Air Bricks and Vents
These can be covered using fine wire mesh to allow air to circulate but prevent pests from entering. This is especially important if they are damaged.
Fitting bristle or brush strips to the bottom of doors will prevent prevents entry, this is highly recommended if you live in an older property as the door fit may not be snug. They will also use cat flaps to get in and will enlarge gaps by gnawing to enter homes via integral garages.
Drains and sewer pipes
Rats have been known to swim up damaged sewer pipes and get round u-bends in toilets. They will also use drain pipes and drainage outlets. Use tightly fitting metal grates or screens to cover drains, especially in basement areas.
Fix damaged roofing and use wire mesh to seal any gaps.
Gaps in exterior walls
Holes or small openings (around utility cables or pipe work) need to be filled with stainless steel wire wool and caulking or concrete. Steel or aluminium plating can be used. Rats can jump, so check up to a height of about 4 feet.
These are often made in exterior walls for cables and pipes, check that old pipework holes are sealed too.
Keep grass mown short to reduce shelter and seeds for food. Ideally leave a gap between the building foundations and the garden.
Seal holes around existing or new pipes with coarse grade stainless steel wire wool and caulking (pliable sealant).
Rats & Squirrels will climb along electrical cables or use overhanging branches to get into loft spaces and attics through gaps in broken roof tiles or under eaves. Repair roof damage and use wire mesh to seal gaps.
Trim tree branches back from the house and where possible avoid plants growing up the sides of your property. Vines, shrubs or over hanging branches can be used for mice to get onto roofs. Overgrown vegetation close to the walls will offer shelter and potential nesting sites.