NUMBER 1 ROUTE:
Via the drains
So we’ve established that houses are warm and dry and sewers are full of food
The sewers contain the rat population and that rat population likes to nest and rest within houses
The bit that connects houses to sewers are the drains – and this is where the vast majority of entry routes arise
Most common scenarios are as follows..
Via an uncapped inlet
Cracked clay pipe
Plastic to
clay pipe join
Chewed plastic pipes
Soil vent pipes
Up to around the 1960’s, these were usually cast iron which corrodes quite heavily internally (as this is the unpainted part) and this corrosion allows rats to grip and climb up the inside. They can then emerge out the top of the SVP and enter roof voids under the tiles above the gutter or other such weak spots.
Guttering downpipes
NUMBER 2 ROUTE:
Surface rat activity entering an above ground defect
Surface rat activity can develop where food is available through bird tables, dog/cat food left outside, compost heaps, uncontained refuse etc.
If an opportunity presents itself for rats to gain access to a building fabric, then they will enter for the same reasons sewer rats do – it’s drier and warmer than outside
Most common scenarios are as follows..
Damaged/missing air bricks
Pipe passage points
Gas/electrical intake points
NUMBER 3 ROUTE:
Via a neighbouring property
Most houses will be within a terraced row or block of flats – semi-detached at best.
Depending on the construction of the building, sometimes rats can travel across from one building to another via wall cavities and roof voids or via shared service ducts for blocks of flats.
This is typically a consideration with terraced and semi-detached houses built from 1930 onwards as that’s when cavity walls began to become mainstream and roof voids simply had an internal firebreak rather than a continuation of the party wall through the roofline as with Victorian/Edwardian buildings.