Are there termites in Washington?
Yes. Washington State University Extension’s Pestsense fact sheet names two native termites: the dampwood termite and the subterranean termite. Its longer bulletin identifies them as the Pacific dampwood termite (Zootermopsis angusticollis) and the western subterranean termite (Reticulitermes hesperus), says both occur on both sides of the Cascades, and calls termites among the most important structural insect pests in the Northwest, with only carpenter ants rivaling them.
The same bulletin draws a line that matters for this area: in western Washington, it says, the subterranean termite occurs only as far north as Seattle. That puts the cities north of Seattle this site covers, from Shoreline to Everett, outside the subterranean termite’s range as the bulletin described it, though it is a 2002 publication and not a survey of where infestations are found today. No agency publishes a count of infested houses, and nothing here guesses at one.
Dampwood or subterranean: which one is under your house?
They look alike to most people and behave very differently, and the difference tells you what is wrong with the crawl space.
| Pacific dampwood termite | Western subterranean termite | |
|---|---|---|
| Where it lives | Inside wet or rotting wood; it does not nest in dry, sound wood | In the soil, travelling to wood sources |
| Size and color | The largest termite here: winged adults orange-brown, about 3/4 inch including wings; workers whitish, about 1/2 inch | Winged adults black, about 3/8 inch including wings; workers grayish white, about 1/4 inch |
| When winged ones appear | Late summer or fall, especially after rain | Any time of year, per WSU’s fact sheet; mainly fall in western Washington, per its older bulletin |
| The tell-tale sign | Wood that is wet or decaying where they are found | Mud tubes on the foundation, and damage inside sound wood |
| What it says about the crawl space | A prior moisture problem: wood-soil contact, a leak, framing that has been damp for a long time | A path from soil to wood; this one commonly attacks sound wood and can be very damaging |
| Usual fix | Correct the conditions; WSU says pesticides are rarely needed | Professional treatment; WSU says chemical control is usually the only option once established |
The practical conclusion follows from the first row. Dampwood termites in a house are living in wood that is already wet and probably decaying, so their colony is the second problem, not the first. Subterranean termites are the one case where the insects can be the first problem, because they bring their own moisture from the soil and do not need the wood to be wet.
What are the signs of termites in a crawl space?
Termites are hard to see, because they work inside the wood. The USDA Forest Products Laboratory’s Wood Handbook notes that subterranean termites tunnel along the grain and leave a shell of sound wood over their galleries, so damage seldom shows on the surface. What to look for with a good light:
- Mud tubes. Tunnels of soil running up the stem wall, a pier or a post. The Wood Handbook calls them a good indicator of subterranean termite activity; check both faces of the foundation.
- Wood that gives under a probe. Because the damage is hidden, the handbook advises probing suspect wood with a pick or knife.
- Wet or decaying wood with insects in it. This is where dampwood termites live: a rotted sill under a leaking toilet, a post end sitting on wet soil, framing near a long-running plumbing leak, or old form boards left in the dirt.
- Shed wings and swarmers. Winged termites, or piles of their dropped wings, near the crawl space or coming from the house rather than the yard.
- Sawdust piles. Not termites, usually: WSU says the best sign of a carpenter ant infestation is the sawdust they excavate from their tunnels (see below).
A finding in the yard is not a finding in the house. WSU’s advice is to contact a pest management professional when termites are coming from inside or under the house; a stump in the garden full of dampwood termites is a reason to remove the stump.
Termite, carpenter ant or wood-boring beetle?
Four groups of insects turn up in wood under houses here, and telling them apart changes who you call.
- Carpenter ants do not eat wood. WSU’s bulletin says they remove wood to enlarge their nests, and that hollowed-out main beams can become unsafe. They are 1/4 to 1/2 inch long, black or red and black, and the species most common in Washington houses, Camponotus modoc, is black with reddish legs. They also nest in insulation; WSU’s bulletin shows them under the insulation in a crawl space. Many home infestations are satellite nests of a parent colony outside, in a stump, log or woodpile, and that parent colony needs a moisture source such as wood in contact with soil or damp areas in crawl spaces. In a crawl space, WSU suggests tapping the joists: a nest cavity gives a hollow ring.
