Western subterranean termites in San Francisco buildings: how a technician finds the soil link and treats the structure.
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Subterranean termites live in soil and reach a building through mud tubes, cracks and wood that touches the ground. UC IPM says the western subterranean termite swarms on calm sunny days right after the first autumn rains, especially around the Bay Area. San Francisco Pest Control connects San Francisco callers with a technician who confirms the price first.
Most people meet subterranean termites in one of two ways. Either a cloud of winged insects appears at a window on a still, bright day just after the first real rain of autumn, or a handyman pushes a screwdriver into a sill and the wood gives way like wet cardboard. Both are the same animal telling you the same thing: a colony is working somewhere nearby, and it is probably connected to the ground.
UC IPM describes the western subterranean termite as a species that swarms in calm, sunny periods right after the first autumn rains, a pattern it calls especially pronounced in the San Francisco Bay Area. This page explains how a technician finds the link between soil and structure, the ways it can be treated, and what shapes a quote. San Francisco Pest Control is a call line that connects you with an independent local pest-control company; phones are answered 24/7, and a same-day visit is offered only when a technician is free.
Do not spray a mud tube, drill into suspect framing or pull off damaged wood yourself. You can disturb the evidence a technician needs and release dust or chemicals into your living space. Keep children and pets away from any area a technician treats until it is explained.
A technician checks the foundation perimeter, the crawl space if there is one, porch and stair framing, and any wood buried in planters or soil. Mud tubes and damaged timber show where the colony is reaching in.
Suspect wood is tapped and probed to see how far it goes. The technician notes which areas are active, which look old, and which need a closer look from a carpenter.
The choices usually come down to a liquid soil treatment, a bait system, or a mix. The technician explains why one fits your building and what access it needs before you decide.
Treatment goes along the foundation and at the points where termites cross from soil to wood. On a building with a raised floor, that can mean working from the crawl space as well as the outside.
You get a list of what invites termites back: wood in contact with soil, planters against walls, blocked sub-floor vents and damp crawl-space ground. Some of it is yours to change, and some needs a contractor.
Ask what the visit includes, whether a re-check is offered, and what a report would say if the property is sold. The answer is agreed before any work begins.
No San Francisco price for subterranean termite work was confirmed in sources, so no dollar figure is printed. These are the things that move a quote.
| Job | Typical range | What it includes |
|---|---|---|
| Footprint and perimeter of the building | Scales with the property | A long row house and a detached cottage have very different lengths of foundation to treat |
| Method chosen | Set after inspection | Soil treatment, bait stations and a combination are priced differently and need different visits |
| Access to the soil | Varies by site | Concrete, decks and shared walls can mean drilling or extra labour |
| Crawl space or basement work | Set on inspection | Low clearance and wet ground take longer to work through |
| Follow-up checks | Agreed up front | Ask which visits are included and which are charged separately |
These are cost drivers, not prices. A technician confirms the price with you on site before any treatment begins.
UC IPM says western subterranean termites swarm in calm, sunny periods right after the first autumn rains, and that this is especially pronounced in the San Francisco Bay Area. A swarm shows that a mature colony exists nearby. It does not show how large it is or whether it is in your building.
Swarmers are the winged reproductive termites. They leave the colony to pair up and start new ones, then shed their wings. A pile of wings on a sill is often the first thing people find, because the insects themselves last only a short time.
We give no date for this, since the first rain moves from year to year. The useful habit is to watch for it after the first wet, still, bright day and to keep any wings you find in a sealed bag or a sheet of tape so a technician can identify them. For more on the pattern, see our guide to termite swarms after the first rain.
Subterranean termites need contact with soil or another moisture source and travel in mud tubes. Drywood termites live entirely inside dry wood and push out small, hard pellets. The two are treated differently, so a technician identifies which one it is before recommending anything.
Evidence is the main clue. Mud tubes and damp, layered damage near the ground point to subterranean termites. Tiny six-sided pellets under a beam or on a window sill point to drywood termites, which are covered on our drywood termite control page.
A building can hold more than one kind, and wood damage can also come from fungus rather than insects. If you are not sure, a termite inspection is the way to get a clear answer in writing.
No. Winged termites have a thick, straight waist, straight antennae and two pairs of wings of equal length. Winged ants have a pinched waist, bent antennae and front wings longer than the back ones. A clear photo helps a technician tell them apart.
