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Possum or Rat in the Roof? How to Tell What's Making the Noise

Published 7 min read

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Don’t leave this question up to chance. Knowing whether you are dealing with a possum or a rat in your roof is crucial for determining the right path forward.

I have spent 25 years in Sydney pest management and crawled through thousands of roof voids. Many jobs start with a homeowner lying awake trying to work out whether they have a possum or a rat in their roof. You can usually narrow that down yourself, tonight, without going near the manhole.

Key Takeaways

  • Heavy, slow thumps, with one animal leaving around dusk and returning before dawn, point to a brushtail possum.
  • Fast, light scurrying in short bursts all night, from several animals, points to rats.
  • Repeated gnawing or scratching sounds from timber, plastic or electrical cables is far more likely to be rats than a possum.
  • Possum droppings are typically 15 to 25mm cylinders usually found in piles. Rat droppings are usually 12 to 18mm, tapered, and scattered.
  • A rat can use a gap about the width of your thumb. A brushtail possum needs roughly a fist-sized opening.

The 60-Second Roof Noise Test

Here are 5 ways you can begin to evaluate whether you’re dealing with a possum or rats from the comfort of your bed. Keep in mind these are just descriptions of typical behaviour, and may not be accurate in all cases.

1. Timing

Possum: Starts near dusk, one heavy exit, then quiet, back before dawn

Rats: Several short bursts spread through the night

2. Weight

Possum: Thumping, walking, sometimes a dragging or rolling sound

Rats: Light, fast pitter-patter

3. Number

Possum: One animal, occasionally a breeding pair or mother with young

Rats: Several, moving in different directions at once

4. Sound type

Possum: Hissing, guttural growling

Rats: Scratching, gnawing, occasional squeaking

5. Access

Possum: Needs a fist-sized opening, a lifted tile, or an open gable vent

Rats: Needs a gap about the width of a thumb

What a Possum in the Roof Actually Sounds Like

2 possum species live around Sydney homes, and one is far more likely to be in a roof. The common brushtail is cat-sized, heavy, and territorial, and will readily take a roof void over a tree hollow. The common ringtail builds a nest of woven twigs and leaves, called a drey, outside in dense foliage. They rarely come inside.

Because a brushtail is heavy, you tend to hear a walk rather than a scurry. People often describe hearing footsteps. The possum-in-roof noises people report next are vocal sounds including hissing, sharp clicking, a rasping cough, and a deep guttural growl.

A possum usually uses a roof as a daytime den, leaving at dusk to feed and returning before dawn. This often results in one heavy departure shortly after dark and one heavy return before sunrise, usually at roughly the same times each night.

What Rats in the Roof Actually Sound Like

The rat in a Sydney roof is usually the black rat, Rattus rattus, known as the roof rat for exactly this reason. These animals are agile climbers that prefer to live in roofs, cavity walls, and trees. The brown rat, Rattus norvegicus, behaves differently: it burrows and stays low in subfloors, drains, and sewers. So a noise up in the ceiling, rather than under the floor, usually points to a black rat.

The sounds are scratching, scurrying, high-pitched squeaks, and above all gnawing. A rat’s incisors never stop growing, so it gnaws constantly to wear them down. A repeated grinding or splintering noise is one of the stronger pointers towards rats. Rats-in-roof sound patterns also tend to be disorganised. You might hear several bursts across the night, in different directions, which suggests more than one animal.

The Physical Evidence

Droppings

Possum droppings are typically 15 to 25mm long, cylindrical, and left in piles, because possums tend to use the same latrine spot. Rat droppings are smaller, usually 12 to 18mm, tapered at both ends, and scattered along the beams and pipes they run nightly. 

Do not sweep or vacuum dried droppings, as this can disturb dust and other airborne particles. Wear appropriate PPE and dampen the droppings before carefully cleaning them up.

Damage

Rats tend to leave gnaw marks on timber, plastic, and cable sheathing, plus dark greasy rub marks where they brush the same beam nightly. The clearest signs of possum activity are nest bowls made of crushed insulation, and heavy urine staining that shows through the ceiling as a spreading brown patch.

Chewed cable sheathing is very rarely anything but rats, but possums do sometimes gnaw timber around an entry point.

Entry Points

Rats can use a gap roughly the width of a thumb. Possums need something closer to a fist-sized opening, such as a lifted tile, a rotted eave, or an open gable vent. Both often use overhanging branches, which is often how rats get into roof spaces.

To test an entry point, the NSW Government recommends dusting a fine layer of plain flour near the suspected opening and analysing it in the morning. A possum leaves a hand-like print with five long toes. A rat leaves a small print, often with a tail drag through it.

Why Getting This Right Matters More Than People Think

If it is a possum, using rodent bait is both ineffective and illegal. Possums are protected in NSW under the Biodiversity Conservation Act 2016, and intentionally poisoning one is an offence.

