Parging, also called pargeting, is a technique for covering exposed brick, concrete block and poured concrete walls with a more attractive, waterproof surface. Homeowners can make their own parging material from cement and sand or purchase commercially prepared mixes for an easier application. A good parging job protects basement walls, foundations and any other brick or concrete surface, plus it makes your home look better.
Clean all surfaces with a stiff brush and water to remove dust and other loose particles. Remove any paint or grease from the concrete surface, since this can prevent the parging material from sticking. If your concrete surface has paint you cannot remove or loose areas, cover the surface with diamond wire metal mesh to provide a sound surface for the parging. Thoroughly saturate the area with clean water to encourage adherence.
Parging mixes can vary significantly. Commercial mixes usually just require mixing with water, but homemade ones need a little more work. According to Fine Homebuilding Magazine's "Foundations and Concrete Work," one good mix includes one part Portland cement to half-part hydrated lime to three parts washed sand. Backwoods Home Magazine recommends a mix of about two parts sand to one part cement. Sift the sand through a screen before mixing it with the cement to remove clumps and large particles, then mix the ingredients with water to form a soft, trowelable mix.
Apply the base coat directly to a clean, moist wall. Keep the coat relatively thin to reduce dripping. Most base coats should be about 1/4-inch thick. Work from the bottom of the wall to the top, using a cement-finishing or plastering trowel. After applying the entire base coat, use an old broom or other tool to lightly score the surface. Allow the parging to dry overnight, or for up to 24 hours, before applying the second coat.
You may wish to mix a little more water into the parging material for the finishing coat, since this provides a smoother material. Dampen the previous day's parging to provide a good bond, then repeat the bottom-to-top application process. King Home Renovation and Repair Products recommends a topcoat of no more than 3/8-inch thickness. Trowel this coat smooth, and finish it with a wet sponge if desired. Allow the parging to dry over the course of 24 to 72 hours, misting periodically with water.