How Do Termites Get Into the House? The Entry Points You Can't See

Once the initial "why me" question settles down, a very practical one takes over: by what route, exactly? Not why they picked this house — that's a separate conversation — but the physical mechanics of how the insects moved from wherever they came from to inside your walls. And once you understand the routes, you can start closing them off.

The straight answer to how do termites get in the house comes down to two very different routes and one thing they have in common. Subterranean termites come up from the ground, through the soil, into your foundation. Drywood termites come in through the air, on wing, landing on wood they can access. And both of them exploit the same thing to make it happen: gaps so small you'd never think about them — sometimes as narrow as 1/32 of an inch.

Let's walk through each route in enough detail to actually be useful, cover the gaps you'd never suspect, and separate what you can seal yourself from what needs a treated barrier.

Quick Answer: How Termites Get In

Subterranean termites: Up from the soil, through foundation cracks and slab penetrations, often traveling inside protective mud tubes.

Drywood termites: In through the air as winged swarmers landing on accessible unpainted wood — eaves, vents, window frames.

The gaps that matter: Cracks as small as 1/32", utility penetrations, expansion joints, weep holes, unscreened attic vents.

Can I seal them all myself? Some — the visible gaps. But subterranean entry through slab and foundation typically needs a professional barrier.

How do I find where mine are getting in? A thermal inspection maps actual entry, not just theoretical points. Call Termike at (888) 683-3592.

Why You Can Trust Termike Pest Control

License: California Structural Pest Control Board — License PR8832 (Branch 2 & 3 certified)

Membership: National Pest Management Association (NPMA)

Experience: 20+ years serving Orange County, LA County, Riverside & San Bernardino County

Entry-Point Mapping: FLIR thermal imaging identifies where termites are actually coming in — the gap between "sealed the visible ones" and "closed the real ones"

Barrier + Seal Strategy: We combine entry-point sealing with soil treatment for the gaps you can't

Route 1: Subterranean — Up From the Ground

When people ask how do termites get in the house and they're dealing with the more common of the two species, the answer starts underground. Subterranean colonies live in the soil, sometimes tens of feet away from your home, and the workers forage outward looking for wood. When their tunnels intersect your foundation, they find any opening between soil and structural lumber and follow it up.

Common subterranean entry paths:

•       Foundation cracks. Even hairline cracks in concrete let termites pass through. Older poured foundations and slab-on-grade construction both develop these over decades

•       Slab penetrations. Every place a pipe, cable, or drain passes through the concrete is a potential entry point unless properly sealed

•       Expansion joints. The gaps between concrete sections — driveways meeting foundations, garage slabs, patios — are direct paths

•       Cinder-block voids. Hollow-core block foundations offer internal channels termites can travel up unseen

•       Direct wood contact. Anywhere structural wood touches soil — a rotted sill plate, a wood step, a fence post against the house — is a bypass they don't need cracks for

The telltale sign of this route is the mud tube — a pencil-thin, dirt-colored tunnel termites construct on foundation walls and support piers to travel safely between soil and wood. If you see them, you're looking at active subterranean entry. Termike's guide on what to do if you find mud tubes on your foundation covers exactly what those mean and the next steps. The UC Integrated Pest Management Program details how subterranean termites approach and enter structures from soil-based colonies.

Route 2: Drywood — In Through the Air

The other route is completely different. Drywood termites don't come from soil at all — so how do termites get in the house when they're drywoods? Mature colonies produce winged reproductives called swarmers that fly out (usually on warm days, often after rain), land on wood, shed their wings, and start a new colony wherever they can burrow in. Which means for drywoods, "how did they get in" is answered by "they flew here and found a soft spot."

Common drywood landing and entry spots:

•       Attic vents. Unscreened or torn-screen gable and eave vents are among the most reliable drywood entry points into Southern California homes

•       Eaves and fascia boards. Exposed, unpainted, or weathered wood at the roofline is prime landing habitat

•       Window and door frames. Gaps around window casings, especially where paint has failed and wood has weathered

•       Untreated wood siding and trim. Any bare wood surface a swarmer can land on and start chewing into

•       Roof line penetrations. Vent stacks, chimney flashing, and any place caulking has failed

The U.S. Environmental Protection Agency notes that drywood termites are especially challenging because they don't need soil contact — a single swarming pair reaching accessible wood is enough to establish a colony. That's why the roof line and attic on Southern California homes deserve as much attention as the foundation.

The Gaps You'd Never Suspect

Here's the part that catches people off guard: the openings that matter for how do termites get in the house are much smaller than the ones people mentally check for. A workman's idea of "well sealed" and a termite's idea are different.

