and does not establish, how to bound it as a buyer, and whether to repair before listing.

Already holding a quote? A range only tells you whether a number is unusual. What separates two bids is almost always scope and paperwork, not price — the crawl space bid checker runs a quote against the line items a scope should name and against what Washington law requires of the contractor and the paperwork. Not at that stage yet? Crawl space repair in Seattle covers what to check before you hire.

Water Under the House

Wet Crawl Space Repair Cost

A wet crawl space is rarely one line item. What it costs depends on where the water comes from and how far the fix has to go — from moving roof water away from the foundation, through a drain and sump, to a sealed crawl space built on top of working drainage. If water is under the house right now, start with the standing water diagnosis; after a flood, what to do first comes before any of these prices.

The scopes, and what each costs

Each band is built only from rows and add-ons already published in the table above, for the same reference project — 1,200 to 1,500 square feet of crawl space floor, damp but without standing water at the time of the quote, reached through a standard exterior or interior hatch with roughly 3 feet of working clearance — so it carries every assumption and limitation on the methodology page.

Wet crawl space repair scopes and their modeled 2026 Seattle-area cost before sales tax, composed from the published price rows
Scope Built from Modeled range Fits when
Keep roof and surface water away Exterior downspout rework or regrading $700–$2,250 Quoted on its own, separately from any interior drainage. Often the first thing to try. Water shows up during and just after storms, then recedes; downspouts empty beside the foundation or the ground slopes toward the house.
A sump pump where drain lines already feed a basin Sump Pump Installation $1,600–$3,125 With a battery backup pump: $2,250 to $4,025. A drain already collects water to a low point, but the pump is missing, undersized or has failed.
Drain, sump and ground cover as one scope Crawl Space Waterproofing $4,025–$7,175 This is the crawl space waterproofing row: interior perimeter drain, sump and discharge, crack repair where cracks are the entry path, and a vapor barrier. Hillside lots with long discharge runs, or a space that already floods: $7,625 to $10,650. Water seeps in at the footing through the wet season. A common answer for a crawl space that is wet all winter.
Interior drainage plus a curtain drain uphill Crawl Space Drainage + Curtain drain on a hillside lot $6,275–$12,550 Complex systems with several interceptors and long discharge runs are priced as the drainage row’s premium band, $7,625 to $14,325. A hillside lot where groundwater moves downhill toward the house and the interior drain alone cannot keep up.
Drainage first, then a sealed crawl space Crawl Space Drainage + Crawl Space Encapsulation $14,675–$20,175 The encapsulation row excludes drainage and says it comes first, so the two are added. The liner replaces a separate vapor barrier, so none is added. Liquid water is getting in, and you want the space closed and conditioned rather than vented.
Drainage, a sealed crawl space and a dehumidifier Crawl Space Drainage + Crawl Space Encapsulation + Crawl space dehumidifier, supplied, installed and wired $16,025–$22,875 Supply air from an accessible furnace is sometimes the cheaper conditioning method; the dehumidifier figure includes the electrical work to feed it. As above, with a dehumidifier as the conditioning method.

Then, if the water has already done damage

Found at inspection and added on top of whichever scope fits. Never pre-summed here, because a wet crawl space may need none of these, one, or all three, and only someone under the house can say which.

  • Insulation Replacement $2,500–$5,825 Wet or collapsed batts out, new insulation in.
  • Mold Remediation $1,600–$4,025 Containment, removal and treatment of affected framing.
  • Wood rot repair, per location $375–$1,350 One bay, post or section of sill; not a structural repair range. For joists, girders and posts, see crawl space structural repair.

How these were put together

  • Bands are added only where the rows say the parts are separate jobs. The encapsulation row excludes drainage and says it is priced separately, so drainage plus encapsulation is a sum of two published rows. Where one row already names another’s work — crawl space waterproofing includes a vapor barrier — that row is used as it stands and nothing is stacked on it, because stacking would price the barrier twice. The build refuses a bundle that breaks this rule.
  • A sum is this page’s arithmetic, not a separately modeled figure. It prices each part as if bought on its own. One crew doing both in one mobilization may quote below the sum, and a quote that does is not thereby suspicious.
  • Drainage and crawl space waterproofing share a band on purpose. The methodology treats them as overlapping scopes built around the same drain-and-sump core, and the crawl space waterproofing cost breakdown explains how to tell which one a quote is actually for.
  • The ground cover matters even under a drain. A drain moves liquid water; it does nothing about moisture evaporating from bare soil. If a drainage quote leaves the soil uncovered, ask whether a ground cover is meant to follow and on what terms: the vapor barrier cost breakdown shows what a properly terminated standalone barrier involves, and the encapsulation cost breakdown what sealing the whole space adds.

