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- In a terrace, the weak points are shared: a continuous roof cavity along the row, party walls, subfloor vents and perished mortar in old brickwork.
- In an apartment, rodents travel through common property, so risers, garbage rooms, car parks and shared wall cavities matter as much as your own front door.
- A mouse needs a gap of about 8 mm and a rat about 12 mm, so seal the small gaps in old brick, not just the obvious ones.
- Seal your own lot with gnaw-resistant materials, but for shared pathways in strata you will need the owners corporation on board.
- On a heritage terrace, use discreet mesh and matching repointing rather than cement or foam, and check council rules before altering a facade.
Rodent-proofing a freestanding house is one thing. A Sydney terrace or apartment is harder, because the building is shared. A terrace sits in a continuous row with party walls and, very often, a single roof cavity running the length of the block, so a rat that gets in three doors down can reach your ceiling. An apartment shares wall cavities, service risers and common areas with every other unit, which means the gap that lets rodents in is frequently not even inside your lot.
Sydney’s warm climate and leafy inner suburbs suit roof rats, the black rats that climb fences, branches and powerlines straight into roof spaces. Older brick and sandstone terraces add perished mortar, open subfloor vents and worn sash windows to the mix. Apartments add risers, garbage rooms and basement car parks. The proofing job is the same in principle, find and close the gaps, but the map is different for each.
You can do a lot yourself inside your own lot. The parts you cannot reach or cannot control alone, the shared roof cavity, the common property, the building’s risers, are where a professional inspection and, in strata, the owners corporation come in. This guide walks through both property types.
Table of Contents:
- Introduction
- Why terraces and apartments are different
- How small a gap can a rat or mouse use
- Rodent-proofing a Sydney terrace
- Rodent-proofing a Sydney apartment
- What to seal the gaps with
- Cutting off food and water
- What you cannot proof yourself
- Technician insights from Sydney homes
- Sydney-specific information
- Practical tips
- Frequently asked questions
- Key takeaways
Introduction
If you live in a Paddington terrace or a Surry Hills apartment, you have probably heard the advice to seal gaps and keep food covered. It is good advice, and it is also written for a standalone house on its own block. Terraces and apartments break that model, because the thing letting rodents in is usually shared with your neighbours.
Once you understand that, proofing stops being a losing battle against gaps you cannot find and becomes two clear jobs. First, close everything you can control inside your own place. Second, work out which pathways are shared, and get the right people involved to close those too.
Why terraces and apartments are different
A rodent does not respect the boundary of your lot. In a terrace row, the roof cavity is often one long space above several homes, and party walls have gaps at the top where they meet the roof. In an apartment block, the wall and ceiling cavities, the plumbing and electrical risers, and the common areas all connect the units together. This is why a single unit can do everything right and still hear scratching. The entry point belongs to the building, not the home.
How small a gap can a rat or mouse use
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. In an old Sydney terrace, that means a perished mortar joint or a cracked airbrick is a doorway, not a cosmetic flaw. It is worth knowing which rodent you are dealing with, and our roof rat page explains the climber behind most Sydney roof activity.
| Rodent | Smallest gap | Common in Sydney because |
|---|---|---|
| House mouse | about 8 mm | squeezes into kitchens and wall cavities |
| Roof rat (black rat) | about 12 mm | climbs branches, fences and wires into roofs |
| Norway rat | about 12 mm | comes up from drains and burrows after heavy rain |
Rodent-proofing a Sydney terrace
The shared roof cavity and party walls
This is the one most people miss. Many Victorian terrace rows share a continuous roof space, and party walls often stop short of the roofline. Sealing the gaps where your ceiling meets the party wall, and checking the roof for lifted tiles and gaps at the parapet, matters more here than on a detached house. If the row shares a roof cavity, lasting control usually needs neighbours involved too.
Subfloor vents and old mortar
Terraces on brick or sandstone footings have subfloor vents and airbricks, and after a century the mortar joints perish and crack. Mesh the vents with stainless or galvanised steel behind them so air still moves, and have loose or missing mortar repointed. Do not block vents solid, because Sydney’s damp will follow.
The street front and the rear lane
Terrace front doors often open straight onto the footpath with a worn gap underneath, so fit a door sweep. At the back, courtyards and rear lanes bring bins, drains and clutter close to the wall, which is exactly what a rat wants. Keep bins lidded and clear of the wall, and seal the gaps where a rear addition meets the original structure.
Heritage-safe materials
On a heritage terrace you cannot simply cement everything. Use discreet stainless mesh, reversible fixes and matching mortar for repointing, and keep the original brick and sandstone intact. If your terrace sits in a heritage conservation area, check with council before altering the facade.
Rodent-proofing a Sydney apartment
Your lot: what you can seal yourself
Inside your own unit, close the gaps around pipes under the kitchen and bathroom sinks and behind the dishwasher and washing machine, where plumbing enters the wall cavity. Fit a sweep to the front door if there is a gap to the corridor. Check balcony penetrations for the air-conditioner and any drainage. These are the entry points you control.
Common property: the pathways you cannot seal alone
Rodents move between units through service risers, shared wall and ceiling cavities, the garbage room or chute, and the basement car park up into the lift lobby. You cannot proof these on your own, and sealing your unit while the riser stays open only moves the problem next door. In a strata building, pest control on common property is generally the owners corporation’s responsibility, while inside your lot it usually falls to you. If rodents are getting in through shared areas, raise it with your strata manager or committee as a building-wide issue.
