Termites exist in western Washington but are generally considered less common than in warmer states, and no local count is available. WSU describes two native types: dampwood termites in wet or rotting wood, and subterranean termites in soil. Damp wood, carpenter ants and decay are the more likely causes of wood trouble in a Seattle house.
Key takeaways
- Two kinds of termite are native to Washington, according to WSU: dampwood termites, which live in wet or rotting wood, and subterranean termites, which live in the soil and reach wood through tunnels.
- No count of termite infestations for Seattle or any neighborhood is available, and the pest trade in western Washington often describes termites as less common here than in warmer states, so treat the risk as modest and not zero.
- Dampwood termites swarm in late summer or fall, especially after rain, while subterranean termites may swarm in any month, so a winged insect indoors needs identification, not assumption.
- For dampwood termites the main remedy is moisture control: remove infested wood, keep wood off the soil, ventilate crawl spaces and do not stack firewood against the house. WSU says pesticides are rarely needed.
- A wood-destroying organism inspection in Washington is done by a licensed structural pest inspector. Ask for the licence details, and confirm them with the state, before relying on a report.
Which termites live in western Washington?
Two native types, according to WSU PestSense. Dampwood termites live in wet or rotting wood and need moisture. Subterranean termites live in soil and travel to wood through mud tubes. They differ in habits, swarm timing and the way they are controlled, so identification comes before any plan.
Dampwood termites are the type most tied to this climate. They are attracted to wood with high moisture content: a rotted fence post, a buried form board, a stump, a log pile, a leaking sill. A colony needs the wet wood to survive.
Subterranean termites nest in the soil and need contact with it. The winged forms are about three-eighths of an inch and may swarm at any time of year. WSU notes there is no reliable non-chemical prevention for them, which is a reason to take an inspection seriously if mud tubes are found.
The sections that follow set out how to tell termites from ants, what an inspection involves and what to do about each type. The short version is that damp wood decides most outcomes, and a calm, evidence-based look at your own building is better than worry or complacency.
| Feature | Dampwood termites | Subterranean termites |
|---|---|---|
| Where they live | Wet or rotting wood | In the soil, reaching wood through tunnels |
| Swarm timing | Late summer or fall, especially after rain | May swarm in any month |
| Role of moisture | Essential; they need wet wood | Soil contact is the essential link |
| Usual control | Remove infested wood and fix moisture; pesticides rarely needed | No reliable non-chemical prevention; treatment plans are usually considered |
| First clue to look for | Soft, wet wood and pellets | Mud tubes on foundation walls or in crawl spaces |
How common are termites in Seattle?
Less common than in warmer states, according to a general view in the pest trade, but there is no count for Seattle or any neighborhood and no source here ranks them. Treat the risk as modest and tied to damp wood. An inspection is the way to know about one building, and a sale is a common reason to have one.
It is tempting to give a number, and we do not have one. Instead, two honest points. First, termites are a fixture of home sales in parts of the country where they dominate the pest picture, and that fear is partly imported. Second, the lack of local figures is a gap, not proof of absence.
What an inspector more often finds in a Seattle house is moisture, decay, carpenter ants and moisture ants. These are the problems the same damp that suits dampwood termites also creates.
Why do swarms follow the rain?
WSU PestSense says dampwood termites swarm in late summer or fall, especially after rain. Rain raises humidity and softens the ground and wood, which suits winged adults leaving to start new colonies. A swarm shows a colony somewhere nearby, which may be a stump, a log, a fence or a neighbor's property, not necessarily your house.
One or two winged insects outdoors is a smaller signal than a dozen on a sill, with wood in the room that you know is damp. If you see many, capture a few in a jar, note the date and weather, and call.
Do not treat the swarm with a household spray. Swarmers die soon after emerging, and the specimen is more useful for identification than a dead cloud of them.
Termites, ants or something else?
Check the waist, antennae and wings. Ants have a pinched waist, elbowed antennae and forewings longer than hind wings; termites have a thick waist, straight beaded antennae and wings of equal length. Carpenter ants swarm in April to early June, according to WSU, while dampwood termites swarm later in the year.
Timing helps. A winged insect indoors in spring points toward ants; one after a late-summer or autumn rain points toward termites. Neither is certain, which is why a specimen helps.
Wood damage tells a story as well. Carpenter ants leave smooth, clean galleries and coarse sawdust-like debris. Dampwood termites leave galleries that follow the grain in wet wood, and pellet-like droppings. The carpenter ants versus moisture ants guide covers the ant side.
- Pinched waist and elbowed antennae: ants
- Thick waist, straight antennae, equal wings: termites
- Spring: more often ants
- Late summer or fall after rain: more often dampwood termites
What does a termite inspection involve, and who may do it?
