If you’ve spotted what looks like a termite nest or mud tubes on a brick wall, you’re almost certainly looking at subterranean termites using the masonry as a highway to reach the wood inside your home. Termites don’t eat brick. They build pencil-width mud tubes over it to stay protected and moist while traveling between their underground colony and the timber framing behind your walls. The nest itself is underground, and what you see on the brick surface is just the visible tip of a much larger problem.
What You’re Actually Seeing
The structures on your brick wall are shelter tubes, not the nest itself. Termites build these from soil, saliva, and waste to create a sealed tunnel that holds in moisture as workers travel from the ground up to their food source. The tubes are typically about the diameter of a pencil, though heavily trafficked routes can be thicker. They usually run vertically up the foundation or along mortar joints, and sometimes branch out across the wall surface.
Over 90% of a termite colony sits underground. The mud tubes on your wall are a transit system, not a home. If you see them, an active colony with potentially hundreds of thousands of termites is already established in the soil nearby, and workers may already be feeding on the wooden structure behind the brick veneer.
How Termites Get Through Brick Walls
Brick itself is impenetrable to termites, but brick walls are full of entry points. Termites can squeeze through gaps narrower than 1/32 of an inch, which means hairline cracks in mortar, expansion joints, and plumbing penetrations are all viable doorways. Once through, they travel behind the brick veneer where you’ll never see them, feeding on the wooden framing that gives the house its structural integrity.
Weep holes are one of the most common entry points. These small openings near the base of brick walls are designed to let moisture drain out, but they also create a direct path for termites to enter. Weep holes positioned lower than 75 millimeters (about 3 inches) from the ground are particularly vulnerable. Blocked or poorly maintained weep holes trap moisture inside the wall cavity, and that dampness creates exactly the conditions termites thrive in.
Why You Shouldn’t Scrape Off the Mud Tubes
The instinct to knock the tubes off your wall is understandable but counterproductive. Removing the tubes removes a warning sign, not the termites. The colony simply reroutes, often behind plaster or deeper inside the wall cavity where you can’t see the activity at all. Meanwhile, you’ve convinced yourself the problem is solved.
Intact tubes also serve as a diagnostic map for pest professionals. They show exactly where the colony is crossing into the structure and how active the route is. Smearing or scraping them away destroys that evidence, which can make treatment planning harder and less precise. If you want to check whether the infestation is currently active, break open a small section of one tube and look for small, creamy-white worker termites inside. Then leave the rest untouched until a professional inspects.
Can Termites Damage the Brick Itself?
No. Termites cannot consume or structurally weaken brick, concrete, or mortar. The damage happens to the wood behind the masonry. Because brick homes still rely on timber framing for their core structure (wall studs, floor joists, sill plates, roof trusses), termites can cause serious structural damage without ever leaving a mark on the exterior brick. This is what makes brick-veneer homes deceptive: the outside looks fine while the wooden skeleton inside is being hollowed out.
Treatment Options
Professional treatment falls into two categories: liquid soil barriers and baiting systems. Most infestations on brick walls are handled with one or a combination of both.
Liquid Soil Barriers
A technician injects a liquid termiticide into the ground along the foundation, beneath concrete slabs, and within foundation walls. A typical treatment can involve hundreds of gallons of product. Modern formulations are non-repellent, meaning termites don’t detect the treated soil and tunnel through it, picking up the chemical and dying. This approach also cuts off the colony’s access to supplemental moisture from the soil, so termites already inside the structure die off as well. Liquid barriers tend to work faster than baits and are generally more reliable at resolving infestations on the first attempt.
Baiting Systems
Bait stations are installed in the ground around the property, containing cellulose food laced with a slow-acting compound. When termites find the bait, they carry it back to the colony, where it spreads through the population. Workers die when they attempt to molt after ingesting it. The limitation is speed: weeks or months may pass before termites discover the bait stations underground, and the elimination process can take several months or longer to complete. Some feeding and damage may continue during that window. Bait stations are sometimes installed indoors directly over active mud tubes for more targeted results.
Many pest control companies offer perimeter applications, treating the entire exterior foundation with a liquid product and spot-treating any infested or high-risk areas inside. This is often the most practical approach for brick homes where termite activity is visible on the wall surface.
Preventing Termites on Brick Walls
The most effective long-term prevention targets the entry points termites exploit. Start with weep holes: install grated covers or mesh screens with an aperture size of 1/55th of an inch or smaller, which is fine enough to block subterranean termites (responsible for about 95% of termite damage). Never seal, paint, or caulk weep holes shut. They need to stay open to drain moisture, and trapped moisture inside the wall only makes the problem worse.
Keep plants at least 18 inches away from weep holes and clear any debris or soil that has built up around them. Mulch, garden beds, and stored wood against the wall all create moist, sheltered conditions that give termites a launching point. Ensuring the soil grade slopes away from the foundation helps reduce moisture buildup along the base of the wall, making the area less attractive to colonies looking for a way in.
If your home has had a liquid soil treatment in the past, these barriers do degrade over time. Regular inspections, typically annual, catch new activity before it reaches the structural timber. Catching mud tubes early on the exterior of a brick wall is actually a best-case scenario. It means the termites showed themselves before disappearing entirely behind the veneer.