How to Rodent-Proof Your Canberra Home Before Winter

• A mouse can get through a gap of about 8 mm and a rat about 12 mm, so seal the small gaps, not just the obvious holes.
• Work through the six common entry points: door and garage gaps, weep holes and vents, service penetrations, the roofline and eaves, the subfloor, and damaged screens.
• In Canberra, pay extra attention to ducted-heating penetrations and the warm roof void, which are exactly what a rodent wants once the frosts arrive.
• The best time to proof is autumn, before the cold-weather move indoors.
• Homes backing onto reserves, grassland or paddocks face more pressure, so start your check on that side.

Rodent-proofing, also called exclusion, is the part of rodent control that stops the next mouse getting in rather than dealing with the ones already inside. It matters more in Canberra than in most Australian cities, because the capital gets genuinely cold. Hard frosts and sub-zero winter nights push rats and mice to hunt for somewhere warm and dry, and a heated home is the obvious target. The job is to find and close every gap around the outside with materials a rodent cannot chew through, and to do it before the cold sets in.

Canberra adds a couple of local wrinkles. Ducted gas heating is common, which means penetrations through the roof and ceiling and a warm roof void that a rodent will happily move into on a cold night. And as the bush capital, plenty of suburbs back onto nature reserves, grassland and paddocks, so field mice arrive from the fence line rather than the street. Both change where you look first.

Done properly in autumn, proofing lowers the chance of a winter rodent problem far more than any repellent. It works best alongside a professional inspection, both to confirm the home is clear before you seal it and to reach the roof voids, wall cavities and subfloor spaces you cannot safely get to. This guide walks through the method and where Canberra homes are weakest.

Table of Contents:

• Introduction
• What rodent-proofing actually means
• How small a gap can a mouse or rat get through
• Where rats and mice get into a Canberra home
• What to seal the gaps with
• Cutting off food and water
• What you cannot proof yourself
• Technician insights from Canberra homes
• Canberra-specific information
• Practical tips
• Frequently asked questions
• Key takeaways

Introduction

In Canberra, the first hard frost tends to bring the first scratch in the ceiling. It is not a coincidence. When the nights drop below zero and the food outside runs short, rats and mice go looking for warmth, and a heated Canberra home is about the best offer going. The way to avoid that is not to wait until you hear them. It is to close the doors before they arrive.

This guide is about proofing, the practical job of sealing your home against rodents. What it means, how small a gap really matters, where Canberra homes tend to let them in, and how to do it before winter.

What rodent-proofing actually means

Rodent control has two halves. One is removing the rats and mice already on the property with trapping and baiting. The other is exclusion, which is physically closing off how they get in. Baiting without proofing clears the current lot but leaves the door open for the next, especially through a Canberra winter when the pressure to come indoors is constant. Proofing is what turns a treatment into a lasting result.

How small a gap can a mouse or rat get through

This is the figure that catches people out. A house mouse can pass through a gap of about 8 mm, roughly the width of a pen. A rat needs only about 12 mm, close to the width of a thumb. So when you proof, you are not hunting for holes. You are hunting for gaps, including ones you would swear are far too small.

Where rats and mice get into a Canberra home

Walk the outside of the house slowly and check these six areas. Start on the side that faces a reserve, paddock or open grassland if you have one.

Ground-level gaps and doorways

Gaps under external doors and worn seals on garage roller doors are the most common way in. If you can slide a pen under a door, a mouse can follow it. Fit a metal or bristle sweep.

Weep holes and vents

Brick-veneer homes, which make up a lot of Canberra’s housing, have weep holes along the bottom course of bricks, and each one is a ready-made mouse door. Cover them with steel mesh rather than blocking them, because the wall needs them to breathe. Treat subfloor and wall vents the same way.

Service penetrations and ducted heating

Every point where a pipe, gas line, electrical conduit or heating duct passes through a wall, ceiling or roof usually has a gap around it. Ducted gas heating is worth special attention in Canberra, because the penetrations run into the roof void and the warmth around them is exactly what draws a rodent up there in winter.

The roofline and eaves

Rats climb, so check the eaves, any lifted or broken tiles, and the points where pipes meet the roof. A warm roof void above ducted heating is a prime target, so seal the ways into it. Trim back branches that touch the roof or gutter and act as a bridge.

The subfloor

Older homes across the inner north and south sit on footings with subfloor vents, and the mesh is often rusted or torn. This is a common route under the floor and up into wall cavities, and it is usually the first place field mice try on a property backing onto grassland.

Damaged screens and seals

Torn flyscreens, perished door and window seals, and gaps around the meter box are small on their own but add up. A cold Canberra winter finds every one of them.

What to seal the gaps with

The material matters as much as finding the gap, because rodents gnaw. Foam and tape do not last.