Why new houses get ants

New houses get ants because building and landscaping disturb existing colonies, bring in soil and plants that may carry nests, and leave gaps around slabs, cladding and service penetrations that haven't been sealed. Concrete slabs and long runs of paving, which Landcare Research calls ant highways for Argentine ants, add warm, sheltered routes. Most new-build ant problems are cleared with one good treatment plus sealing the entry points.

Where the ants come from

New subdivisions are built on land that already had ants. Earthworks disturb colonies, which then look for new shelter, and the nearest shelter is a new house. Argentine ants, already widespread in Auckland, spread through moved soil and materials; Landcare Research notes that most of their spread comes from people moving them rather than natural dispersal.

Landscaping is the other big source. Topsoil, mulch, bark and potted plants delivered to a new section can carry nests. Auckland Council's advice on checking plants and soil before moving them applies to landscapers as much as homeowners. See moving plants and soil.

Slabs and paving

Most new Auckland homes sit on concrete slabs with concrete or paved paths and driveways around them. The slab edge, where concrete meets soil, is warm and sheltered and makes a natural ant highway. Trails run along it to door thresholds, the garage and service entries. Pavers bedded on sand add easy nest sites right beside the house.

Landcare's description of concrete as ant highways, where surface sprays break down fast, explains why trails in new subdivisions can be so long and so stubborn.

Cladding cavities and joinery

Modern Auckland houses have a drained cavity behind the cladding, designed to let water escape. It also gives ants a sheltered route around the whole house. Aluminium window and door joinery has drainage slots and gaps at the corners. Garage doors have gaps at the base and sides. Each is a potential door.

These aren't defects; they're how the building is meant to work. But they mean ant treatment in a new house focuses on the base of the cladding, joinery and service entries rather than just the kitchen.

Service penetrations

Every pipe, cable, duct and vent that passes through the walls or slab creates a gap. Heat pump lines, the hot water cylinder, outdoor taps, gas lines, the meter box, internet and power cables and the bathroom extractor all need holes. If these aren't sealed well, ants use them. Checking and sealing service penetrations is one of the most useful things you can do in a new house.

Builder or owner?

If ants are coming through unsealed gaps that should have been sealed as part of the build, it's reasonable to raise it with the builder, particularly within any defects or maintenance period in your contract. The ants themselves are usually treated as the owner's responsibility. It's worth photographing where trails enter before anything is treated or sealed.

Under the Consumer Guarantees Act, services must be carried out with reasonable care and skill. For contract specifics, check your building contract or get advice.

What to check first

• trails along the slab edge and into the garage
• door thresholds and the bottom of sliding door tracks
• window corners and drainage slots
• gaps around pipes and cables, especially heat pump lines
• garden beds and mulch hard against the cladding
• newly planted pot plants and shrubs near doors

Treatment and sealing

A technician treats the outside entry points and travel routes with a non-repellent product, places bait on active trails inside and out, and identifies the species. Once the ants are under control, sealing service penetrations and keeping mulch and soil away from the cladding reduce the chance of a repeat. Published Auckland prices for inside and outside of a typical three-bedroom home start at about $340 to $400 incl GST.

Apartments and terraces in new developments are best treated building-wide; see apartments and body corporate buildings.

Checked 5 November 2026