- Moisture ants are small, usually light yellowish-brown, and nest in damp rotting wood or soil, never in dry, sound wood. WSU calls them an indicator of a prior problem such as wood-soil contact.
- Deathwatch (anobiid) beetles are reddish to chocolate brown and 1/8 to 1/4 inch long, and rarely seen; the sign is fresh piles of gritty, granular dust on joists and sills. WSU says their larvae feed in softwoods such as Douglas fir for 4 to 5 years, in crawl spaces with wood moisture around 14 to 17 percent, and can hollow out posts, joists and sill plates. They are a problem where crawl spaces are poorly vented and vapor barriers are missing or in disrepair.
- Termites eat the wood, and are told from ants by their straight antennae and thick waist; ants have elbowed antennae and a pinched waist.
Why moisture decides whether termites stay
Every source read for this page comes back to water. WSU says the dampwood termite lives and feeds in wet or rotting wood and needs a high moisture level to become established: wood-soil contact, wood saturated by leaky pipes or poor gutters, or beams damp from poor ventilation. The Wood Handbook says subterranean termites dry out easily and need a constant source of moisture, and that the hazard is greatest in a crawl space that is poorly drained and has no moisture barrier on the soil. WSU’s carpenter ant bulletin says moisture in poorly ventilated crawl spaces feeds wood-decay fungi and makes ideal carpenter ant habitat, and strongly encourages vapor barriers in crawl spaces.
The Wood Handbook’s description of a crawl space that resists termites reads like a crawl space repair scope:
- wood floor joists at least 18 inches and girders at least 12 inches above the soil;
- a polyethylene vapor barrier over the exposed soil, carried partly up the foundation wall;
- rain and roof water carried away from every side of the house with gutters, downspouts and grading;
- posts that bear directly on the ground made of concrete, not wood;
- concrete forms, stakes, stumps and scrap wood removed from under the house.
Two of those points are in Washington’s code too. R408.1, in WAC 51-51-0408, requires a 6-mil black polyethylene ground cover over crawl space soil, and the unamended R408.5 requires the ground under a house to be cleared of vegetation and organic material, with forms and construction materials removed. WSU’s dampwood termite advice is the same idea in one line: remove form wood left in the soil around the foundation and keep a ventilated crawl space with a vapor barrier in place.
That is why a termite find in a crawl space so often comes with other findings: a torn or missing ground cover, a damp corner by a downspout, decay in the sill. If the space is damp, what high humidity in a crawl space means covers readings and causes, and if the wood itself is soft, how serious wood rot in a crawl space is explains how decay and insects travel together.
What does fixing termites in a crawl space involve?
Three jobs, usually done by different people, and the order matters: stop the water, deal with the colony, then repair the wood once it can stay dry.
- Find and stop the water. A plumbing leak, a missing or torn ground cover, water draining toward the foundation, wood touching soil. The Wood Handbook lists repairing leaks that keep wood wet, such as plumbing leaks, as one of the ways to control termites already in a building, and for dampwood termites WSU says correcting the conditions is usually enough.
- Break the soil-to-wood contact and deal with the colony. The handbook describes blocking the runways from soil to wood and treating the soil. For subterranean termites WSU says chemical control is usually the only option once established, and to call a pest management professional for termites coming from inside or under the house.
- Repair or replace the damaged wood, once it can stay dry. A rotted sill, a post end, a joist bearing: framing that has lost strength gets replaced, and posts that sat on soil go onto concrete.
- Keep inspecting. The handbook’s guard against reinfestation is frequent inspection for signs of activity. A look under the house once or twice a year is part of the seasonal crawl space checklist.
Step 1 and step 3 are the crawl space work: vapor barrier installation for bare or torn ground cover, crawl space drainage where water reaches the foundation, and crawl space structural repair for joists, sills, posts and girders the insects have weakened.
