How Formosan Termites Get Into Homes and Buildings

Formosan termites get into buildings in two main ways: from the soil, through cracks, expansion joints and utility openings in the slab, and from the air, when swarming termites land on a damp spot in the structure and start a colony there. Once inside, they hide in wall voids and build nests out of sight, which is why most owners only find them after the damage is done.

Knowing these entry routes tells you where to look and what to fix. This guide walks through each pathway, explains why South Florida buildings are so exposed and shows what actually keeps Formosan termites out. If you are new to this species, start with our overview of what Formosan termites are.

Why Formosan Termites Are So Good at Getting In

The Formosan subterranean termite (Coptotermes formosanus) is built for invasion. UF/IFAS describes underground colonies of several million termites, with workers that forage up to about 100 meters (roughly 330 feet) in the field. A colony that big, searching that far, tests every weak point in a foundation.

Three habits make it an especially effective intruder:

• It is persistent with small openings. UF entomologists note that Formosan termites find small cracks in concrete, enlarge them and use them as foraging routes. The idea that they bore through solid concrete is a myth; they do not need to.
• It builds its own climate. Workers travel inside mud tubes and fill hollow spaces with carton nest, a mix of soil, chewed wood, saliva and feces that holds moisture.
• It does not need the ground. If a building supplies water, a colony can live entirely above the soil.

South Florida concentrates the risk. Broward and Miami-Dade were the first counties where the Formosan and the Asian subterranean termite were documented established together, according to UF/IFAS (a 2026 University of Florida study has since found the Asian species as far north as Brevard and Hillsborough counties), and in 2016 UF researchers projected that half the structures in South Florida could be at risk of subterranean termite infestation by 2040. For the bigger picture, read why Formosan termites are so concerning.

Entry Route 1: Up From the Soil Through Mud Tubes

Most Formosan infestations start in the ground. Workers leave the underground colony and build mud tubes, about a quarter to half an inch wide, up the foundation to reach wood. The tubes keep them in the dark and protect them from drying out and from predators such as ants.

Common ground-level entry points include:

• Wood touching soil. UF entomologists put it plainly: any wood-to-ground contact is an inviting entrance. Think door frames, porch steps, deck posts, fence boards attached to the house and wooden planters against a wall.
• Siding, stucco or foam board that runs below grade. Termites can tunnel behind them where nobody sees the tubes.
• Soil, mulch or plants piled against the wall, which hide tubes and keep the soil moist.

Entry Route 2: Slab Cracks, Expansion Joints and Utility Penetrations

Most South Florida homes sit on concrete slabs, and many owners assume a slab blocks termites. It does not. UF/IFAS Featured Creatures notes that Formosan termites commonly enter through expansion joints, cracks and utility conduits in slabs. Those openings lead straight to bottom plates, door jambs, cabinets and the wood inside walls.

The weak points in a slab are predictable:

• Expansion and control joints where two pours meet, such as between the house slab and a garage, porch or addition
• Plumbing and electrical penetrations, the gaps around pipes, drains and conduits that pass through the slab, often hidden behind tubs, sinks and toilets
• Settlement and shrinkage cracks, which widen as the slab ages
• The joint between slab and block wall, especially behind baseboards

This is why garages, bathrooms and kitchens are frequent hot spots. Our article on why garages often show termite problems first explains how the garage slab joint becomes an entry route.

Entry Route 3: Swarmers Drawn to Your Lights

Every spring, mature Formosan colonies release winged reproductives called alates. In Florida, Formosan termites swarm between early April and late June, shortly after sunset, with peak activity in May, according to UF/IFAS. A single swarm can contain tens of thousands of termites.

Alates are strongly attracted to light, which draws them to porch lights, lit windows and even boats. They slip in through open doors, unscreened windows, vents and gaps around screens. After the flight, they drop their wings, pair off and look for a crack or crevice with enough moisture to start a colony.

Most swarmers that land inside a dry home die quickly. The danger comes when a pair finds wood and water in the same spot, which leads to the next route. If you are unsure what flew in, compare it with our guide to termites vs. flying ants.