How size and water move the price

The reference project is a mid-sized crawl space that is damp when the contractor looks at it. Change either and the calculator on this page changes the number, in two different ways: size scales the whole band, while water standing at the time of the quote adds a flat amount for the extra preparation. The table below is exactly what the calculator returns for its “Waterproofing” option — the drain, sump and ground cover scope — with every other answer at the reference setting: easy access, insulation in good condition, one to three months out.

Calculator output for the drain, sump and ground cover scope by crawl space size and water condition
Crawl space size Size vs reference Damp, some moistureWet, pooling waterStanding water present
Under 500 sq ft ×0.58 (42% below) $2,300–$4,200$3,100–$4,900$4,100–$6,000
500–1,000 sq ft ×0.77 (23% below) $3,100–$5,500$3,800–$6,200$4,900–$7,300
1,000–1,500 sq ftReference project ×1.00 (the reference size) $4,000–$7,200$4,800–$7,900$5,800–$9,000
Over 1,500 sq ft ×1.23 (23% above) $5,000–$8,800$5,700–$9,600$6,800–$10,600
  • Why the reference row reads slightly differently from the table above. The calculator rounds to the nearest $100, so the published $4,025–$7,175 displays as $4,000–$7,200. That rounding is the only difference, and a build-time check fails the release if it is ever more.
  • The size brackets are coarse. There is no bracket above 1,500 sq ft, so a 2,500 sq ft crawl space gets the same multiplier as a 1,600 sq ft one. Well beyond 1,500 sq ft, treat the last row as a starting point, not an answer.
  • Area is a proxy for drainage. A perimeter drain follows the walls, not the floor, so a long, narrow footprint has more trench to dig than a square one of the same area. That is one reason two same-sized crawl spaces can be quoted differently for identical work.
  • Access and old insulation add on top. Under 18 inches of clearance adds about $900, and wet insulation that has to come out first adds about $2,500, to any cell in the table.

Want the figure for your own crawl space? Run the calculator below with your size and conditions, or open the full-page cost calculator, which also explains how every adjustment is applied.

Cost Drivers

What Actually Moves the Price

These are the specific conditions that shift a quote up or down, with the dollar amount each one typically adds — the same adjustments the calculator applies, read from the same file, so this list and the calculator cannot disagree.

  • Square footage : Every range prices a 1,200 to 1,500 sq ft crawl space. The calculator scales the whole band for other sizes: about 42% lower under 500 sq ft, 23% lower at 500 to 1,000 sq ft, and 23% higher over 1,500 sq ft. It has no bracket above that, so a much larger space runs higher still.
  • Crawl height and access : Tight clearance adds roughly $450 in labor time; very low clearance, under 18 inches, adds roughly $900.
  • Standing water or moisture level : The ranges already price a damp crawl space, so damp and dry conditions add nothing. Water pooling at the time of the quote adds about $725, and standing water about $1,800, for the extra preparation before the main scope can start.
  • Insulation removal : Wet or rodent-damaged insulation that must be torn out and disposed of adds about $2,500; a crawl space with no existing insulation at all adds about $1,250.
  • Scheduling : An emergency start adds about $550 and a start within two weeks about $175, because a crew has to be moved off other work. Booking one to three months out, or planning ahead, adds nothing.
  • Discovered rot : Wood rot found on joists or rim boards once the old barrier or insulation comes out adds $375 to $1,350 per repair location. It cannot be seen until the space is opened up, which is why it can change a firm quote after work starts.
  • Vapor barrier grade : Washington’s code names 6-mil black polyethylene for the ground cover in a vented crawl space and no thickness above it, so heavier sheet is a durability choice, not a compliance one. A premium 20-mil cross-laminated barrier with wall coverage brings the vapor barrier line item to $4,925 to $6,725, against $3,400 to $4,675 typical.
  • Dehumidifier : A crawl space dehumidifier with the electrical work to run it adds $1,350 to $2,700 to an encapsulation project; supply air from an accessible furnace is sometimes the cheaper conditioning option instead.
  • Rim joist spray foam : Closed-cell spray foam at the rim joists adds $1,075 to $2,150 to an encapsulation project.
  • Hillside lots and drainage complexity : A curtain drain to intercept water moving downhill toward the house adds $2,250 to $5,375 to a drainage scope, and complex systems with several interceptors and long discharge runs reach $7,625 to $14,325 in total.

