On slab construction, the University of Missouri Extension says termites commonly enter through expansion joints, cracks, and utility or sewer openings. This checklist walks the slab edge, the openings and the rooms beside the perimeter, so a household can see what to look for before the technician arrives and what to ask about afterwards.
Key takeaways
- The expansion joint where the slab meets the wall is the first place to look.
- Every line that enters the slab, including water, sewer, gas, cable and conduit, is a separate opening.
- Cracks that are still moving should be checked before they are sealed.
- The soil beside the slab edge is part of the route, and a zone is set against it.
- A household can seal small clean gaps, but a sewer penetration or a moving crack is a question for the technician first.
The perimeter: the slab edge and the joints
The slab edge is where a slab house is most readily reached, and the joint where the slab meets the wall or the brick is the first place to look. The check runs the whole perimeter, not only the side that is visible from the street.
Walk the outside of the house once in daylight, and note every joint, every crack and every place where the soil or mulch touches the slab edge. A joint that is open enough to see daylight through, a crack with soil in it or a soft patch of mortar at the brick is a point to record.
Do the same on the inside along the skirting, the flooring edge and the trim. A tube on the outside of the slab edge, or a damp soft spot at the inside skirting, is the sign that a route is in use, and the technician follows it back to the opening it comes from.
- Joint where the slab meets the wall or brick
- Cracks in the slab edge, with soil or mud in them
- Soil, mulch or planting touching the slab edge
- Tubes, soft trim or damp skirting inside the wall
The utility openings: water, sewer, gas and cable
Every line that enters the slab is an opening. The Extension names utility and sewer openings as common entries, so each line is checked on its own, with the soil around it.
The water line enters the slab near the meter or at the wall, and the gap around it is often the first place soil or mud builds up. The sewer line leaves the slab for the public line, and its penetration is the one most households never see. The gas line and the cable or conduit run through the slab edge at their own points, each with a gap that should be checked.
Note each line on a simple sketch of the house, with a mark for the point where it enters, and whether the gap at that point is sealed, open or has soil in it. The sketch is what the technician works from, and it is also what the household keeps for a later question.
- Water line, at the meter or the wall
- Sewer line, where it leaves the slab
- Gas line, where it enters the slab edge
- Cable or conduit, at its entry point
The rooms beside the perimeter
The rooms along the outside walls show whether the route has reached the building. A check of the skirting, the trim and the flooring edge tells the technician where to look next.
The rooms on the exterior walls are checked first, because they are closest to the openings. A soft board at the skirting, a damp patch on the wall, a flooring edge that has lifted or a door frame that has begun to stick are the signs to note. Tap the trim and the skirting, and listen for the hollow sound of wood that has been eaten.
Record which room each sign is in, and how far it is from the outside wall. A sign close to a utility line points to that opening, and a sign in the middle of a room points to a route through the slab.
The soil zone and the drainage
The soil beside the slab edge is the last link in the route. Keeping it clear, and setting a zone where it cannot be kept clear, reduces the number of openings the household has to watch.
Soil piled against the slab, mulch that runs up the brick and a bed that holds water beside the foundation all bring the termites close to the openings. Clear a strip along the edge, lower the mulch below the first course and keep the downspouts discharging away from the wall.
Where the soil cannot be cleared, such as under a patio or against a fence, the technician sets a zone and records its edge. The zone is part of the same sketch as the openings, so the two are read together.
What to do with what you find
Small, clean, stable gaps can often be sealed by the household. A crack that is moving, a gap at a sewer line or any opening that is beside wood should be checked by the technician first.
A small gap at a joint that is clean, dry and not moving is one a household can seal with a flexible sealant, after the technician has said it is safe. Clean the surface first and let it dry. Do not seal a crack that is still opening, since the seal will fail and the gap will reappear.
Do not seal a sewer penetration or any opening that the technician has marked for the builder. Those need a plumber or a builder, and the technician records them as open items so the owner knows they remain.
- Seal: small, clean, dry and stable gaps, after the technician agrees
- Check first: moving cracks, and any gap beside wood or soil
- Leave to a builder or plumber: sewer penetrations and structural openings
Questions to ask after the check
After the check, ask which openings are open, which are sealed, which are inside the zone and which need a builder. Ask for the sketch in writing and ask when the check will be repeated.
The answers form the plan. An opening inside the zone is protected by the soil treatment, an opening outside the zone is a candidate for sealing, and an opening that needs a builder is the owner's to arrange. Ask for the sketch with each of those marked.
Keep the sketch with the building's file, and add each later change to it, such as a new bed, a new line or a repair at the slab edge. A file that is kept this way is the quickest way for a later technician to see the slab's history.
Recording the openings for a later sale
A slab house that is being sold needs its openings recorded so the buyer and the seller see the same list. The sketch and the table below set out a format that a technician can complete on the day.
Use one line per opening: its position on the perimeter, its type, whether it is sealed, open or inside a treated zone, and the date it was last checked. Keep the list with the sketch so the two are read together. A buyer who receives both can see at a glance which openings were examined and which were not.
Where an opening was sealed by the owner, note the material and the date. A later technician can then judge whether the seal was made for a crack that is still moving or for a stable gap, which changes how much weight the seal can bear.
| Opening | Type | Status | Last checked |
|---|---|---|---|
| North-east joint | Expansion joint | Sealed, dated | Date of the sketch |
| Sewer line exit | Utility penetration | Open, builder to address | Date of the sketch |
| Rear door threshold | Crack at the edge | Inside treated zone | Date of the sketch |
Working with a builder or a plumber
Some openings belong to a builder or a plumber, and the checklist should say so rather than leave the owner to guess. A clear hand-off saves a second visit.
Where a sewer penetration needs re-sealing, or a utility line has a gap that cannot be reached from outside, the technician records the work as a job for a plumber or builder. The owner receives the note with the sketch so it can be passed on directly.
If the work is done, the owner adds the date and the trade to the list. A closed item on the list is the best evidence that a gap has been dealt with, and the return visit confirms it.
A brief note on cracks that move
A crack in a slab can open and close with the seasons, and a seal placed on a crack that moves will fail. The check looks for movement before it recommends sealing.
Mark the ends of a suspect crack with a pencil and a date, then look again after several weeks. If the mark has shifted, the crack is moving and the seal should wait. If the mark has not moved, the crack is stable enough to seal once it is clean and dry.
A household that is unsure should ask the technician to check the crack on the visit, since the check is quick and the answer decides whether the seal will hold.
Frequently asked questions
Is a slab house protected from termites?
No. A slab does not stop termites, and the Extension says entry on slab construction is commonly through joints, cracks and utility openings.
Can I seal the cracks myself?
Small, clean, dry and stable cracks can be sealed after the technician agrees. A moving crack, or one near a pipe, should be checked first.
What if a utility line runs through the slab in a place I cannot reach?
It is recorded as a limit on the sketch, with the reason, so the owner knows it was not reached and can ask for a second look.
Sources
This guide is general information for Jackson County homeowners, not a substitute for an on-site inspection. Prices are estimates. See our disclaimer.