An inspector examines the exterior, foundation, crawl space, attic and visible wood for wood-destroying organisms and for moisture and conditions that favor them. In Washington a structural pest inspector licence covers wood-destroying organism inspections. Since 2021, SB 5317 says that licence is not valid for a complete inspection unless the inspector owns or works for a licensed inspection company.
This is information for a customer, not legal advice. In practice, ask the company for its licence number and confirm it with the state. WSU says reports should carry an inspection control number, so look for one and keep a copy.
Our guide on how to check a pest control company in Washington explains the process. For the service itself, see termite inspection.
What should a buyer or seller do about termites?
Treat the inspection as a way to learn about moisture and wood condition, not only termites. A buyer can ask for a wood-destroying organism report from a licensed structural pest inspector, read what was and was not accessible, and ask the seller about past leaks and repairs. A seller can have the same report ready.
Reports list what was found and what could not be seen. Areas blocked by storage, insulation or finished walls are noted as limits. Read those lines as closely as the findings.
If the report mentions damp wood or past activity, ask what was done and when. A repaired leak and replaced sill is a better story than an unexplained stain. Where a finding is unclear, a second opinion is reasonable, and the price of any treatment should be confirmed before you agree.
What do I do if I find dampwood termites?
Fix the moisture and remove or replace infested wood. WSU's advice is to remove form boards, keep wood off the soil, ventilate crawl spaces and not stack woodpiles against the house, and says pesticides are rarely needed. A technician maps the damaged wood and explains whether any treatment is warranted.
Replacing wood is a carpentry task. Check the contractor's registration with the Department of Labor and Industries before hiring, as Washington requires many construction contractors to register.
See dampwood termite control for how a visit is handled, and wet wood and moisture pest prevention for the moisture side.
How can I lower the chance of trouble, and when should I look?
Keep wood and soil apart, ventilate crawl spaces, fix leaks, clear gutters, store firewood off the ground and away from the house and remove stumps and old form boards. These steps are cheap, non-chemical and aimed at dampwood termites, ants and decay together. They do not guarantee against termites.
Walk the property each autumn after the first heavy rains. Look at deck posts, fence bases, the bottom of stairs and any wood that touches the ground. A screwdriver pressed into the wood tells you whether it is sound.
A look inside the crawl space once a year, in dry weather, catches wet insulation and slipped vapor barriers before they become a problem.
Typically a soft sill under a leaking window, a deck post that has rotted at the base, fascia stained below a gutter, trim that bubbles under paint, or wet insulation in the crawl space. These are the places where dampwood termites, carpenter ants and moisture ants all look first, and where an inspector spends the most time.
Older houses accumulate these spots. Additions are tied into old framing, porches are attached to walls, window frames have taken decades of rain and the crawl space may have a vapor barrier that has slipped. None of it is unusual, and most of it is fixable with ordinary repairs.
The practical message is that the moisture is the problem to solve. Treating insects without drying the wood is a short-term answer.
Early autumn is a sensible time, because WSU says dampwood termites swarm in late summer or fall and the first heavy rains show where water collects. Spring is useful for carpenter ant swarms. An inspection can be done in any season, though crawl space access is easier in dry weather.
A walk-around after the first big storm shows downspouts that overflow, ground that stays soggy and wood that never dries. Photograph what you see and note the date, which helps if you later ask an inspector to focus on a spot.
Do not wait for a swarm to look. By the time winged insects appear, a colony has usually been there for some time, and the better moment to check is before the wet season settles in.
- Soft sills and window frames
- Deck posts and stair stringers touching soil
- Stained fascia under gutters
- Wet or sagging crawl space insulation
- Old stumps, logs and form boards near the foundation
Frequently asked questions
Do I need a termite inspection to buy a house in Seattle?
Not necessarily by law. Lenders and buyers often ask for one, and it can reveal moisture and wood damage. Ask your agent or lender what is required for your purchase.
Are termites more likely in older Seattle houses?
Older houses are more likely to have damp wood, wood close to soil and past repairs, which are the conditions termites use. About half of Seattle homes were built before 1960, based on older City figures, but no figure links age to termites.
Do termite swarms mean my house is infested?
Not by themselves. A swarm shows a colony nearby. Many swarmers inside the house, especially near damp wood, is more worrying. Keep a specimen and ask for an inspection.
Is treatment always needed?
For dampwood termites, WSU says pesticides are rarely needed if infested wood is removed and moisture fixed. Subterranean termites usually call for a treatment plan, which a technician explains and prices.
How do I verify an inspector?
Ask for the company's Washington State Department of Agriculture licence number and the inspector's details, and confirm them with the state. The inspection report should carry an inspection control number.
Sources
- Washington State University PestSense – Termites fact sheet
- Washington State University – Structural Pest Management resources
- Washington State Legislature – Senate Bill Report on SB 5317 (structural pest inspector licensing)
- Washington State University PestSense – Carpenter ants fact sheet
This guide is general information for King County homeowners, not a substitute for an on-site inspection. Prices are estimates. See our disclaimer.