Can brick masonry walls be used for foundation or basement walls? Should these walls be coated?
Although not commonly used for this purpose, brick masonry can be used for foundation or basement walls, but it should be covered with a waterproof or dampproof coating to prevent groundwater penetration and rising damp. This coating should extend above finished grade. It is also important to use a through-wall flashing at the base of the wall above grade so that water penetrating the walls above grade will not enter the top of the foundation walls. Preferably, this flashing should lap over the top of the waterproof or dampproof coating. The Brick Industry Association (BIA), in Technical Notes on Brick Construction 8B and 11E, recommends that Type M mortar be used in brick masonry in contact with earth, such as foundations and retaining walls.
The surface of the walls should be covered with a waterproof membrane or a dampproof coating to help prevent ground water from penetrating the masonry walls. In the past, BIA had provided some guidance in Technical Notes on Brick Construction 7 (from July 1961). This technical note stated that "where soil conditions do not permit a buildup of water, dampproofing the exterior face may be all that is required." These dampproofing procedures included applying one or two coats of cement mortar parging. Where water buildup is a problem, the note recommended applying a continuous bituminous membrane consisting of three or more alternating layers of hot bitumen and cotton fabric or felt. Extra protection against abrasion or puncture could be provided with a coat of mortar over the waterproofing. A gravel fill should be used against the dampproofing or bituminous membranes to permit free drainage of water to the drain tile. When the Technical Note 7 series was reissued in 1985, this information was no longer included.
It is much more common to use concrete masonry for foundations or basement walls. The National Concrete Masonry Association (NCMA), in TEK 3-11 and TEK 19-3A, provides many recommendations that are appropriate for clay masonry as well. Building codes typically require basement walls be dampproofed where hydrostatic pressure will not occur and be waterproofed where hydrostatic pressure may exist. Hydrostatic pressure may exist due to a high water table or poorly draining backfill.
NCMA TEK 3-11 states that draining water away from basement walls significantly reduces the possibility of water infiltration into the basement if the waterproofing system fails. It recommends using perforated pipe or drain tiles to facilitate drainage. Drainage and waterproofing systems should be thoroughly inspected before backfilling.
NCMA TEK 19-3A discusses several types of dampproofing and waterproofing coatings. Trowelling or brushing cement-based coatings onto masonry walls or applying a parge coat can be effective dampproofing methods. Rubberized-asphalt sheet membranes or liquid rubberized coating systems can provide a continuous barrier to water.
The sheet membranes have a polyethylene sheet on the exterior face. The rubberized asphalt serves as the adhesive and waterproofing material. These systems can bridge small cracks and voids. Many elastomeric liquid coatings and sheet membranes can also be effective. Sheet membranes are attached with adhesives, and the liquid coatings can be applied by airless spray, roller, or brush. Bentonite panels are another common way to waterproof masonry walls below grade. These panels use dry bentonite encased in kraft paper, fabric, or cardboard. After installation and backfilling, the bentonite will swell when exposed to water. Bentonite will expand to several times its original size. As it swells, it will fill and seal any cracks or voids in the foundation walls, joints between the panels, or small punctures in the panels. It is essential that the bentonite panels are protected from moisture until after installation and backfilling are completed.