(adapted from NSW Office of Environment & Heritage article)
Due to habitat loss, possums sometimes resort to living in roofs or chimneys of houses, garages or sheds. If a possum has made its home in your roof, follow these steps to remove the possum and ensure that it does not return.
1. Provide an alternative home for the possum by constructing a sturdy, weatherproof possum box.
2. Where possible, get inside your roof and locate the possum’s nest. The nest, which has the scent of the possum, should be placed in the new possum box to encourage the possum to its new home.
3. Securely fix the possum-house to a tree in or near your yard. Place it at least 4 metres (12 feet) from the ground so the possum will be out of reach of domestic cats and dogs.
4. To encourage the possum to investigate its new home, put half an apple or banana in or near the possum box.
5. Trim any branches that overhang the roof to remove access to your roof.
6. Spread some quassia chips throughout the roof cavity to repel the possum. These can usually be found at hardware stores, or a local pharmacy.
If you can’t find quassia chips, you could repel the possum by spreading eight blocks of camphor or one or two boxes of mothballs throughout the roof cavity. Do not use both camphor and moth balls as they react chemically with each other.
7. Place a light in the roof cavity and keep it switched on for 3 days and nights. The combination of the light and the smell should drive the possum out of your roof and hopefully into the possum box you have provided.
8. If you do not hear the possum for a few nights, it has probably found a new home. To prevent the possum from returning, block off the access points into your roof with timber, chicken wire or both. Night-time is the best time to block off the access points as the possum will have left to forage for food. Do not block off the access points unless you are certain the possum or possums have left your roof.
If this does not deter the possum, it may need to be trapped. Note that under the National Parks and Wildlife Act 1974, it is illegal to kill or catch and release possums without a licence. To apply for a licence and read the conditions which apply, visit the NPWS Possum Management Policy.
An excellent article with more information about possums is available on the Qld Dept of Environment and Heritage Protection website.