The mistake runs both ways. Some people ignore swarming termites because they assume they are ants, and others panic over harmless ant fliers. Catching a few insects in a jar or on sticky tape and looking closely at the waist and wings settles most cases.
If the insects are ants, our ant control page covers what a technician does about them.
Keep evidence, do not disturb it, and write down where you saw it. Spraying a store-bought product into a mud tube or a damaged board can push termites away from the spot a technician needs to find and make the colony harder to trace.
Photograph mud tubes, wings and damaged wood with something for scale, such as a coin. Note the date and the weather, because a swarm after rain is a clue in itself.
Move stored boxes away from foundation walls and crawl-space access so the technician can reach them. Do not pull off damaged wood, which can hide the edge of the activity.
A termiticide is applied in the soil along the foundation, sometimes by trenching or drilling through hard surfaces, so that termites travelling between ground and wood meet a treated zone. It suits many buildings but needs access to the soil, which can be limited where a house sits against its neighbours or a patio covers the edge.
Stations are placed in the ground around the building and checked on a schedule. Foraging workers feed on the bait and carry it to the colony. It involves more visits over time and less disturbance to landscaping, and the technician should explain how the stations are monitored.
Where damage is limited to a single sill, post or section of framing, treatment can be aimed at that wood together with a repair of the moisture or soil contact that fed it. A technician has to be confident that no other colony points are active before this is enough.
San Francisco has dry summers and wet winters, with sea fog that keeps many exterior surfaces and crawl-space soils damp for long stretches. Termites need moisture, and a building whose foundation, planters and downspouts all drain toward the wall gives them some. A technician often learns as much from the drainage around the house as from the wood.
Roughly 45 percent of San Francisco homes were built in 1939 or earlier, according to census-based estimates, and the median home dates from 1948. Older buildings often have raised floors, timber piers and original wood sills close to the soil. Those are the places subterranean termites reach first, and also the places that are hardest to see without a flashlight and a ladder.
Attached houses and flats share walls and sometimes foundations. A colony does not stop at a property line, so a technician may ask whether neighbours have seen swarms or damage, and an owner of one unit may need to coordinate with the building's other owners before treatment is practical.
Hillside lots bring their own habit: soil movement and runoff can expose or bury sill plates over the years. If wood that was once above the ground now sits in it, mention that when you call.
If it's an emergency, call now. For non-urgent subterranean termite control, send the form and we'll call you back.
Not sure if you're covered? Check your ZIP code.
Termite inspection for San Francisco houses and flats: swarms, sales reports and what a technician looks at.
Drywood termites in San Francisco attics, trim and roof framing: how they are found and the options for treating them.
Dry rot and other wood damage in San Francisco homes: telling fungus from termites, finding the moisture and what comes next.
According to UC IPM, western subterranean termites swarm in calm, sunny periods right after the first autumn rains, and the effect is especially pronounced in the San Francisco Bay Area.
A Wood Destroying Pests and Organisms report is the written findings of a California Branch 3 inspection: termites, wood-boring beetles, dry rot and fungus.
Dry rot is a wood-decay fungus, not an insect, and it needs moisture to grow despite the name.
Termites are a known concern in the Bay Area, and UC IPM notes that western subterranean termites swarm there after the first autumn rains. We cannot say how many buildings are affected. An inspection is the only way to know about yours.
Many subterranean termite treatments are done from the outside and the crawl space, so staying in the home is often possible. The technician tells you what is planned and whether any room needs to be empty before work begins.
Products sold to homeowners can kill termites they touch, but they rarely reach a colony in the ground or hidden in framing. The treatment has to meet the path between soil and wood, which is why a technician maps the building first.
Ask the technician what signs to watch for, and about re-checks. New mud tubes, fresh swarmers or soft wood in the same place are reasons to call again. Be wary of anyone who promises an outcome before looking.
California real-estate sales often rely on a Wood Destroying Pests and Organisms Inspection Report. Ask your agent what is required and see our termite inspection page for how the inspection works.
San Francisco Pest Control is a call line that connects you with an independent local pest-control company. Phones are answered 24/7, and a same-day visit is offered only when a technician is free. Call (855) 974-4733 to describe what you have found.