Subterranean Termites: Signs, Damage, Treatment and Cost

Subterranean termites are responsible for most structural termite damage in the United States. Every year, homeowners across the country lose billions of dollars to these hidden destroyers. Most homeowners insurance does not cover termite damage, which makes early identification and prompt treatment the only real protection.

There are several different types of termites, but subterranean termites are the most common and destructive. They live underground, build mud tubes to reach wood, and can stay hidden inside walls and framing for years before any visible sign appears.

This guide explains what subterranean termites look like, how to identify them, the warning signs of an active infestation, treatment costs, and the best ways to get rid of them.

Important: Subterranean termites are responsible for most structural termite damage in the United States. If you notice mud tubes, swarmers, or hollow-sounding wood, do not wait. Every month of delay can increase the cost of repair.

What Do Subterranean Termites Look Like?

Subterranean termites live in colonies divided into three main castes: swarmers, workers, and soldiers. Each caste looks different and plays a specific role.

Swarmers

Swarmers, also called alates, are flying adult termites. They have two pairs of delicate wings of equal length and functional eyes. Their color usually ranges from dark brown to black, which helps reduce water loss during the swarm. Most subterranean swarmers measure about 1/4 to 1/2 inch long with straight, beaded antennae.

Pictures of subterranean swarmers:

Workers

Workers are the most numerous caste in any colony, and they are the caste that causes wood damage. Workers have no wings, are usually 1/4 inch or smaller, and are pale white or cream-colored. They are blind and rely on chemical signals to navigate.

Pictures of termite workers:

Soldiers

Soldiers defend the colony from predators, mostly ants. They have enlarged yellow-brown heads and large black mandibles, while the rest of the body remains creamy white. Like workers, soldiers are wingless, soft-bodied, and blind.

Queens

Subterranean termite queens are dramatically larger than workers and soldiers. Their abdomen swells to produce eggs, while the legs and head remain small. Queens range from pale yellow-brown to dark brown depending on species. A mature queen can live for decades.

Signs of Subterranean Termite Infestation

Subterranean termites stay hidden almost all the time. They rarely come out into the open. Instead, they show their presence through a few recognizable signs.

1. Mud Tubes

The single most reliable sign of subterranean termite activity is the presence of mud tubes. These pencil-thick tunnels are made of soil, wood particles, and saliva. Subterranean termites build them to travel safely between the soil and their food source while staying protected from dry air and predators.

Look for mud tubes on foundation walls, concrete piers, basement walls, crawlspace framing, and around windows or doors.

2. Wood Damage

Subterranean termites consume wood from the inside out, leaving the outer surface intact. This makes the damage difficult to spot until it is severe. Tap suspect wood with a screwdriver. If it sounds hollow or feels papery, termites may have been at work.

Other warning signs include blistered or darkened wood surfaces, sagging floors, and wallpaper or paint that bubbles for no clear reason. See our guide to all signs of termite infestation for the full checklist.

3. Swarmers and Discarded Wings

If you see live winged termites inside or around your home, or piles of discarded wings near windows, doors, and light fixtures, a mature colony may be nearby. Swarming usually happens in early spring after warm rain. Our guide to flying termites explains what swarms mean and how to respond.

4. Carton Nests

If you find a carton nest in an attic, wall void, or crawlspace, there is a chance Formosan subterranean termites are involved. These nests look like compacted mud, and Formosan colonies can grow much larger than native subterranean colonies. Formosan damage spreads faster and costs more to repair.

5. Frass or Droppings

Subterranean termites use their droppings to build mud tubes, so you rarely see separate frass piles. If you find dry, pellet-like frass, it is more likely from drywood termites. See our guide to termite droppings for identification.

Subterranean Termite Damage

Of all the major termite types, subterranean termites cause the most structural damage to American homes.

Subterranean termite damage usually starts in wood that contacts the soil, such as sill plates, floor joists, framing in crawlspaces, support posts, and beams. It can later extend to trim, drywall paper, flooring, and other cellulose-based materials.

As damage spreads, floors can begin to sag, walls weaken, and small holes may appear in wood, drywall, and furniture. By the time damage is visible, repair costs can be significant. If you already see visible damage, see our guide on termite damage repair for repair costs and DIY-friendly options.

What Do Subterranean Termites Eat?

Subterranean termites feed primarily on wood and other materials that contain cellulose. Beyond structural lumber, they may also consume:

• paper, cardboard, and books;
• wallpaper and paint with paper backing;
• cotton and other plant-based fabrics;
• dead plant material in soil.