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, pipe, gravel and whatever comes out 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 a 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

Two code requirements decide how much of a crawl space job is optional. First, 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. A ground cover is therefore the code’s baseline for a vented crawl space, not an upgrade. Second, a sealed crawl space is a larger job here than the word suggests: 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 bids that differ on those are not pricing the same work.

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: an electrical permit is needed whenever wiring is installed, altered or extended, which covers a new circuit or receptacle for a sump pump 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

The utility rebates in this area pay toward insulation, air sealing and duct sealing, not toward a liner, sealed vents, a dehumidifier or drainage. 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.

Seattle Metro Context

Why Seattle Pricing Looks the Way It Does

Seattle’s rain is concentrated in the cool half of the year. At Seattle-Tacoma International Airport the 1991–2020 normal is 39.34 inches a year, and 75.4% of it falls between October and March; the Seattle Sand Pt WSFO station records 37.82 inches. Across the 8 stations this site publishes for the area, the annual normal runs from 33.37 inches at Everett Snohomish AP to 63.28 at Snoqualmie Falls, so the figure depends on where you are. Most of a year’s water arriving in six months is the physical reason drainage and moisture control dominate the table above, rather than the repairs a drier climate would prioritize.

The soil survey says less about Seattle itself than you might expect. USDA’s soil survey gives no drainage class to 87.1% of Seattle’s mapped area, most of it Urban land, so the city’s 0.3% share in the somewhat poorly to very poorly drained classes reflects unrated ground, not ground that drains well. Among the cities this site covers where the survey rates most of the ground, the highest shares in those wetter classes are Auburn (23.4%), Issaquah (19.7%), and Kent (19.2%). What the drainage classes do not capture is glacial till, known locally as hardpan: the City of Seattle’s landslide study describes it as very dense and relatively impervious, so water soaking down through the soil above it perches on top of it, and says that perched water normally dries up in spring or summer and returns in winter. Water that reaches a crawl space in those conditions tends to stay rather than soak away.

Housing age matters as much as the weather. In the City of Seattle 38.4% of housing units were built before 1960, and the median year built is 1976. An older crawl space is the one most likely to need a full retrofit rather than a partial fix: the ground cover, if there ever was one, has had decades to fail, and the insulation above it has had the same decades to get wet. The census figures cover every housing unit, apartments included, and say nothing about foundation type, so they describe the stock rather than any one house. Seattle crawl space repair by neighborhood shows where the oldest of that stock sits.

Licensing also shapes who can quote you a number in the first place. Washington requires every contractor to register with the Department of Labor & Industries (L&I), and bidding or working while unregistered is a gross misdemeanor. Two different parts of Washington’s codes set the baseline, and they are worth keeping straight: Section R408 of the residential code governs the under-floor space itself — either a vented crawl space with a 6-mil black polyethylene ground cover, or a sealed one with a sealed Class I vapor retarder, a radon system and continuously running exhaust — while floor insulation values come from the state energy code, not R408. A quote that doesn’t meet the code baseline isn’t a bargain, it’s a project you’ll likely pay to redo.

Before You Sign

What a Proper Quote Should Include

A number without these details isn't a real quote yet - it's a guess. A registered contractor's written quote should include:

  • A written, line-item scope of work - not a verbal number or a one-line estimate.
  • Materials specified by name and spec: mil thickness on the vapor barrier, R-value on insulation, pump horsepower, not just "vapor barrier" or "insulation."
  • Your crawl space square footage and clearance height noted, since both directly drive labor time.
  • Labor and materials broken out separately, so you can see what you’re paying for.
  • The price with Washington sales tax stated, or a plain note that the total is before tax.
  • Permit status addressed if the scope requires one.
  • Warranty terms in writing, including what’s covered and for how long.
  • The contractor’s Washington L&I registration number, which L&I says belongs on the written bid, so you can verify it yourself before you sign.
  • No pressure to sign the same day the inspection happens.
Scope

Basic, Standard and Complex Projects

The spread across this table is mostly scope, not one contractor being expensive. It helps to think in three tiers rather than one number. The tiers overlap because the scopes do: a hillside drainage job can cost more than a flat-lot encapsulation.

Basic

$1,600 – $4,675

One defined problem, one defined fix, no excavation: a standalone sump pump, a standalone vapor barrier, a contained mold cleanup. Typically one to two days on site.

