Painting Exterior Brick
In most circumstances painting exterior brick is very basic and straight forward. These are the steps I take to paint exterior brick, whether it is unpainted or previously painted. Following these steps will make sure your paint job lasts.
Step #1 – Clean the Brick
I recommend using a pressure washer and about 1500 – 2000 psi. You don’t need a large unit or excessive pressure. The idea is to remove all the dust, dirt, spider webs, pollution and maybe some loose paint. To much pressure or holding the nozzle to close could damage the mortar.
If you have any efflorescence deposits, powdery residue, spend extra time rinsing with the pressure washer. Many washers can inject mild soaps into the pressurized water stream. This is especially useful for stubborn efflorescence deposits or other types of surface contamination.
Another method for removing difficult stains, especially oily stains, is to use a small amount of dissolved laundry detergent in water and a scrub brush. Producing a very clean surface is important when painting exterior brick. Any remaining residues could interfere with the primers ability to stick, compromising the entire paint job before it’s begun.
Step #2 – Remove Loose Paint and Repair Mortar
All loose paint must be removed and any repairs made prior to priming and painting brick. Any remaining loose paint could cause premature peeling. If you find any loose or peeling paint, use a hand scraper, stiff putty knife or wire brush to remove it. Areas of removed paint on the brick face can be sanded smooth for a better looking paint job. Use a circular sander or palm sander with 60 or 80 grit sandpaper.
Damaged or missing mortar can be repaired with premixed acrylic mortar patch available in a small tub or cartridge just like caulking. Or, you can use powdered mortar and mix it yourself, but it will need to dry for a few days before priming. The premixed mortar patch can be primed and painted immediately after it is dry.
Step #3 – Priming the Brick
All exposed brick or mortar must be primed with an acrylic masonry or quick drying universal primer. Primers like Zinsser’s 123 Acrylic primer are great for painting exterior brick. It will dry quickly, 1—2 hours to top coat, allowing you to paint sooner.
If your chosen primer is thick, add a splash of water to help with penetration. There is no need to prime the entire brick surface if the original paint is in good shape and is compatible with your finish paint.
All oil base paints must be fully primed if you plan on using an acrylic or latex over it. The rule is simple, oil base paint over water base paint but never water over oil without priming.
Step #4 – Caulking and Sealing
Gaps, cracks and holes larger than hairline, or 1/16 of an inch, should be caulked. This will keep water from entering the brick or mortar and getting under the paint.
Other areas that will need caulking are around windows, doors, and any wood trim to the brick. Generally, any gap that can let water in will need some kind of sealing. For extra large gaps use foam backer rod and polyurethane caulking. For all other gaps a good elastomeric caulking can be used.
Step #5 – Painting Exterior Brick
You can use any application method to paint brick. The main idea to remember is to make sure all cracks and pores are fully sealed. Any left open or unsealed could allow water to get behind the primer and/or paint; this will eventually lead to peeling.
No single application method will work perfectly alone. Painting brick usually requires a combination of different methods in order to adequately seal the brick.
Spraying: Typically, I spray the paint and back brush the first coat to make sure all areas have a good coat. For large walls a thick roller can be used to speed up the painting. The second coat can be just sprayed with back brushing or rolling.
Trying to get away without using a brush or roller is very difficult. When spraying you will need to apply the primer or paint using different angles. This always produces a build-up of paint on some areas and very little on others.
Brush and Roller: Brick can also be brushed and rolled. Use a thick roller, 3/4 – 1-1/4 inch depending on the brick and mortar. Don’t expect the roller to get into every nook and cranny; some brushing will still be needed.