Who does which part?
| The job | Who does it | What to check |
|---|---|---|
| Identifying the insect, treating the soil or wood, baiting or removing the colony | A pest control company | A commercial pesticide applicator license from the Washington State Department of Agriculture. |
| A wood destroying organism inspection for a sale or refinance | A WSDA-licensed structural pest inspector | The inspector’s structural pest inspector license with WSDA. |
| Leaks in supply or drain lines | A plumber | L&I registration, and the plumber’s certification. |
| Bare or torn ground cover, water reaching the foundation, damp framing | Crawl space vapor barrier and drainage work | L&I contractor registration. |
| Replacing joists, sills, posts or girders the insects or decay have weakened | Crawl space structural repair | L&I contractor registration; an engineer where the load path changes. |
On the pest control side, Washington law requires anyone in the business of applying pesticides to someone else’s property to hold a commercial pesticide applicator license from the Department of Agriculture. Public Health — Seattle & King County’s advice for choosing a pest control company applies to insects as well as rodents: ask to see the license, ask about integrated pest management, which often uses less poison, and be clear in writing about what you want done.
On the construction side, anyone contracting for the moisture and framing work must be registered with Washington’s Department of Labor & Industries, bonded and insured; how to verify a Washington contractor explains the check. If you want the moisture and the framing looked at, you can request a free in-home inspection. The written quote should say which wood is damaged, what is keeping it wet and how that will be stopped; treating the insects stays with a licensed pest control company.
Termites when buying or selling a house
In Washington, a wood destroying organism inspection made as part of a sale, exchange or refinance has to be a complete inspection by someone holding the state’s Structural Pest Inspector license, and the rules require the crawl space to be inspected where it is accessible, or the report to say why it was not and that the area may be vulnerable. A home inspector who is not also a licensed structural pest inspector may report rot and conditions conducive to wood destroying organisms, but must refer the identification of insects to a licensed inspector. Some government-backed loans also ask about wood-destroying insects, which the FHA and VA crawl space requirements set out. For what an inspector’s note about insects or decay does and does not establish, see crawl space problems found in a home inspection.
Insurance rarely enters into it. Washington’s Office of the Insurance Commissioner says homeowner policies usually do not cover rot unless it results from covered water damage, and that gradual leaks are typically not covered.
Photo credits: Pacific dampwood termite by Judy Gallagher, CC BY 2.0; western subterranean termite by Ken-ichi Ueda, CC BY 4.0; both cropped, the first rotated. Crawl space access photo: Kathleen Austin Kuhn, Pexels.
Sources
Species, sizes, signs and control positions are Washington State University Extension’s and the USDA Forest Products Laboratory’s; licensing is from RCW 17.21.070, chapter 16-228 WAC and RCW 18.280.190; the insurance line is Washington’s Office of the Insurance Commissioner; code text is WAC 51-51-0408 and the unamended R408.5 in Seattle’s 2021 residential code. No pesticide product or treatment is recommended here, and no one from this site has seen your crawl space.
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Washington State University Extension, Termites (Pestsense fact sheet) Checked
That the two native termites in Washington are the dampwood termite and the subterranean termite; that the dampwood termite lives and feeds in wet or rotting wood, does not nest in dry sound wood and is an indicator of a prior problem such as wood-soil contact; that it is the largest termite, winged forms orange-brown and about 3/4 inch with wings, workers whitish and about 1/2 inch; that subterranean termite swarmers are black and about 3/8 inch with wings, workers grayish white and about 1/4 inch, and that this termite lives in the soil, commonly attacks sound wood and can be very damaging; that dampwood termites swarm in late summer or fall, especially after rain, while subterranean termites may swarm any time of year; that pesticides are rarely needed for the dampwood termite, whose prevention is removing form wood from the soil and keeping a ventilated crawl space with a vapor barrier; that there are no reliable non-chemical prevention techniques for subterranean termites; and to contact a pest management professional for termites coming from inside or under the house.
