This section refers to comprehensive masonry cleaning and not simply removing excess mortar from the joint ledge. Cleaning masonry may consist of new construction cleaning or cleaning existing veneer. When cleaning masonry with a chemical or claening agent, a washing brush or pressure washer at a low setting (50psi or lower) should be used. It is always good to clean a test panel of the wall (in a hidden area of the exterior) to see how the product will react will the masonry surface to be cleaned. It is not recommended to sand blast or use Muriatic acid to clean masonry, they can both etch, streak, and burn/scar the masonry. A proprietary cleaner should be used by a reputable company with good technical support. These cleaners have special ingredients that increase the amount of time the products are effective and will not ‘dry in’ (dwell time) which tend to make them effective over a big area, when compared to raw acids.
Using pressurized water above 50psi will introduce the risk of driving the cleaner into the brick or block, which can cause stains and residue. This problem is further exacerbated by not pre-wetting the surface before using cleaning agents. Once thoroughly cleaned, rinsing will commonly consist of a minimum 400psi pressure wash at at about 4 to 6 gallons per minute. Cleaning should always be done when air temperatures are above 40 degrees and will stay that way during the washing/drying period. In colder weather, always use hot water (approx 160 degrees) when prewetting and rinsing. This will keep the cleaning chemical reactions from slowing down and will raise the surface temperature of the masonry.