Inspection

• Porches that show no signs of disrepair are good candidates for pressure washing. However, pressure washing could cause irreparable damage to bricks in poor condition. Moisture can seep behind the brick facade, causing mold or structural rot. A telltale sign of past moisture damage is efflorescence, which is a white, powdery residue on the brick. If the surface is worn but otherwise sound, choose a gentler method, such as scrubbing with a mild detergent solution and a soft brush and rinsing with a garden hose. Replace broken bricks and crumbling mortar before cleaning with any method.
  
  

Pressure Washer Choice

• Pressure washers are available from 50 to 5,000 pounds per square inch (PSI), or level of pressure the machine uses to force the water through the nozzle. Too much pressure can permanently scar the brick, remove mortar and force water behind the porch wall or floor, explains expert Tim Carter of Ask the Builder. Home models are usually less powerful. If you rent a professional pressure washer, use a low pressure setting. The right pressure washer nozzle is also important. A thin stream of pressurized water can cut grooves into the brick. Choose a nozzle with a wide, flat spray instead.
  
  

Cleaning Solutions

• Some stains may require cleaning solutions. However, solutions are often unnecessary and must be rinsed, so you will spray the porch twice. A conservative approach for applying chemicals with a pressure washer is to spray at the lowest pressure setting possible, such as 50 PSI, to prevent the solution from penetrating too deeply into the brick. Cleaning with a pressure washer is different from cleaning with solvents that break down stains. Pressurized water is a tool that removes grime by forcing it out of crevices rather than dissolving it like cleaners do.
  
  

Spray Method

• If your porch has a brick wall and a brick floor, clean the walls first. Holding the wand at an angle instead of pointing it straight at the brick helps prevent damage. Work slowly across the brick, cleaning the top row and working down the wall. Begin cleaning the porch floor at the farthest point from where the water will drain or be rinsed away. If there is a great deal of grime, occasionally rinse it off the porch to keep the mess under control.
  
  

Safety

• Pressure washers are power tools that can cause serious injury. Always wear eye protection to guard against flying mortar or brick particles and chemical spray. Never point the nozzle at skin or clothing. Pressurized water can quickly cut, abrade and bruise skin, and it can cause permanent eye damage.