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Washington State University Cooperative Extension, Termites: Biology, Prevention, and Control (Extension Bulletin EB0787 (2002 reprint)) Checked
That termites are among the most important structural insect pests in the Northwest, rivaled only by carpenter ants; that the Pacific dampwood termite needs a high moisture level to become established, such as wood-soil contact, wood saturated by leaky pipes or poor gutters, or beams damp from poor ventilation; that in western Washington the western subterranean termite occurs only as far north as Seattle, swarms mainly in the fall there and lives in the soil, so damp wood is not essential to it; and that chemical treatment is essential for subterranean termites, while dampwood termites are usually eliminated by correcting the conditions.
Note: A 2002 reprint, read for the Seattle-area dossier on 2026-11-10. Its northern-limit statement for the subterranean termite is the only range statement found in a primary source; it is not a survey of where infestations occur today.
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USDA Forest Products Laboratory, Wood Handbook, Chapter 14: Biodeterioration of Wood (General Technical Report FPL-GTR-282 (2021 edition)) Checked
The wood moisture content and temperature ranges at which decay fungi become active, which is what separates a surface mold problem from structural rot. Also, for the white-mold guide: mold shows as fuzzy or powdery surface growth in colors from light shades to black, and on softwoods can often be brushed off (p. 14-2); mold and stain fungi affect strength only slightly but make wood more absorbent, which can lead to decay (p. 14-2); fresh surface growth of decay fungi can look like fan-shaped patches, strands or root-like structures, usually white or brown (p. 14-3); white rot leaves wood bleached and spongy, brown rot darkens it and cracks it into cubes, and some brown-rot fungi form water-conducting strands that carry soil water into dry wood (p. 14-4); and that crawl-space condensation, whose primary source is soil moisture, can cause serious decay, while wood debris and concrete forms left under a building can seed it (p. 14-7). And, for the termite guide (pp. 14-11 to 14-15): anobiid powder-post beetles generally need wood at about 15% moisture or more, which inadequate ventilation can create and lower moisture through ventilation, insulation and vapor barriers can relieve; subterranean termites need a constant source of moisture, build mud shelter tubes that are a good sign of their activity, swarm usually in early spring or fall, and leave galleries along the grain under a shell of sound wood, so suspect wood is probed with a pick or knife; infestation hazard is greatest over a crawl space that is poorly drained and lacks a moisture barrier; in a crawl space, joists at least 18 inches and girders 12 inches from the earth, a polyethylene barrier over the soil running partly up the foundation wall, drainage away from the house with gutters, downspouts and grading, posts that bear on the ground made of concrete, and concrete forms, stakes, stumps and waste wood removed; control of termites already in a building means breaking the contact between the soil colony and the woodwork by blocking runways, treating the soil, repairing leaks such as plumbing leaks, or a combination, then inspecting often; carpenter ants use wood for shelter rather than food, prefer wood softened by decay and so can point to a moisture problem, and species such as Camponotus modoc can be particularly damaging.
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Washington State University Extension, Carpenter ants (Pestsense fact sheet) Checked
That carpenter ants are 1/4 to 1/2 inch long, black or red and black; that they do not eat wood but excavate it for nesting and occasionally cause structural weakening, and also nest in insulation; that many home infestations are satellite nests of a parent nest outside, which has the queen and is usually in a stump or log; that mating swarms generally occur from April to early June; and the advice to keep shrubbery and branches off the house and remove stumps and rotting logs near it.
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Washington State University Extension, Carpenter Ants: Their Biology and Control (Extension Bulletin EB0818, revised January 2005) Checked
That most carpenter ant problems in Washington come from Camponotus modoc and C. vicinus, and C. modoc, black with reddish legs, is the most common in houses; that the ants do not eat wood but remove it to enlarge their nests, and hollowed-out main beams can become unsafe; that the best sign of an infestation is the sawdust they push out of their tunnels; that in a house with a crawl space the joists can be tapped to find the hollow ring of a nest cavity, where a knife blade will usually go in; that the parent colony needs a moisture source such as wood in contact with soil or damp areas in crawl spaces; that moisture in poorly ventilated crawl spaces feeds wood-decay fungi and makes ideal carpenter ant habitat; that soil should be kept away from sill plates; and that vapor barriers in crawl spaces are strongly encouraged.
