Brick houses are good at keeping out the big bad wolf, but weeper holes are an Achilles heel when it comes to smaller pests. Weeper holes are gaps that are left between bricks to allow moisture that may accumulate in the air space behind the brick to escape. Most newer brick homes have these holes. They are usually found along the lower courses of bricks and also above windows, doors and small jut-outs. In industrial, commercial and institutional buildings plugs are usually placed in these holes during construction. In most residential construction, plugs are not put in the holes, probably as a cost saving measure. Without plugs, weeper holes can allow a variety of pests to enter into the structure of a house. These include: ants, cluster flies, lady beetles, paper wasps, yellow jackets, spiders and even mice if the holes are made too large. Even in larger buildings plugs are sometimes left out and we have treated office buildings and even hospitals that have serious problems with cluster flies and wasps entering through weeper holes.Small ants are able to crawl up the foundation and in through the lower weeper holes. Problems can also result from patios being built up against the foundation of the house and blocking the weeper holes. Sand is commonly used as the base material in patios and frequently becomes infested with ants. The ants are then able to move from their colonies in the sand through the weeper holes into the house without ever being noticed. If you are going to be building a patio or deck that will cover the weeper holes, you should plug them first with a material that will keep out pests but still allow moisture to escape.Cluster flies and lady beetles will enter through the holes that are higher up on the house and once in behind the brick are able to work their way inside. Yellow jackets will build their nest in the air space between the brick and the inner wall and sometimes chew right through the dry wall on the inside or come out through pot lights etc.
Plugs can be purchased at masonry supply stores and retrofit into the holes. However, some of the plugs will only keep out larger pests such as wasps and yellow jackets but not small ants. Other materials can be used, but care should be taken to ensure that moisture can still escape. Filter material such as that used for fish ponds would allow moisture to escape but would prevent even small ants from getting through. If you are having a new brick home built, you should ask to have plugs put into the weeper holes during construction.
Check your weeper holes occasionally over the summer and in the fall. It’s not just the big bad wolf that you want to keep out.