How Mice Get Into Melbourne Homes: 8 Entry Points to Check

Mice don’t appear inside by accident. They walk in through gaps you can’t easily see, and they keep coming back until those gaps are closed. Baits and traps deal with the mice already inside, but if the way in is still open, new mice simply replace them. This guide shows the eight places we most often find mice getting into Melbourne homes, what to use (and not use) on each one, and why sealing the gaps is what finally stops the cycle.

How small a gap can a mouse fit through?

A house mouse can squeeze through a gap of about 5 to 6 mm, roughly the width of a pencil. A simple rule: if a pencil fits into a gap, assume a mouse can too. Mice also gnaw at the edges of small holes to make them bigger, so a gap that looks too small today may not stay that way.

The 8 most common entry points in Melbourne homes

1. Weep holes in brick walls

Brick veneer homes, which make up most Melbourne suburbs, have small open gaps along the bottom row of bricks called weep holes. They let moisture drain out of the wall cavity, but they’re also a perfect mouse-sized doorway straight into your walls. Don’t block them with silicone, steel wool or foam. The wall needs them open to drain and breathe. The right fix is a purpose-made, breathable stainless steel weep hole insert that lets air and water out but keeps mice out.

2. Subfloor vents

Older weatherboard, Victorian and Edwardian homes often have subfloor vents that are broken, rusted or missing their mesh. Like weep holes, vents need to stay open for airflow, so they should be covered with fine metal mesh, not sealed shut.

3. Gaps around pipes, cables and air-con lines

Every place a water pipe, gas line, power cable or split-system air-con line passes through a wall is a potential gap. These are among the most common ways in, both from outside and from the wall cavity into kitchen cupboards and laundries. Check behind the stove, under the sink, behind the dishwasher and around the hot water unit.

4. Garage roller doors and side doors

The corners of roller doors, worn bottom seals and gaps under internal garage doors are major entry points, especially in newer estates. Once mice are in the garage, they usually find a way into the house.

5. Roof tiles, ridge capping and eaves

Mice climb well. Loose or broken roof tiles, cracked ridge capping mortar and gaps where the fascia meets the roof give them a direct route into the roof void, where they nest and then move down through the walls.

6. Gaps under external doors

Back doors, laundry doors and doors to the deck often have a gap at the bottom or corners. A properly fitted door seal or brush strip closes them.

7. Gaps where building materials meet

Extensions, renovations and the join between brick and weatherboard, or between a slab and a wall, often leave gaps. These are easy to miss because they’re low down, behind garden beds or hidden by plants.

8. Inside the house: kitchen cupboards and wall cavities

Even when mice get into the walls from outside, they reach your living areas through internal gaps: holes in the back of kitchen cabinets, gaps around pipes under sinks, behind the oven and fridge, and in built-in wardrobes. Blocking these stops mice moving between the wall cavities and your rooms.

What works for blocking mice, and what doesn’t

• Works: metal. Stainless steel mesh, steel or copper wool held in with sealant, metal plates, and cement or mortar for masonry. Mice can’t chew through them.
• Doesn’t work on its own: expanding foam, silicone, plastic, rubber and timber. Mice chew straight through them.
• Doesn’t work at all: peppermint oil, dryer sheets, sprays and ultrasonic plug-in devices. If mice will happily live in roof voids and wall cavities, a smell or a sound won’t keep them out.

Why bait alone doesn’t fix a mouse problem

Bait might get rid of the mice you have today. But if the entry points are still open, new mice move in to replace them, and you’re back where you started. That’s why so many people tell us they’ve “had the house done” before and the mice came back. See why a mouse infestation returns after cheap treatment.

How we stop mice getting in

Our mice treatment is built around entry points, not just bait:

• Exterminate: professional-grade rodenticide placed inside wall cavities and in secured roof void bait stations, away from people, children and pets.
• Track: we map where the mice are moving, nesting and getting into your living areas.
• Block inside, on the same visit: every internal entry point we find is blocked, so mice can’t keep moving between the walls and your rooms.
• Document outside: every external entry point is photographed and documented, with clear guidance on what needs proofing.

The outside entry points are best blocked about 14 days after treatment, once the mice have had time to take the bait and die away from your home rather than being sealed inside. You can do that yourself using our photos, or have us complete the proofing.

A treatment takes a minimum of 1.5 hours. Our mice treatment comes with a 5-year guarantee once the recommended external entry points are blocked, or a Lifetime guarantee when Zeropest completes the proofing. If you choose not to block them, a 3-month guarantee applies. All subject to our guarantee terms.

Mice entry point FAQs

How do I know where mice are getting in?

Look for droppings, grease marks along walls, chewed packaging and gnawed holes, then follow them back towards pipes, cupboards and wall gaps. Droppings under the sink tell you where mice are active, not necessarily where they came in from outside. That’s why we track movement through the whole house and roof void.

Should I block my weep holes to stop mice?

Not with silicone, foam or steel wool. Weep holes need to stay open so the wall cavity can drain and breathe. Use a breathable stainless steel weep hole insert instead.

Can I block the entry points myself?

Often, yes. After our treatment you get photos and notes of every external entry point, and many are straightforward to fix with the right metal materials. Roof work and hard-to-reach areas are best left to us or a qualified tradesperson.

Why shouldn’t I block the outside holes straight away?

If you seal the outside before the bait has worked, mice can die inside your walls or roof. Waiting about 14 days after treatment gives them time to leave first.

Do ultrasonic mouse repellers work?

No. Plug-in ultrasonic devices, peppermint oil and similar deterrents are not a substitute for finding and blocking the entry points.

Hearing scratching in the walls or roof? Call 1800 38 66 55 or request a free quote. We service all of Greater Melbourne, 7 days. More rodent help in our pest guides.