For proper drainage, cavity walls must be detailed cor- rectly and constructed to keep the cavity clear of mortar drop- pings and prevent weep hole blockage. Weep holes must be placed di- rectly above flashing and should be spaced about 16 to 24 inches o.c. maximum.
Spacing of wick and tube weeps is recommended at no more than 16” on center. Weep spacing is permitted by most building codes up to 33” on center. If other than an open head joint weep is used, be sure the weep is clear of all mortar to allow the wall to drain.
The Weep Vent should be spaced at no greater than 900mm centres to meet N.H.B.C guidelines, which state, “weep holes are recommended to be sited at every 450mm maximum with at least two per opening above all windows and doors.”
To allow water to drain out of the cavity, weepholes should be provided in the outer leaf immediately above the cavity tray and positioned at a maximum distance of 900mm centres. The tray should dress over any associated flashing or vertical membranes to ensure any water is drained outwards as illustrated in Diagram 3.
R703. 8.6Weepholes. Weepholes shall be provided in the outside wythe of masonry walls at a maximum spacing of 33 inches (838 mm) on center.
Weep holes are usually spaces every 4 to 4 feet. The weep hole size in retaining walls is usually 2 to 4 inches in diameter, depending on the type of soil used and the water volume. This can vary as finer soils like clay need larger weep holes, while coarser soils will need smaller ones.
Without masonry weep holes, or if the existing drainage system is blocked or broken, capillary action can result in the water becoming trapped inside the cavity wall.
weepholes should be provided at a maximum of 450mm intervals. each opening should have at least two weepholes. cavity trays or combined lintels should have stop ends.
As an alternative to weep holes, most new construction will connect the drainage zone to a perforated drainage pipe located behind the base of the wall outfalling to a manhole.
This gap acts as a protective barrier, preventing external moisture from reaching the internal leaf of the wall. It is suitable for buildings of any height. The primary purpose of the air space in a cavity wall is to act as a barrier against rainwater penetrating the inner face of the wall.
Manufacturers recommend installing them at an angle in the mortar of the head joints, spaced 16 inches apart. COTTON WICKS Cotton wicks are used to form another type of weep system. A 1/4 to 3/8 inch diameter rope is installed in joints at 16 inches on center.
Weep holes - Statutory Regulations
2 says "Weepholes shall be provided to drain moisture from or through masonry construction. Where flashings are incorporated in the masonry, weepholes shall be provided in the masonry course immediately above the flashing, at centres not exceeding 1200 mm."
Vents are required at 450mm intervals and each opening should have at least 2 weep holes.
It is difficult to add weep holes after the walls are constructed. If the weep holes are drilled, they will typically puncture the flashing. This is true even if a special guide is placed on the drill. If the hole does not go all the way through the mortar then it will be ineffective.
Even if you used the code as a basis of the requirement for weep holes, you would be surprised to learn that weep holes were nor mandated in the single family code until 1983 CABO, mandated by the 1985 Kentucky Building Code. Home inspectors are calling out missing weep holed on house built before 1985.
The BIA (Brick Industry Association) recommends that weepholes be spaced a maximum of 24", 16" when rope wicks are used, and that they be not less than ¼' in diameter.
Weep holes must be placed di- rectly above flashing and should be spaced about 16 to 24 inches o.c. maximum. The most common types of weep holes are open head joints, louvered vents, rope wicks, tubes, cellular vents, or a combination of these.
This research demonstrated that even under truly extraordinary conditions water rarely enters the weephole and even if it does it cannot be blown high enough up in the cavity to create internal damp problems. To understand why, it's important to look at the details of a correctly constructed cavity wall.
Weep holes shall be provided in the exterior wythe of masonry walls and shall be at a maximum spacing of 33 inches (838 mm) on center (o.c.). Weep holes shall not be less than 3/16 inch (4.8 mm) in diameter.
The inclusion of weep holes in new build homes is essential for several reasons: Moisture Control: Weep holes help manage moisture levels within the wall cavity, preventing water from pooling and causing damp patches or mould growth.
Weep holes are strategically placed openings that allow water to escape from behind the retaining wall. Key considerations include: Appropriate spacing: Often 1-2 meters (3-7 feet) horizontally, with vertical spacing determined by wall height.
Weep holes are often located at the bottom of brick exterior walls. They look like vertical gaps in the mortar joints between bricks. Because brick masonry is porous, water may penetrate the surface and get behind the wall.
As a general guide weep holes at floor level should be a minimum of 75mm above finished ground levels.
Problems With Weepholes
If weep holes are left unprotected in brick walls they provide access to the wall cavity for rodents and insects. Swarming bees and European Wasps love creating nests in cavities.
It's obvious that small pests such as cockroaches and spiders can crawl through weep holes, but vertebrate pests such as lizards, snakes and even mice can also squeeze through a normal weep hole.