Most of the pest problems we get called out for in Broward and Palm Beach County start at the bottom of the house. Not the attic, not the roofline — the first eighteen inches above and below grade, where the slab meets the block, where the AC line-set punches through the wall, where the hose bib sits in a hole that was cut a half inch too wide fifteen years ago.
Ghost ants find that gap. So do roaches, so do subterranean termites working up from the soil, and so does the humidity that makes a wall cavity comfortable for all of them. A single unsealed penetration is an open door with a welcome mat.
This guide walks the perimeter with you. Where the openings are, how to close them properly, and what else uses those same pathways.
Why the slab is the weak point in a South Florida home
Homes here sit on slab-on-grade or shallow crawl construction. There is no basement to buffer the house from the soil, which means the living space is separated from the ground by a few inches of concrete and whatever seals were done during construction.
Concrete shrinks as it cures. It moves with our seasonal wet and dry swings. It cracks around the perimeter, at control joints, and anywhere a pipe or conduit interrupts the pour. Those are hairline gaps at first. Over ten or twenty years of Florida rain, root pressure, and soil movement, hairline becomes a quarter inch.
A quarter inch is enormous in pest terms. A mouse needs a gap the width of a pencil. A roach needs less. Ants need almost nothing.
The eight openings we find on almost every inspection
Walk your own perimeter with a flashlight and a screwdriver. Probe anything that looks soft or hollow.
- The slab-to-wall cold joint. Where the concrete block sits on the slab edge. Look for a horizontal seam with dirt or ant trails leading into it.
- AC line-set and refrigerant penetrations. Almost always oversized, almost always sealed with a smear of mastic that has dried and pulled away.
- Hose bibs and irrigation lines. The hole is cut for the fitting, then never closed around it.
- Electrical and cable service entries. Same story. Foam gets used, then UV and time turn it to crumbs.
- Dryer and bath vent terminations. Damper flaps stick open. Rodents walk right in.
- Weep holes. These are supposed to be there — they let moisture out of the wall cavity. They also let insects in. They get screened, never sealed.
- Garage door thresholds and side jambs. The single most common rodent entry we document in attached garages.
- Expansion joints in the driveway, patio, and pool deck. Where they abut the house, they route water and insects straight to the foundation.
Sealing the right way
The material matters as much as the effort. We see a lot of homeowner work fail within a season because the wrong product went into the wrong gap.
Hairline cracks in concrete (under 1/8 inch): clean the crack with a wire brush, vacuum the dust, and use a self-leveling polyurethane sealant. Polyurethane stays flexible through the movement that opened the crack in the first place.
Structural or widening cracks: stop and get eyes on it. A crack that is growing, stepping diagonally through block, or paired with sticking doors is a foundation issue. Sealant hides that.
Gaps around pipes and conduit (up to about 1/2 inch): copper mesh or stainless wool packed into the void, then sealed over with polyurethane or a quality exterior caulk. The mesh is the part rodents cannot chew.
Larger voids: hydraulic cement or mortar for masonry, backer rod plus sealant for wide joints. Skip expanding foam as a standalone barrier. Rodents chew through it and roaches nest in it.
Weep holes: stainless steel weep-hole covers. They keep the drainage path open and shut out the insects.
Doors: new sweeps and a rodent-resistant garage door seal. This is the highest-return hour you will spend on the whole list.
Do this work dry. Two consecutive rain-free days is the minimum for most sealants to cure properly, which in our climate means planning around the afternoon storms from June through September.
Moisture is the multiplier
Sealing has a second payoff. Every gap you close is a gap that stops moving humid outside air into the wall cavity and the crawl space.
Damp framing draws subterranean termites, carpenter ants, and springtails. It feeds the mold that follows them. Roaches and silverfish orient toward humidity the same way they orient toward food. Bring the moisture down and the habitat value of your foundation drops with it, which is the part of pest control that keeps working after the technician drives away.
Pair the sealing work with grading that carries water away from the house, downspout extensions that discharge at least four feet out, and a vapor barrier if you have a crawl space.
The hazard that uses the same pathways
There is one more thing that travels through foundation cracks, sump pits, and utility gaps, and it is the only one on this list you cannot see, smell, or taste.
Radon is a radioactive gas released by the natural decay of uranium in soil and rock. As warm air rises inside a house, it creates a slight vacuum — the stack effect — that pulls soil gas up through the same openings the ants are using.
The EPA identifies radon as the second leading cause of lung cancer in the United States, responsible for roughly 21,000 deaths a year. Roughly one in fifteen U.S. homes has an elevated level. Because it is colorless, odorless, and tasteless, testing is the only way to know. Short-term kits and lab-analyzed tests are both widely available, and the Florida Department of Health maintains county-level radon data worth looking at before you assume your area is clear.
The EPA action level is 4.0 pCi/L. Below it, the crack sealing described above reduces entry along with everything else. At or above it, the home needs an active system rather than sealant alone.
The standard solution is Active Soil Depressurization. A certified installer runs PVC piping beneath the foundation slab and connects it to a dedicated inline fan that continuously draws soil gas from under the structure and exhausts it above the roofline before it reaches living space. The fan does the work, so the equipment quality determines whether the system holds pressure for years or becomes a maintenance item. Specialists like Festa Radon Technologies build the high-performance mitigation fans that professional installers rely on for exactly that reason.
Radon mitigation and pest exclusion are separate trades. They share a diagnosis: your house is connected to the soil in more places than the builder intended.
Where we come in
On Demand Pest Control inspects the full perimeter as part of every service. We document the openings, seal what belongs in a pest exclusion scope, and tell you plainly when something is a foundation, drainage, or radon question that belongs to another specialist.
If ants keep showing up in the same room, or you are seeing rodent evidence in the garage, the entry point is findable. We will find it.
Schedule an inspection or call us at (954) 947-0805.