Standard

$4,025 – $13,000

Water management plus moisture control together: an interior perimeter drain with a sump, or a full closed-crawl encapsulation. Interior trenching, several days on site, and the tier a crawl space with both a water problem and a moisture problem lands in.

Complex

$7,625 – $40,050+

Hillside drainage with several interceptors, a whole-basement system, or exterior excavation of the foundation. Heavier equipment, possible engineering, landscape restoration afterward, and the tier where a second opinion is worth the delay.

Two quotes that differ by thousands are usually quoting different tiers. The included-and-excluded table is the fastest way to work out which one you are holding.

Reference

What These Figures Assume, and What They Leave Out

The project being priced

  • Size: 1,200 to 1,500 square feet of crawl space floor
  • Condition: damp but without standing water at the time of the quote
  • Access: a standard exterior or interior hatch with roughly 3 feet of working clearance
  • Building: a single-family home on a continuous perimeter foundation

Excluded from every range

  • Washington retail sales tax, which applies to the full contract price, labor and materials together, at the rate for the job site: 10.55% in Seattle from October 1 to December 31, 2026. Every range here is before tax
  • Permit fees, which vary by jurisdiction and are usually billed at cost
  • Structural repair of framing found to be rotten once the space is opened up
  • Asbestos or lead abatement, which is separate work no range here prices
  • Electrical service upgrades where an existing panel cannot carry new equipment
  • Landscape or hardscape restoration after exterior excavation

Per-service inclusion and exclusion lists, the definitions behind terms like “encapsulation” and “Class I vapor retarder”, the limitations of these figures, and the revision history are all on the cost methodology page.

Free Tool

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Answer six quick questions for an estimate built from the same pricing on this page, adjusted for your square footage, condition, access, and insulation. Prefer the full-page version? Open the standalone calculator →

Free Estimate Tool

Crawlspace Cost Calculator

Answer 6 quick questions for a modeled 2026 Seattle-area price range, before sales tax. How these figures are produced.

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Guides That Affect What You Pay

Sources

The climate, soil and housing-age figures come from this site's published climate and housing dataset, which cites these federal surveys; the hardpan description is from the City of Seattle's landslide study. The Washington residential and energy code sections, L&I's registration rules and the PSE, Snohomish County PUD and Seattle City Light rebate pages establish what a compliant scope has to meet, who may bid it, and what offsets part of it. The price-factor section adds Washington's sales tax law, the City of Seattle's stormwater, side sewer, building, electrical and plumbing permit rules, and the CDC's rodent clean-up guidance. Washington's insurance commissioner supports the coverage answer below. None of them prices this work — no published source does for this metro, which is why the ranges above are modeled rather than cited.

  1. NOAA National Centers for Environmental Information, U.S. Climate Normals (1991–2020) — Annual/Seasonal and Monthly (normals-annualseasonal-1991-2020, normals-monthly-1991-2020) Open dataset Checked

    Every precipitation figure in the Seattle-metro climate and housing dataset: annual and monthly precipitation normals, the October–March total summed from the monthly normals, the average number of days per year at or above 0.10, 0.50 and 1.00 inches, and the completeness flag and years of record NCEI publishes alongside each value, for the eight stations within 15 miles of a served city with at least 20 years of record (Snoqualmie Falls, Landsburg, Monroe, Tacoma #1, Seattle-Tacoma International Airport, Seattle Sand Point, Renton Municipal Airport and Everett Snohomish County Airport). Pulled through the NCEI data access service on 2026-11-10.

    Note: A normal is a 30-year statistic for one instrument at one point, not a value for the surrounding city. NCEI publishes a completeness flag with every value and this site republishes it, because a station with 20 years of record and one with 29 are not equally strong evidence. Seattle Boeing Field has 19 years behind its annual normal and is not published.

  2. USDA Natural Resources Conservation Service, Soil Survey Geographic Database (SSURGO), via Soil Data Access (muaggatt.drclassdcd — drainage class, dominant condition) Open dataset Checked

    The soil drainage columns for the 19 cities in the Seattle-metro climate and housing dataset: the share of each city’s mapped area whose dominant soil drainage class is somewhat poorly drained, poorly drained or very poorly drained, and the share carrying no drainage class at all. Computed on 2026-11-10 by intersecting each Census place boundary with the SSURGO map units of the King County Area, Snohomish County Area, Pierce County Area, City of Seattle, City of Tacoma and Mount Baker-Snoqualmie National Forest survey areas and area-weighting the result; the survey-area versions were read on 2026-11-11.

