Rodent-Proofing Your Home

Why exclusion matters most

Trapping or baiting removes the rodents that are already inside, but if the gaps they used remain open, new rats and mice move in to take their place — often within weeks. Rodent-proofing (exclusion) closes those routes. Combined with removing food and shelter outside, it is the only approach that gives lasting results.

Rodents are also cautious and habitual. They use the same routes night after night, leaving greasy rub marks, droppings and gnaw marks. Those signs tell you exactly where to look.

Know which rodent you have

• House mouse: small (6–10 cm body), large ears, droppings 3–6 mm. Explores new objects, stays close to its nest, nests in walls, cupboards and appliances.
• Roof rat: slender, pointed snout, large ears, tail longer than its body, droppings about 10–12 mm. Climbs expertly and nests high — roofs, walls, trees and palms. The usual rat in ceilings in coastal cities.
• Norway rat: heavy-set, blunt snout, small ears, tail shorter than its body, droppings about 18–20 mm. Burrows at ground level under slabs, sheds and along creeks and drains.

If you are unsure, see how to tell a rat from a mouse. The answer changes where you look: roof rats mean checking the roofline and vegetation; Norway rats mean checking ground-level gaps and burrows; mice mean checking every small gap.

How small is too small?

Rodents can pass through any gap their head fits through. As a guide, mice can pass through gaps of about 6 mm and young rats through about 12–15 mm. If a pencil fits through a gap, assume a mouse can too. Rats and mice can also gnaw to enlarge small openings in soft materials such as timber, plastic, rubber and foam.

Materials that work (and those that don’t)

Use

• Galvanised or stainless steel mesh with a small aperture (6 mm or less) for vents and larger gaps.
• Steel wool or copper mesh packed firmly into gaps, then sealed over with a suitable sealant.
• Metal flashing, kick plates and brush strips at door bases and garage doors.
• Cement-based fillers and mortar for gaps in masonry.
• Purpose-made weep-hole covers and eave or gutter guards designed to stop rodents.

Avoid on their own

• Expanding foam, soft silicone, plastic mesh and timber offcuts — rodents chew through them.
• Blocking weep holes or vents completely, which traps moisture in walls and sub-floors.

Where to check

Roofline

• Gaps where the lowest row of tiles meets the gutter, and under ridge capping where mortar has cracked.
• Gaps under metal roof sheets at the eaves.
• Branches, vines, palms and power lines touching the roof.

Walls

• Pipe and cable penetrations, especially air-conditioning lines, gas lines and hot water connections.
• Gaps where extensions meet the original house.
• Vents and weep holes without covers.

Ground level

• Door bases, garage doors and roller doors.
• Gaps in slabs and around drainage pipes.
• Burrows along paths, retaining walls, sheds and compost bins.

Inside

• Gaps around pipes under sinks and behind the dishwasher, washing machine and fridge.
• Kitchen kickboards and the backs of cupboards.

Remove food and shelter outside

Exclusion will not hold for long if the property feeds and shelters a large rodent population. See making your property less attractive to rats.

• Harvest fruit promptly and pick up fallen fruit and nuts.
• Store pet food, bird seed and poultry feed in metal or hard plastic bins.
• Feed pets and chickens in the morning and remove leftovers before dark.
• Use enclosed, rodent-resistant compost bins and avoid adding meat or dairy.
• Stack firewood and materials off the ground and away from walls and fences.
• Thin dense groundcovers, bamboo and palm fronds near the house.

Signs you have rodents

Rats and mice are mostly active at night, so you are more likely to see what they leave behind than the animals themselves. Common signs include:

• Droppings: mouse droppings are about the size of a grain of rice; rat droppings are larger, up to the size of a jelly bean. Fresh droppings are dark and soft.
• Gnaw marks on food packaging, cables, timber and plastic.
• Rub marks: dark, greasy smears along walls, beams and around holes, left by fur.
• Noises in the ceiling or walls at night: scurrying, scratching or gnawing.
• Nests of shredded paper, fabric or insulation in roof voids, cupboards, garages and stored boxes.
• Burrows in garden beds, under compost bins or along fences.
• Pets staring at walls, scratching at cupboards or becoming unusually interested in one spot.