•       1/32-inch cracks. That's roughly the width of a business card edge. A subterranean worker can pass through it

•       Utility penetrations. Where cables, gas lines, water lines, and conduit enter the structure — the small gap between pipe and drywall or foundation is often unsealed

•       Weep holes. The small gaps at the bottom of brick veneer that let moisture escape can also let termites enter unless properly screened

•       HVAC penetrations. Where refrigerant lines cross the exterior wall, or condensate drains exit — small, often unsealed

•       Garage slab-to-wall joint. The gap where the garage floor meets the wall is a very common bypass

•       Foundation vent screens. Damaged or missing crawlspace vent screens invite both subterranean and drywood entry

Any single one of these might look trivial. Collectively, they're how nearly every infestation actually starts. A useful mindset shift: if a fine-tipped screwdriver could slip through it, so could a termite.

What You Can Seal — and What You Can't

Now the practical division of how do termites get in the house, in DIY terms. Some of these entry points are genuinely accessible territory. Others aren't, and pretending otherwise costs you time.

Homeowner-Sealable

1.     Attic and crawlspace vent screens. Replace or repair torn screens with fine mesh

2.     Utility and HVAC penetrations. Caulk or use expanding foam at visible penetrations

3.     Visible foundation cracks. Hairline cracks can be sealed with an appropriate concrete crack sealer

4.     Weep hole screens. Purpose-made stainless weep hole covers keep pests out while preserving drainage

5.     Failed paint and caulking. Re-paint exposed exterior wood; re-caulk gaps around window and door frames

Needs a Professional Approach

6.     Subterranean entry beneath the slab. You can't seal what you can't see. A soil treatment establishes a treated zone at the perimeter that colonies can't cross — Termike's foundation termite treatment covers how this is done

7.     Cinder-block void entry. Requires a targeted approach into the block cavities that's beyond DIY tooling

8.     Established drywood colonies. Once a colony is inside, sealing the entry doesn't remove it — treatment does

9.     Identifying where they're actually coming in. The most common mistake in DIY entry-point sealing is closing gaps that weren't being used while leaving the actual route open. Thermal inspection maps real activity

The Species Matters for the Solution

One more piece of context, because how do termites get in the house also tells you the treatment. If mud tubes on the foundation are the tell, you're dealing with subterranean entry and the solution centers on the perimeter — soil treatment, sealing at the slab, and correcting wood-to-soil contact. If frass piles under the eaves or attic activity are the tell, you're dealing with drywood entry and the solution centers on the wood itself — spot treatment, whole-structure fumigation for widespread cases, and hardening the roof-line gaps. The subterranean termites and drywood termites overviews explain the differences in more detail.

The Bottom Line

How do termites get in the house comes down to two routes and a handful of very small gaps: subterranean up from the soil through foundation cracks and slab penetrations, drywood in through the air landing on unpainted wood at the roof line, and both exploiting the openings people don't think twice about. You can seal a real portion of the DIY-accessible ones yourself. The rest — the sub-slab paths, the block-void routes, and the actual identification of which entries are in use — call for professional eyes and tools. Knowing the routes is step one; closing them is what actually keeps them out.

Frequently Asked Questions About How Do Termites Get In The House

Q: How do termites physically get into a house?

A: Two very different routes, depending on species. Subterranean termites come up from the soil, entering through foundation cracks, slab penetrations, expansion joints, cinder-block voids, or direct wood-to-soil contact — usually building protective mud tubes to travel safely. Drywood termites come in through the air as winged swarmers that land on accessible unpainted wood at the roof line, eaves, window frames, or attic vents and burrow in to start new colonies. Both exploit gaps as small as 1/32 of an inch.

Q: Can termites come up through a concrete slab?

A: Yes, and this is one of the most misunderstood entry paths. Termites don't chew through solid concrete, but they don't need to — they use the cracks, expansion joints, and small openings around plumbing and utility penetrations that every slab has. Even a hairline crack in a modern slab is enough for subterranean workers to pass through. Because the entry is beneath the finished floor and hidden, sub-slab entry typically calls for a professional soil treatment rather than something you can seal from above.

Q: What are the actual entry points I should seal at my home?

A: Focus on the DIY-accessible ones first: repair or replace torn attic and crawlspace vent screens; caulk or foam visible utility and HVAC penetrations where cables, pipes, and refrigerant lines cross the exterior; seal hairline foundation cracks with appropriate concrete crack sealer; install purpose-made stainless weep hole covers on brick veneer; and re-paint and re-caulk exposed exterior wood, especially at eaves, window frames, and door frames. Sub-slab entry, cinder-block voids, and unknown routes need professional identification.

Q: How do I find where termites are actually getting in?

A: This is the most common mistake in DIY entry-point sealing — closing gaps that weren't being used while leaving the actual route open. Surface signs (mud tubes on the foundation, frass under the eaves) tell you which route is in use, but they don't pinpoint the entry gap. Thermal imaging maps active termite locations through walls and finishes, which is how a professional inspection identifies real entry rather than theoretical points. Termike can inspect and map that — call (888) 683-3592.

Want to Know Where Yours Are Getting In? Free Inspection

The gaps you can seal yourself matter — but so do the ones you can't see. Termike's free FLIR inspection maps the actual entry routes at your specific home and tells you exactly what needs sealing and what needs a treated barrier.

Call: (888) 683-3592

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