How Do You Find Where Ants Are Entering Your House?

Trace It Outwards, Not Inwards

Find the column indoors and follow it in the direction the loaded ants are travelling — the ones carrying something are going home. Keep following. It will run along a skirting, up or down a wall, and out through a gap you would not have found by searching.

Do this in the warm part of the day when the trail is busiest. A trail at seven in the morning can be almost invisible and the same trail at two in the afternoon is obvious.

The Usual Entry Points

The threshold under a patio or back door, particularly where a sliding track meets the frame. The joint where a conservatory or extension meets the original wall. Around a window frame at the sill. Under the sink where the waste pipe passes through. Air bricks. And any crack in render or mortar at ground level.

Ants get through gaps far too small to see, so it is generally more productive to watch them go than to inspect the brickwork.

Then Keep Going, and Find the Nest

Outside, the trail usually runs along the base of the wall, across a path, or along the edge of a border. Follow it to where the ants disappear into the ground.

The classic locations: under paving slabs and block paving, in the sand bed beneath a patio, against a warm south-facing foundation, under a doorstep, at the edge of a lawn, and under a pot or a log that has not been moved. Lift a slab that has fine soil pushed up between the joints and you have usually found it.

The Signs That Point at a Nest Before You See It

Fine granular soil pushed up between paving joints or at the base of a wall. A patch of paving where the mortar keeps washing out. Grass thinning in a small dry patch. And a two-way column that stays in the same place day after day rather than wandering.

A colony under a patio can be very large and completely invisible from above, which is why people are surprised by how many ants come from a garden that looks fine.

What Finding It Changes

Everything. Treating indoors while the nest sits under the back step is a weekly job all summer. Treating the nest is a one-off. Gel bait works precisely because the workers carry it home, which is why the trail needs to stay intact rather than be sprayed.

It is also why the flying ants in July are not a separate problem — those are the same colonies producing new queens. It is a sign of a mature nest nearby, not an invasion.