From time to time, your Fishers Realtor ® is so busy with her buyers and sellers, she needs a ghost writer; let me introduce one of the inspectors I use and trust, Rob Rehm. Rob wrote this piece on Weep Holes and I think it is something my readers should understand. So, thank you Rob for your expertise on this article.
Have you ever seen holes or plastic tubes in the mortar joints just above the foundation and over windows and doors? Sometimes there is a small length of rope sticking out of the joint instead of a hole. Note– you aren™t seeing sloppy construction, the holes or piece of rope are supposed to be there. Don™t seal them up because they serve a valuable purpose.
While a masonry wall is the first line of defense against water penetration, it can leak. Masonry is porous and can absorb moisture in extreme weather conditions. Weep holes are the exit port for the drainage cavity behind the masonry wall. If the wall is built correctly, the weep holes allow moisture behind the masonry to exit. These holes also serve as pressure equalizers making it less likely that wind-driven rain will penetrate the wall.
The drainage cavity has five essential elements:
- The exterior wythe (the vertical section of a wall that is equal to the width of the masonry unit) of masonry provides the first resistance against moisture penetration
- An air space of at least one inch
- An interior wythe of masonry or other material such as frame wall
- Flashing at all interruptions in the drainage cavity such as at the base of the foundation and around the openings for such windows
- Weep holes at all flashing locations– recommended spacing of 33 inches.
For a cavity wall to function properly, water that collects on flashing must be able to drain through the weep holes to the exterior or the building. If weep holes do not function properly, water collecting in the cavity can infiltrate the building interior.
There are many homes built without weep holes that have or will likely never become a problem. However, good building practices and most building codes suggest weep holes should be installed when the home is built. Many code officials will look the other way or allow occupancy without the installation of weep holes.
Conversely, the absence of weep holes occasionally allows so much moisture to accumulate that metal fasteners turn to rust, wood-destroying insects are encouraged, or rot develops. It is unlikely that a visual home inspection will reveal these problems unless conditions are so severe that cracks in the walls or other indicators are visible. The most likely visual manifestation of a problem will be water stains, damp areas or rot at the foundation plate and/or floor band as well as stains or damp areas at the top of the foundation wall.
Weep holes can be added. However, most masonry experts question the effectiveness of retrofit without at least partial removal of the masonry, which is very expensive. Home inspections are not code compliance inspections. Professional home inspectors can look and determine if weep holes are present, however, they have no way to ensure absence of hidden moisture damage without invasive investigation. Therefore; it is our perspective that weep holes should be installed when they are missing on a property.