What to seal the gaps with
Rodents gnaw, so the material matters. Foam and tape do not last. On heritage brick, match the repair to the building.
| Entry point | Best fix | What to avoid |
|---|---|---|
| Perished mortar joints | Repoint with a matching mortar | Silicone or foam in the joint |
| Subfloor and wall vents | Stainless or galvanised mesh behind the vent | Blocking the vent solid |
| Pipe penetrations | Steel wool packed tight, then sealed | Expanding foam on its own |
| Gap under a door | Metal or bristle door sweep | Rubber strip alone |
| Roof and party-wall junctions | Mesh and flashing, or a roofer | Leaving gaps at the parapet |
| Heritage facades | Discreet, reversible mesh, heritage advice | Cement render over original brick |
Cutting off food and water
Sealing works better when the food goes too. Keep bins lidded, store dry goods and pet food in solid containers, clear fallen fruit from courtyards, and fix leaking taps. In a block, a poorly managed garbage room feeds the whole building, which is another reason to raise waste management with strata. For species and health detail, see our rodent identification pages.
What you cannot proof yourself
Two jobs sit outside a homeowner’s reach. First, shared roof cavities, wall spaces and any common property in a strata block need a coordinated approach, not a single unit acting alone. Common signs you already have rodents include scratching noises in walls or ceilings, droppings, gnaw marks, greasy rub marks along surfaces, nests made from shredded materials, and a persistent musky odour. Second, you should confirm the property is clear before sealing, or you can trap rodents inside a shared wall where they die and become a far worse problem. A professional rodent control in Melbourne works out what is already inside, clears it, and identifies the shared pathways to close, which in strata means working with the owners corporation.
Technician insights from Sydney homes
On terraces around the inner west and east, our technicians most often trace activity to the shared roof cavity and to perished mortar down near the subfloor, not to a dramatic hole. In apartments, it is nearly always a service riser, the gap behind a kitchen cabinet where the plumbing runs, or a garbage room that props its door open. The recurring lesson is the same across both. In shared buildings, the entry point is usually on the other side of a wall you do not own.
Sydney-specific information
Sydney’s warm, humid climate and green inner suburbs favour roof rats, which climb fences, fig trees, palms and powerlines into roof spaces year round. Winters are mild rather than cold, but wet spells matter. June alone averages well over 100 mm of rain, and a flooded burrow pushes Norway rats up out of drains and gardens toward dry shelter. For that seasonal side, see our winter rodent guide.
The building stock is the other half of the story. Sydney has a high share of Victorian terraces in suburbs like Paddington, Surry Hills, Glebe, Newtown and Balmain, and one of the highest rates of apartment living in the country. Both share structure with neighbours, which is why proofing here is as much about coordination as it is about caulk.
Practical tips
If you are in a terrace, walk the property once a year.
- Check the ceiling line where it meets each party wall, and the roof for lifted tiles.
- Mesh every subfloor vent and airbrick, and have perished mortar repointed.
- Fit a sweep to the front door and seal where any rear addition meets the original wall.
- Keep courtyard and lane bins lidded and away from the wall.
If you are in an apartment, do this instead.
- Seal the gaps around pipes under sinks and behind appliances.
- Fit a door sweep if there is a gap to the corridor.
- Note any signs near the garbage room, riser cupboards or car park.
- Report shared-area activity to your strata manager or committee in writing.
Frequently asked questions
Why can I still hear rodents after sealing my unit?
Because the entry point is probably shared. In terraces and apartments, rodents travel through party walls, roof cavities and service risers you do not control, so sealing your own space does not always stop them.
Whose responsibility is pest control in a strata building?
As a general rule in NSW, pest control on common property falls to the owners corporation, while inside your own lot it falls to you. If the problem is in a riser, the garbage room or the car park, raise it with strata.
How do rats get into a Sydney terrace roof?
Usually by climbing. Roof rats use fences, branches, vines and powerlines to reach the roof, then enter through gaps at the eaves, lifted tiles or the party-wall junction, often into a roof cavity shared along the row.
Can I block my subfloor vents to stop mice?
No. Vents keep the subfloor dry, which matters in humid Sydney. Cover them with steel mesh behind the vent so air still moves but rodents cannot pass.
What size gap can a mouse fit through?
About 8 mm, roughly the width of a pen. A rat needs only about 12 mm. In old brickwork, a perished mortar joint is often enough.
Do I need council approval to rodent-proof a heritage terrace?
For internal and discreet work, generally no. If your terrace is in a heritage conservation area and the work changes the facade, check with your council first.
Key takeaways
- In terraces and apartments the entry point is usually shared, so proofing is part sealing and part coordination.
- Seal to 8 mm for mice and 12 mm for rats, and treat perished mortar as a real gap.
- In strata, common property is generally the owners corporation’s job, your lot is yours.
- Use heritage-safe fixes on old terraces, discreet mesh and matching mortar, not cement or foam.
- Confirm the place is clear before sealing, and get a professional onto the shared spaces you cannot reach.
Living in a terrace or apartment and not sure where they are getting in? Our licensed Sydney technicians will inspect the property, identify the shared pathways, and work with you or your strata to close them. Call Tom’s Pest Control Sydney on (02) 8073 9252 or book a rodent inspection online.
