Retaining walls and other ground-draining structures all have weep holes. Weep holes offer a drainage outlet that enables any moisture that may enter the wall from behind through penetrating, capillary action, or leakage.
The installation of weep holes in brick masonry also acts as a ventilator, allowing air to reach the back of the wall to prevent the growth of mold, dry rot, and damp, all of which shorten the life and performance of the structure. In cavity walls, weep holes are often present in the exterior masonry. In cavity walls, you can also find them above windows and doors. They are offered at regular intervals to allow moisture to escape. Weep holes should be spaced apart by about 18 inches. Weep holes are used in engineering to release hydrostatic pressure, or water pressure, on walls. This decreases thickness and reinforcing requirements, hence lowering the structural design demand for the water and earth pressure. Weep holes also lessen the structure’s buoyancy and uplift, enabling the construction of lighter structures free from stability problems caused by uplift.
Weep holes can give pests like rodents and insects entry. Installing a baffled vent can solve this issue. I used a stainless steel weep hole cover when I built the wall.