They can also damage non-food materials such as pipe insulation, pool liners, and rubber gaskets while searching for moisture or a path to wood. This is why even concrete-and-steel buildings can suffer subterranean termite damage if workers reach wooden interior framing.

Where Do Subterranean Termites Live?

In the Ground

Subterranean termites live underground, where soil provides the moisture they need. Colonies are often found below the surface near tree stumps, buried wood, or wood-to-soil contact points. Cracks in foundations, slabs, or hollow concrete blocks can give them access to a structure.

In Houses

Inside homes, subterranean termites move through cracks in concrete, expansion joints, hollow block foundations, plumbing penetrations, crawlspaces, and wall voids. Once inside, they remain hidden behind drywall, under flooring, and inside framing, often for years before discovery.

In the United States

Subterranean termites occur in most US states. Activity is highest in warm, humid states such as Florida, Texas, North Carolina, South Carolina, Georgia, Alabama, Louisiana, Mississippi, Tennessee, Virginia, Hawaii, and California. Even in colder states, infestations can occur in heated structures.

Habits of Subterranean Termites

Colony Size

Native subterranean colonies can contain tens of thousands to hundreds of thousands of termites. Healthy mature colonies can grow much larger. Formosan subterranean colonies can be especially large and destructive.

Aggressiveness

Subterranean termites are highly destructive because they work continuously and stay hidden. Most homeowners insurance does not cover termite damage, so repair costs usually fall on the homeowner.

Adaptability

Because subterranean termites depend on stable moisture and access to wood, they thrive around modern homes. Crawlspaces, leaking pipes, mulch beds, decks, fences, and wood siding can all create conditions they need.

How Do Subterranean Termites Get Into a House?

Subterranean termites use several common entry points:

• Mud tubes from soil up to wood framing;
• cracks in the foundation, slab, or basement walls;
• hollow concrete blocks or gaps with no termite shield;
• wood-to-soil contact, including porches, deck supports, fence posts, and sill plates touching the ground.

Excess moisture is the single biggest risk factor. Leaking pipes, clogged gutters, dripping AC units, and poor drainage create the wet conditions termites need. Wood that touches damp soil is especially vulnerable.

How to Get Rid of Subterranean Termites

Treatment depends on how widespread the infestation is. Use this approach as a starting point.

1. Treat the Soil Around the Foundation

For subterranean termites entering from soil, a proper perimeter soil treatment can create a treated zone around the foundation. This is one of the strongest options when the soil is accessible and the product is legal for homeowner use in your state.

See our guide to Termidor SC vs Taurus SC for soil treatment.

2. Install Bait Stations Around the Structure

For subterranean termites, bait stations are a practical long-term DIY option. Stations placed around the perimeter can detect termite activity and help suppress or eliminate colony pressure over time.

See our guide to the best termite bait stations for home protection.

3. Use Spot Treatment for Active Areas

For live termites visible in wall voids, around baseboards, or in exposed wood, foam termiticides can help with localized activity. Foam expands into galleries and reaches places a surface spray may miss.

See our guide to the best termite sprays for spot treatment.

4. Treat Exposed Wood

For unfinished wood, framing, joists, attic beams, crawlspace lumber, or repair areas, apply a borate wood treatment. Borate can help protect exposed wood during repairs, remodeling, or construction.

5. Consider Professional Treatment for Severe Cases

For widespread, recurring, or hidden infestations, especially when structural damage is suspected, professional treatment is the safer call. A professional inspection can identify the species, locate active galleries, and recommend whether bait stations, liquid soil treatment, drilling, or another method is appropriate.

Subterranean Termite Treatment Cost

Treatment cost depends on the method, size of the home, accessibility, location, and how widespread the infestation is.

DIY treatment costs:

• borate wood treatment: about $40-100;
• foam spot treatment kit: about $25-60;
• bait station system: about $80-300;
• DIY perimeter setup: often $200-500+ depending on product and home size.

Professional treatment costs:

• initial termite inspection: often free to $150;
• liquid soil treatment: often $1,500-3,500;
• professional bait station installation: often $1,200-2,500+ with annual service;
• spot treatment by a professional: often $250-1,000;
• damage repair: can range from minor repairs to $20,000+ in severe cases.

The final price usually depends on the treatment method, colony severity, structure type, local labor costs, and the pest control company you choose.