Entry Route 4: Aerial Colonies in Wet Spots Above the Ground

An aerial colony is one that lives inside a building with no connection to the soil. UF/IFAS Featured Creatures explains that a pair of alates that finds food and moisture in a building can start a colony with no ground connection, and that more than 25% of the infestations found in urban southeastern Florida in one survey were caused by aerial colonies.

The moisture usually comes from the building itself:

• Leaky plumbing in walls, under sinks and around water heaters
• Air conditioning condensate from drain lines, pans and air handlers
• Flat roofs that pool rainwater, which UF researchers single out on high-rise buildings
• Roof and window leaks, especially after storms
• Planter boxes and balconies that keep wood or wall cavities damp

This route explains why condo towers, apartment buildings and upper floors can have Formosan termites. It also explains why an aerial infestation can survive a soil treatment around the foundation: the colony never touches the treated soil.

Entry Route 5: Infested Wood and Materials You Bring In

People also spread Formosan termites. UF/IFAS links their expansion to the termites’ own flights and to people moving infested material. Not every wooden item is a real risk, though. UF/IFAS research on mulch found that termites survive poorly once chipped and separated from their colony, so bagged mulch is an unlikely source. The bigger concern is larger pieces of infested wood, such as railroad ties or salvaged timbers, that can carry enough termites to keep reproducing.

Practical rules:

• Inspect used lumber, old beams and wooden landscape pieces before you bring them onto the property.
• Do not stack lumber, firewood or wood debris against the house. The EPA advises against storing firewood or wood debris next to the home.
• Have trees near the house checked. Formosan termites hollow out living trees and fill them with carton nest, which weakens trees and can bring a colony close to the roofline.

How to Block Formosan Termite Entry Points

You cannot seal a building tightly enough to stop a colony of millions on your own, but you can remove the conditions that make entry easy and make activity easier to spot.

Remove Moisture

• Fix plumbing leaks, roof leaks and dripping AC lines quickly.
• Make sure condensate lines drain away from the foundation.
• Keep flat roofs, gutters and balcony drains clear so water does not stand.

Break Wood-to-Soil Contact and Keep the Foundation Visible

• Keep wood off the soil; use concrete or metal supports where possible.
• Keep mulch thin and leave a visible strip at the foundation, so mud tubes stand out. Our guide to how landscaping choices attract termites covers mulch, irrigation and plantings in detail.
• Seal cracks in the foundation and gaps where utilities pass through walls, as the EPA recommends.

Watch at Swarm Time

• Switch off unneeded outdoor lights after sunset from April through June.
• Keep window and door screens in good repair.
• Check windowsills and light fixtures for wings in the morning.

For a full prevention plan, see how to prevent Formosan termite infestations.

How Professionals Stop Formosan Termites

UF/IFAS states that control of Formosan subterranean termites requires professional pest control services and that over-the-counter products are unlikely to be effective. Professionals use two main tools:

• Bait systems. Stations in the soil around the structure hold a slow-acting bait that workers share with the colony. UF/IFAS reports that bait-fed workers die several weeks after exposure and colony elimination takes about three months. Above-ground stations can also be placed directly on active sites inside a building or tree, which matters for aerial colonies.
• Liquid termiticides. Products applied to the soil, injected through the slab or into cracks and wall voids protect the treated zone, though UF/IFAS notes they are unlikely to eliminate colony activity in the surrounding area.

Toro’s termite control service starts with a free inspection in which a trained technician identifies the species and checks how far the activity goes. For subterranean termites such as the Formosan, Toro installs the Sentricon baiting system around the property, with no drilling into the slab and no trenches. Termites carry the bait to the colony, which is designed to eliminate it, including the queen, and the stations stay in place for year-round protection. Our technicians are trained at the TORO Institute alongside Toro’s on-staff entomologists, and the work is backed by the 110% Satisfaction Guarantee. To learn how those stations are maintained, read how often termite bait stations should be checked.

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Frequently Asked Questions

Educational content. This article is for general information about pests in South Florida and is not medical, legal or professional advice. If you have a bite, sting or allergic reaction, contact your doctor; in an emergency, call 911. Pest problems vary from home to home, so a licensed professional should inspect before treatment. When using any pesticide, always read and follow the product label.

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