A poisoned possum rarely leaves the roof space. Instead, it may die inside a wall cavity or roof void where it cannot be easily retrieved, often resulting in unpleasant odours that can linger for days or even weeks, particularly during warm weather.

If it is rats, delaying treatment allows the infestation to grow. Rats reproduce quickly and can cause significant damage by gnawing electrical cable sheathing, timber and plastic plumbing, increasing the risk of costly repairs and, in some cases, electrical fires.

The Law on Possums in NSW

Possums are protected native animals under the Biodiversity Conservation Act 2016 (NSW). Catching and releasing one requires a NSW Catch and Release Possum Licence, and without that licence it is prohibited. If you don’t have a licence, get in touch with a pest control professional who does.

Even with a licence, there are strict requirements for how a possum must be released. It must be released at dusk, within 150 metres of where it was captured, on the same property, and next to a tree or other structure it can immediately climb.

NSW Environment and Heritage recommends installing a suitable nest box nearby before excluding the possum. The nest box should be securely mounted at least four metres above the ground, with some of the possum’s nesting material placed inside to encourage it to use the new shelter.

Another method is to allow the possum to leave the roof naturally after dusk, then install a one-way exit door over the entry point. Once you’ve confirmed the possum is outside, permanently seal the entry point and any other access points. If the possum returns, another entry point has been overlooked.

If the animal is injured, orphaned, or distressed, contact WIRES.

What You Can Do Tonight, and What You Should Not

Do:

  • Sit outside at dusk with a clear view of the roofline. A possum denning up there should leave to feed, and you may see where it comes out, helping you identify its entry point.
  • Run the flour test at the suspected entry point.
  • Write down the times you hear activity for 2 or 3 nights. The timing and pattern of movement can provide valuable clues.
  • Walk the perimeter and and look for tree branches touching the roof, damaged eaves, lifted roof tiles or other potential entry points.

Do not:

  • Lay bait before you are 100% confident the animal is a rat.
  • Trap a possum. A licence is required in NSW, and this is one job that is not worth doing yourself.
  • Seal the entry point until you are certain the animal is out, remember there may be more than one animal in there. This is the mistake that turns a nuisance into a dead animal in your ceiling, and the one I see most often.
  • If you have no experience working in roof voids, don’t climb into one yourself. Poor footing over ceiling joists, live electrical wiring, limited visibility and a cornered animal can quickly create a dangerous situation.

Are you renting or renting out a property? See our guide on who pays for pest control in an NSW rental.

When You Need a Licensed Professional

If you have rats in your roof, you need a rodent management program. This can include targeted baiting or trapping in the void, then proofing every entry point.

If it’s a possum, the focus is on legally excluding the animal from the roof and proofing the entry points to prevent it from returning. In NSW, this work requires a licensed operator, so don’t hesitate to ask to see their Catch and Release Possum Licence before work begins.

If you have completed the roof noise test, inspected for entry points and carried out the flour test but still can’t confidently identify the animal, that’s a good time to stop guessing. A professional inspection can usually identify the pest and recommend the most appropriate course of action.

Frequently Asked Questions

What Time of Night Do Possums and Rats Make Noise?

Possums are usually loudest around dusk and again just before dawn, when they leave and return to the roof. Rats are generally active in shorter, scattered bursts throughout the night. While timing is one of the strongest clues, it should always be considered alongside other evidence such as droppings, gnaw marks and entry points.

Can You Have Both Possums and Rats in the Roof at the Same Time?

Yes. A roof that provides shelter for a possum can also provide ideal conditions for rats, so it’s possible to have both at the same time. If you’re hearing heavy thumping around dusk or before dawn, together with light scratching or scurrying throughout the night, consider the possibility that both species are present.

Is It Legal to Trap a Possum in NSW?

No. Possums are protected native animals under the Biodiversity Conservation Act 2016 (NSW). Unless you hold a current NSW Catch and Release Possum Licence, you cannot legally trap and relocate a possum.

How Long Does a Dead Animal in the Roof Smell For?

A rat usually smells for 1 to 2 weeks. A possum, being much larger, can smell for 4 to 6 weeks, or longer in summer heat.

Do Possums or Rats Cause More Damage?

In most cases, rats cause more damage than possums. They continually gnaw to wear down their teeth, damaging electrical cable sheathing, timber, plastics and stored items. They also contaminate insulation with urine and droppings, creating ongoing hygiene issues and increasing the risk of electrical faults and fires.

Possums generally cause less structural damage, but they can crush insulation, create heavy urine staining, damage ceilings over time and make considerable noise while living in a roof.

How Did They Get In?

Rats can get in through a gap about as wide as your thumb, often a broken tile, a junction where the roof meets a wall, or an unscreened vent. Possums generally need an opening closer to the size of a fist, such as a lifted tile or a rotted eave. Both commonly arrive via a branch touching the roof.

Written by Liam Milligan, licensed pest technician. 25 years in Sydney pest management.

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