It’s fall and cooler temperatures are settling in. That means mice and rats are heading indoors. As rodents look for winter harborage, human dwellings and buildings start to feel the pressure of encroaching rodents.
Agile and adaptable, rodents enter buildings any way that they can. They squeeze through spaces as big as their heads: mice need only 1/4'', young rats, 1/2''. Anywhere a pencil fits through, a mouse can too.
Rodents can enter dwellings in multiple ways. They arrive via ventilation grills, sidewalk gratings and large sidewalk cracks. They gnaw through wooden doors and crawl into spaces where pipes meet wood siding. They scale vertical wires, pipes and tree limbs. Rats burrow under foundations of building lacking basements. Rodents also get into hollow walls between floors and floor sills. They can also hide in pallets and rush in through open doors. They easily come inside through defective drain pipes, travelling inside the pipe or burrowing alongside it.
A series of material will help you keep rodents out of buildings:
1) Galvanized, stainless or other non-rusting metals: a) sheet metal, 24 gauge or higher; b) expanded metal, 28 gauge or higher; c) perforated metal, 24 gauge or higher; and d) hardware cloth, 19 gauge or higher with 1/4'' or less mesh.
2) Cement mortar: 1 part cement, 3 parts sand mix or richer.
3) Concrete: 1 part cement, 2 parts gravel, 4 parts sand mix or richer. Adding broken glass to mortar or cement will deter rodents from burrowing through it as it dries.
EXAMPLES OF RODENT PROOFING
Creative use of materials combined with knowledge of rodent behavior will help you exclude rodents from buildings. Here are a few ways to use the materials for rodent proofing. Patch holes around plumbing with concrete or mortar. Cover a drain, vent or chimney with 1/4'' hardware cloth. Along the bottom of a door, use sheet metal flashing. Place a metal, circular rat guard on a drain to prevent rats from wedging themselves between the building and the pipe to crawl upwards.
Keep an eye out for new holes and tunnels into buildings a week or two after the building has been sealed up. Efforts by rats and mice to return to old feeding grounds will be strongest then.
--From University of Florida Institute of Food and Agricultural Science and ''Rats and Mice,'' Bobby Corrigan, Handbook of Pest Control
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