Weep holes are small gaps or openings intentionally left in the lower courses of brick or masonry veneer walls to allow moisture that collects within the wall cavity to drain to the outside. They are a critical component of a properly functioning building envelope drainage system. However, these same openings can provide an entry pathway for termites, rodents, snakes, spiders, and other pests, making them a focal point during both building and pest inspections.
Purpose and Function
In cavity wall construction, the outer masonry skin and the inner structural wall are separated by an air gap. Water that penetrates the outer skin, whether from rain, condensation, or capillary action, drains down within this cavity and exits through weep holes at the base of the wall. Without functioning weep holes, moisture can become trapped, leading to damp, mold, efflorescence, and deterioration of internal wall framing. Weep holes are typically spaced at regular intervals, commonly every second or third perpend joint.
Pest Entry Risk
While essential for drainage, weep holes are among the most common unprotected entry points for pests. Termites can build shelter tubes through weep holes directly into the wall cavity, gaining undetected access to structural timbers. Rodents, particularly mice, can squeeze through surprisingly small openings. During a termite inspection, the inspector examines weep holes for evidence of shelter tubes, webbing, or blockage.
Weep Hole Protection
Pest exclusion products such as stainless steel mesh inserts, purpose-designed weep hole screens, and physical termite barriers can be installed to prevent pest entry while maintaining drainage function. These products must not impede water flow or they will defeat the weep hole's primary purpose.
Inspection Considerations
During inspections, blocked, rendered-over, or below-ground weep holes should be noted as defects. Inspectors also check that landscaping, mulch, or soil is not piled above the weep hole line, which can bridge termite management systems.