Behind the Brick
Between the brick and the back-up wall, there is a narrow air cavity through which moisture drains down to the ground. No brick is 100% waterproof, so this air cavity is vital to get rid of any moisture that seeps through the brick. In this way, the outer clay brick veneer protects the back-up wall.
Brick at Grade
Brick built on grade can result in the ingress of moisture, either from direct water run-off or the build up of snow. Excess moisture present in the brick during the freeze-thaw cycles can result in spalling of the brick. Building Codes and good building practice dictate that brickwork should be a minimum of 150mm (6â€ť) above grade. This requirement also applies to any level surface such as paving, patio decks or balconies. Furthermore, the ground should be contoured so that the water drains away from the wall.
Base flashing should be installed below the bottom course of masonry, to prevent the upward migration of moisture due to capillary action (rising damp)
Always slope the grade away from the building. The masonry wall assembly should begin no less than 150mm(6â€ť) above the grade line.
Grade should be measured from the top of the finished surface. This means that grade should be considered to be at the top of a wooden deck, a stair tread, a poured concrete balcony, or any sort of finished surface, be it paving brick, gravel, asphalt, or earth in a planting bed.
Where wooden decks are build adjoining clay brick walls, the deck timber should be set back a distance of 40mm (1-1/2â€™) from the wall, to allow for the drainage of the water away from the masonry.
Important details for window sills are:
- minimize the number of joints
- ensure minimum slope of 15 degrees to sill
- provide drip groove
- provide adequate flashing including end dams
- caulk all joins
The most fail-safe detail is to choose a stone, concrete or metal sill material that is tailored to the window opening and has a slope on top and a drip groove/lip on the under side.
The tooling and profile of a mortar joint has a significant effect on the ability of the masonry to resist moisture penetration.
Raked joints are popular, because they accentuate the aesthetics of the brick. However they are not recommended for exterior masonry work in the Canadian or Northern U.S. climates. Raked joints provide a ledge for moisture ingress and retention.
Concave tooled joints are recommended for all exterior masonry. Joints should be tooled when the mortar is thumbprint hard. The jointing tool should be larger than the joint with, i.e. use a 12 mm diameter tool for a 10mm joint width. The tooling process smoothens and compresses the joint to promote superior water repellency.