    Note: SSURGO assigns no drainage class to Urban land map units or to water. In Seattle, Shoreline and Burien more than four fifths of the mapped area is unrated Urban land, so their wetter-class shares are near zero because the ground is unrated, not because it drains well, and they are not compared with the other cities. Drainage class also describes natural soil in place — not the fill, the grading or the downspout run at any individual house.

  3. Seattle Public Utilities (prepared by Shannon & Wilson), Seattle Landslide Study, Volume 1 Checked

    That Vashon till, known locally as “hardpan”, is very dense and relatively impervious, so water soaking down through the deposits above it normally perches on top of it; that the contact between recessional outwash and till is normally less than 10 feet deep and the water perched there normally dries up in spring or summer and returns in winter; that the boundary where groundwater perches on the Lawton Clay is commonly termed “The Contact”; and that the study’s database holds 1,326 landslides reported through June 1999, records going back to 1890, about 84 percent with some human influence, landsliding in only about 1 percent of the city, and the highest densities in Southwest Magnolia, Southwest Queen Anne, Madrona, Interlaken and Alki.

    Note: The PDF prints no date; 2000 is the year Seattle Public Utilities gives for it. A 2003 update added about 110 landslides; this site quotes the original figures.

  4. 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.

  5. Washington State Legislature, RCW 18.27.020 — Registration required; prohibited acts; criminal penalty Checked

    That every contractor must register with L&I, and that it is a gross misdemeanor to advertise, offer to do work, submit a bid or perform work as a contractor while unregistered or while the registration is suspended or revoked, or to subcontract to or use an unregistered contractor.

  6. Washington State Department of Labor & Industries, Register as a Contractor Checked

    That Washington requires every construction contractor to register with L&I and to be bonded and insured; that there are two classifications, general and specialty, with 63 specialties; that a specialty contractor works only in the registered specialty and cannot hire subcontractors; that plumbing, electrical, elevator, mobile home installation, boiler and asbestos work carry further education, examination and licensing requirements; the bond amounts ($30,000 general, $15,000 specialty); the liability insurance L&I asks for ($200,000 public liability and $50,000 property damage, or $250,000 combined single limit); that the bond and insurance must carry the exact business name; and that L&I suspends a registration when a bond or insurance policy lapses or a judgment goes unsatisfied.

    Note: L&I’s page for contractors. The statute states the insurance minimums differently (RCW 18.27.050); this site gives both.

  7. Washington State Department of Labor & Industries, Hire Smart Step-by-Step Checked

    L&I’s own advice to homeowners: that the registration number is found in a contractor’s advertisements and on the written bid, and that the law requires it in all advertisements, business cards and internet advertising included; that a contractor with workers on the job must have an active, up-to-date workers’ comp account, which Verify shows, and that an owner-operator with no employees is not required to have one; that a contract should state the price including sales tax, payment terms, permit fees, the specific work, materials and subcontractors, warranties and the change-order process; that in most cases the contractor, not the homeowner, takes out the permits; that a construction lien may be filed within 90 days of work stopping or materials being delivered; and that a homeowner should ask for lien releases before the final payment.

    Note: Guidance, not statute. The contract contents are L&I’s recommendation; this site found no Washington statute that requires a written residential construction contract.

  8. 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.

  9. Washington State Building Code Council (via Washington State Legislature), WAC 51-11R-40213 — Table R402.1.3, Insulation minimum R-values and fenestration requirements by component (2021 Washington State Energy Code, Residential) Checked

    The floor insulation value for new construction: R-30, in a table with a single column for Climate Zone 5 and Marine 4, which covers the whole state. The table’s columns are fenestration, skylight, ceiling, wood frame wall, floor, below-grade wall and slab; there is no crawl space wall column. Footnote a: insulation installed in a cavity shallower than its label thickness counts at its compressed R-value.

  10. Washington State Office of the Insurance Commissioner, Leaks, water damage and mold Checked

    That homeowner insurance usually provides limited mold coverage only where the mold results from a covered loss; and that gradual leaks are typically not covered, including a leaking foundation, cracks in walls, groundwater seeping in, and damage that develops over more than a couple of days. Also that sudden and accidental leaks, burst pipes included, and frozen pipes where the home was properly heated, are usually covered if reported quickly and repaired as the insurer recommends; and the commissioner’s Consumer Advocacy line, 800-562-6900.

    Note: Washington’s insurance regulator, describing typical policies in general terms; it publishes no typical dollar limit for mold coverage, and the policy wording decides any one claim.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  21. 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.

  22. 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.

  23. 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.

  24. 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.

  25. 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.

  26. 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.

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