For a broader overview of inspection and treatment options, see our termite inspection cost guide.

Tips for Subterranean Termite Control

Eliminate Moisture

Subterranean termites need moisture to survive. Repair leaking pipes, dripping faucets, and clogged gutters. Direct downspouts away from the foundation. Make sure crawlspaces, basements, and attics ventilate properly.

Remove Termite Food Sources

1. Remove tree stumps, scrap wood, and lumber piles near the house.
2. Store firewood elevated and away from the foundation.
3. Replace mulch touching the foundation with gravel or stone where practical.
4. Inspect wooden fences, decks, and posts annually for hidden damage.
5. Seal foundation cracks and screen outdoor vents.

Install Termite Bait Stations

Homeowners use bait stations to monitor and control subterranean termites around the structure. For best results, place stations around the perimeter and inspect them on a regular schedule.

Protect Vulnerable Wood

Pretreating exposed framing, supports, wall interiors, and other unfinished wood with a borate solution can add long-lasting protection, especially during construction or major repairs.

Schedule Annual Inspections

Annual termite inspections can catch activity early, before the repair bill grows. Many pest control companies offer free inspections as part of their sales process.

Interesting Facts About Subterranean Termites

1. Subterranean termites are among the hardest termite species to detect early because they stay hidden inside soil, walls, and wood.
2. They need stable moisture to survive, which is why they build mud tubes between the colony and food sources.
3. Formosan subterranean termites are sometimes called “super termites” because their colonies can become very large and destructive.
4. Subterranean termites cause billions of dollars in damage to US homes every year.
5. A mature subterranean queen can live for decades under the right conditions.

Subterranean vs Drywood Termites

For a full breakdown, see our guide to drywood termites.

Subterranean vs Dampwood Termites

Frequently Asked Questions

How fast do subterranean termites cause damage?

Significant structural damage usually takes time, but the pace depends on colony size, termite species, moisture, and the structure. Formosan subterranean colonies can cause damage faster than native subterranean colonies because they can grow much larger.

Can I treat subterranean termites myself?

For early-stage or limited infestations, DIY may be realistic with bait stations, soil treatment, and foam treatments. For widespread infestations, structural damage, or recurring activity after DIY treatment, professional service is the safer choice.

Are subterranean termites dangerous to humans?

Subterranean termites do not bite, sting, or transmit disease. The danger is structural. They damage homes, weaken floors and walls, and can create expensive repair problems if left untreated.

How do I know if I have subterranean or drywood termites?

Subterranean termites build mud tubes and require soil contact. Drywood termites do not build mud tubes and often leave dry, pellet-like droppings. Mud tubes usually point to subterranean termites; dry pellets and kick-out holes often point to drywood termites.

Will bleach kill subterranean termites?

Bleach can kill termites on contact, but it has no colony control or transfer effect. It cannot reach the colony or queen. For real control, use termite products designed for the situation, such as bait stations, soil treatment, or foam spot treatment.

How much does a termite inspection cost?

Independent termite inspections often cost around $75-150, though many pest control companies offer free inspections as part of their sales process. Home buyer WDI reports may cost more depending on location and requirements.

Does homeowners insurance cover subterranean termite damage?

Usually no. Homeowners insurance generally treats termite damage as a preventable maintenance issue, so it rarely covers treatment or repair costs.

How long does subterranean termite treatment last?

Liquid soil treatments can provide years of protection when applied correctly. Bait station systems require ongoing inspection and maintenance. Borate wood treatments can last a long time when applied to accessible unfinished wood.

Conclusion

Subterranean termites are among the most destructive wood-destroying pests a homeowner can face. Because they stay hidden in soil, wood, and walls, they often cause serious damage before the problem becomes visible.

The right approach is simple: recognize warning signs early and match the treatment to the situation.

• Mud tubes around the foundation → bait stations or soil treatment
• Visible live termites indoors → foam spot treatment
• Unfinished or exposed wood → borate treatment
• Severe or recurring infestations → get termite inspection quotes from local pros

The earlier you act, the cheaper and easier the solution is likely to be. Annual inspections are one of the most effective tools against subterranean termites.

Related Reading

• Termite Mud Tubes: What They Look Like and What to Do
• Best Termite Killer for Soil: Termidor SC vs Taurus SC
• Termiticides for Termite Control
• Best Termite Sprays for Spot Treatment
• Best Borate Wood Treatment for Termites
• Termite Droppings: What Frass Looks Like
• Best Pest Control Services Compared