Wednesday, November 07, 2007

Weep Holes for Rodent Prevention


As we enter the fall season many pests will gain access to commercial and residential accounts via weep holes in the buildings of these accounts. Weep holes are either the gaps left between some bricks in external walls or the small openings in window framing. Weep holes serve two important purposes: 1) Ventilation of the internal wall cavity - without ventilation, mildew, dry rot and damp reduce the life of the internal wall studs and other building materials within the cavity, and 2) Drainage - water that enters the cavity due to capillary action, condensation, damage, or accidental flooding needs to escape somewhere.

Though necessary, unfortunately, weep holes also present a problem in that they also provide access to the wall cavity for rodents and insects, especially as temperatures cool down and pests seek harborage for warmth. Swarming bees and European wasps also love cavities. Field mice make a track through the weep holes looking for nest sites. Snakes, cockroaches and spiders find refuge in the cavity.

In desperation, many homeowners and commercial building occupants will resort to blocking weep holes with any number of materials such as silicon sealants, rolled up paper, plastic, scourer pads or steel wool to keep the pests out. These so-called solutions obstruct airflow to the cavity and set up moisture problems down the road. This can be very costly to fix later. The better way is to use small mesh screening inserts or weep hole inserts that can be purchased from your distributors or construction product distributors. These will keep the pests from entering in the first place. Applying a repellent residual first can also be useful for insect pests.

When thinking about pests that enter the weep holes, keep this rule of thumb in mind.1/2, ¼ and 1/16. Rats require a space only ½ of an inch wide to enter a building. Mice require a space of only ¼ of an inch wide to enter a building. And, most insect pests require only 1/16 of an inch wide space to enter a building. Weep holes come in various sizes, but can allow for most any of these pests. Excluding them with inserts or screening that allows the weep hole to still function as it should, while preventing the pests from entering is what is needed to properly keep pests out.
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