To remove loose dirt on the brick exterior of a house, use a garden hose fitted with a spray nozzle or spray bottle filled with water to remove it. Eliminate any moss or lichen found on the brick exterior using a mixture of 1 cup of bleach to 1 gallon of water applied with a natural bristle or synthetic brush.
To prevent bleaching of the brick when removing moss, soak the area thoroughly with water first. This step prevents the brick from absorbing the bleach solution. Never use a wire brush to clean exterior brick because it can leave trace amounts of metal on the brick surface and cause rust. Also, be sure to rinse off any cleaning solutions with water before the brick dries.
To remove stubborn dirt, use a mixture of dish-washing detergent or laundry detergent and water applied with a brush. Sometimes, grease-removing household cleaners can remove stains on brick. To clean large areas of brick, use a pressure washer on the low or medium setting. Before beginning, be sure to examine the integrity of the exterior wall, because pressure washing can damage old or crumbling brick and mortar.
To remove paint, calcium carbonate, rust and chalk, chemical removal is the best possible option; however, due to the risk of brick discoloration, etching and other damage, only professionals should use these products and only after spot-checking the solution on the brick.