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Washington State University Extension, Moisture ants (Pestsense fact sheet) Checked
That moisture ants are small, usually light yellowish-brown, nest in damp rotting wood or soil and not in dry sound wood, and are an indicator of a prior problem such as wood-soil contact; and that prevention is avoiding wet wood and keeping a ventilated crawl space with a vapor barrier in place.
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Washington State University Extension, Deathwatch beetles (Anobiids) (Pestsense fact sheet) Checked
That anobiid (deathwatch) beetles are reddish to chocolate brown and 1/8 to 1/4 inch long, rarely seen, and that fresh piles of granular or gritty frass on joists and mudsills are the sign of them; that the larvae feed in wood for 4 to 5 years, preferring softwoods such as Douglas fir; that they are found in crawl spaces with wood moisture content around 14 to 17 percent and can hollow out pier posts, joists and sill plates; that they are a problem where crawl spaces are poorly vented and vapor barriers are missing or in disrepair; and that the fixes are cross ventilation, an intact vapor barrier and replacing localized infested lumber after professional advice, with no pesticide recommended for homeowner use.
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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 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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Washington State Legislature, RCW 17.21.070 — Commercial pesticide applicator license Checked
That engaging in the business of applying pesticides to someone else’s land requires a commercial pesticide applicator license, which is a Department of Agriculture license separate from contractor registration.
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Public Health — Seattle & King County, Preventing rodents and keeping them away Checked
That in King County it is the property owner’s responsibility to prevent conditions on the property that attract rodents; the advice to check inside and outside the house for gaps and holes; and that the department points to CDC’s guidance for cleaning up after rodents rather than publishing its own. Also, read 2026-11-11: that the best trap indoors is the wooden snap trap baited and set near droppings, and poisons are not recommended for rat control inside buildings because poisoned rats die in hard-to-reach places and smell; that firewood should be stacked 18 inches off the ground and bushes, vines and branches kept 3 feet from the house, since roof rats get in from branches over the roof; that heavy infestations may be too extensive to control alone and Public Health then recommends a professional pest control company, asking about integrated pest management; that some crawl space and attic companies also offer pest control; and that pest control companies should be licensed with the Washington State Department of Agriculture.
Note: King County only. Snohomish County’s health department does not run a pest program.
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Washington State Department of Agriculture, Structural Pest Inspector (SPI) License Checked
That in Washington the SPI license is required of anyone conducting complete wood destroying organism (WDO) inspections, those made to find evidence of infestation, damage or conducive conditions as part of the transfer, exchange or refinancing of a structure; that licensed home inspectors need it only when they include wood-destroying-insect inspections; and that the requirements are in chapter 15.58 RCW and WAC 16-228.
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Washington State Legislature, RCW 18.106.020 — Plumbers: certificate or permit required Checked
That nobody may engage in the trade of plumbing without a plumber’s certificate or permit, and that a contractor may employ a person to do plumbing only if the contractor is a licensed plumbing contractor and the person holds a certificate.
Note: This site has not established whether setting a sump basin and a discharge line that does not join the building drain counts as plumbing under the chapter. Ask the plumbing permit office for the address.
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Washington State Department of Agriculture (via Washington State Legislature), Chapter 16-228 WAC, sections 2005 to 2060 — Wood destroying organism inspections Checked
That a wood destroying organism (WDO) inspection done for the sale, exchange or refinancing of a property must be a complete WDO inspection by a licensed individual; that substructure crawl areas must be inspected when accessible, and where they are not the report must say why and state that the area may be vulnerable and should be made accessible; that a specific WDO inspection must accompany any proposal or estimate to prevent or control WDOs, may be done only by a licensed structural pest control operator or structural pest inspector, and may not stand in for a complete inspection in a sale.
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Washington State Legislature, RCW 18.280.190 — Home inspectors: structural pest inspector Checked
That a home inspector who is not also a licensed structural pest inspector may refer in the report only to rot or conditions conducive to wood destroying organisms, and must refer the identification of, or damage by, wood destroying insects to a licensed structural pest inspector.
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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.
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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.
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.