Most ants that come inside are commuting: they nest in the garden and visit the kitchen. A nest inside the structure of the house is a different problem, because you can't reach it, you can't see how big it is, and anything you spray at the exit points only moves the ants along to the next gap.
Signs the nest is in the house
- Ants appear from power points, switch plates, light fittings or ceiling roses.
- Trails run down from the top of a wall or a window frame rather than in from a door.
- Ants show up in a bathroom or upstairs room with no obvious route from outside.
- Small piles of fine debris appear under skirting boards or window sills.
- Winged ants emerge indoors.
The usual suspect: white-footed house ants
In Auckland, ants living inside the walls are very often white-footed house ants: small, black or dark brown, with pale feet. Landcare Research notes that they nest in the wall cavities of buildings, can build up to very high numbers there, and that their workers don't pass food to one another the way most ants do. That single habit is why shop baits so often disappoint: each worker eats what it finds, so a little bait reaches very few ants. Argentine ants can also move into wall cavities, especially in older timber houses, and are handled differently (see treating Argentine ants).
How a pest controller treats a cavity nest
- Map the exits. Every place ants come and go is noted: switch plates, light fittings, gaps at cornices, window reveals, outside weep holes and cladding joins.
- Bait at the exits, generously. Gel bait is placed in the gaps where ants emerge, in larger amounts and more spots than you would use for other species, and topped up if they clear it.
- Treat the outside walls. A non-repellent product around the base of the walls, window frames and service entries catches workers going in and out.
- Leave the cavities alone where possible. Drilling or dusting into a wall is only done when needed and by someone who knows what's behind it. Electrical fittings should only be opened by a licensed electrician.
- Come back. Cavity nests often need a second round a few weeks later.
Timber, villas and newer homes
Older villas and bungalows have open framing, sub-floor spaces and lots of small gaps, so ants travel through the structure easily. Newer homes with sealed linings have fewer entry points, but service penetrations, recessed downlights and cladding cavities give ants plenty of room. The approach is the same: find the exits and get bait to them. If you see winged insects or damaged timber, mention it; a pest controller can rule out termites or borer at the same visit.
What you can do meanwhile
- Keep food sealed and benches clear so the ants take the bait when it's placed.
- Note where and when you see them, with photos. It shortens the inspection.
- Don't block the exits with sealant yet. Ants will make new ones, and the technician needs the existing ones to place bait.
Ant control questions
Will the technician need to cut holes in my walls?
Rarely for ants. Most cavity nests are treated through the gaps the ants already use. If access is needed, they should explain why and get your agreement first.
Are ants in the walls a sign of structural damage?
Not usually. The ants that nest in walls in Auckland homes don't eat timber. Damage, soft timber or frass is more likely to be borer or rot, and is worth checking separately.
Why do the ants keep coming back to the same power point?
It's one of their exits from the cavity, and the colony is still alive. Bait placed there, and kept topped up, is the most direct way to reach them.
Where these facts come from
Checked 27 October 2026