Heavier sounds, especially thumping or walking, are more likely to be a possum. See what the noise in my ceiling at night is.

Native rodents and other animals

Australia has many native rodents, such as bush rats, water rats (rakali) and native mice, and they are protected. They are less likely to live inside homes than introduced black rats, brown rats and house mice, but they can visit gardens near bushland and creeks.

Antechinus, small native marsupials that look like mice, sometimes shelter in roof voids and sheds in cooler months, particularly near bushland. They are also protected. If you live near bushland and are unsure what you have, look closely at a photo before setting traps or bait, and contact your state wildlife authority or a licensed wildlife catcher for advice. Exclusion, by sealing the entry point once the animal has left, works for all of them.

Trapping and baiting

Snap traps set along walls and runways, where droppings and rub marks show activity, are effective and avoid poison risks. Place traps at right angles to the wall with the trigger facing it. Rats are wary of new objects, so leave traps baited but unset for a few nights first; mice are curious and are often caught quickly.

Rodenticides must be used exactly as the label directs, in tamper-resistant bait stations where required. Secondary poisoning of pets and wildlife, such as owls that eat poisoned rodents, is a real risk, and poisoned rodents can die in wall and roof voids and cause odour. For these reasons many households and professionals prefer trapping and exclusion.

Wear gloves when handling traps and dead rodents, and do not sweep or vacuum dry droppings, which can raise dust. Dampen them with disinfectant first, then wipe them up.

Health and safety

• Rats and mice can spread diseases such as leptospirosis and salmonellosis through urine and droppings.
• In Queensland and NSW, rats carry rat lungworm, which can infect people and dogs through slugs and snails. Wash produce and supervise children and dogs around snails.
• Gnawed electrical wiring in roof voids can create a fire risk.
• Possums are protected wildlife. If the noise in your roof is a possum, it must be managed according to state rules, usually by a licensed catcher, and must never be baited.

Cleaning up safely

After rodents have been removed, clean up droppings, urine and nesting material carefully:

• Ventilate the area first if it is enclosed, such as a shed or roof void.
• Wear disposable gloves and, for large amounts, a P2 mask.
• Spray droppings and nests with disinfectant or a diluted bleach solution, and leave for several minutes.
• Wipe up with paper towels, seal everything in a plastic bag and put it in the household rubbish.
• Disinfect surfaces, then wash your hands thoroughly.
• Throw out any food that rodents may have touched, and wash food-contact surfaces.

Don’t sweep or vacuum dry droppings, because it raises dust.

Cars, sheds, chickens and aviaries

• Cars: rodents shelter in warm engine bays and can chew wiring, which can be expensive to repair. Cars parked for long periods near food sources are most at risk. Check under the bonnet if a car has been parked for a while, and remove food and rubbish from garages.
• Sheds and garages: store items on shelves off the floor, in sealed plastic tubs rather than cardboard, and keep doors closed or fitted with seals.
• Chickens and aviaries: spilt feed is one of the biggest rodent attractants in suburban yards. Use a treadle or rodent-resistant feeder, collect eggs daily, store feed in metal bins, and clean up spilt seed each evening. Fine wire mesh around coops and aviaries, buried at the base, keeps rodents out.
• Compost: use enclosed bins on a mesh base, and avoid adding meat, dairy and cooked food.

When to get professional help

Consider professional help if you cannot safely access the roof void, if activity continues after trapping and sealing, if entry points are high on a two-storey home, or if you suspect wiring damage. Sealing roof entry points is often a job for a roofer working alongside a pest manager.

Local detail: rats and mice in Brisbane and winter pests in Brisbane.

Answers related to this guide

• How Are Mice Getting Into My House?
• Why Are Rats in My Roof?
• Can Rats Get Through Roof Tiles?
• How Do I Make My Property Less Attractive to Rats?
• How Do I Tell a Rat From a Mouse?
• What Is the Noise in My Ceiling at Night?
• Why Are Rats Coming Inside During Winter?

Local information

• Rats and Mice in Brisbane

Pests in this guide