Q: You’ve told us how to maintain our wooden decks, now please help those of us with brick patios. My uncovered brick patio is on the north side of a house built in the early 1930s. Although the slope of the patio is adequate for good drainage, the rain and fog and lack of sunlight mean that the brick is damp and shady much of the winter so that moss grows on many bricks.
Can you suggest a maintenance procedure to kill the moss or at least inhibit its growth?
A: Most often we recommend using a pressure washer to clean decks, patios and house siding. A pressure washer (either electric or gasoline-powered) converts water from your garden hose into a pressurized jet. The water may be adjusted from a pencil-like stream to a fanlike spray. Cleaning solvents can be mixed with the water to help with particularly tough jobs.
By far the best way to clean siding, clean a wooden deck or control moss on a brick patio is to blow the dirt and moss away with a pressure washer. Pressure washers may be purchased at all the large home centers for $1,500 to $2,500, depending on the model and pressure they generate.
For general household use, we’d recommend that you use a pressure washer capable of generating at least 1,500 pounds per square inch (psi) of pressure. Pressure washers are also available to rent at your local rental center. The cost is usually broken into two-hour, four-hour, daily and weekly rates.
Recently, our brother Bryan repainted Bill’s house in Boise. To prepare the exterior walls, he rented a pressure washer for four hours for $40.
Whether you decide to buy or rent a pressure washer will depend on how often you use it. A rule of thumb we use to determine whether to purchase or rent a tool is if the rental cost will equal the purchase price over a two-year period, we’d buy rather than rent.
Follow this procedure in cleaning your brick patio with a pressure washer. Start at an inconspicuous place on your patio. Hold the wand of the pressure washer a minimum of 10 to 12 inches away from the surface of the patio to prevent damage to the mortar joints.
Clean a small area at a lower pressure and a wide fan spray pattern. If you are not satisfied with the results, gradually increase the pressure and/or decrease the fan spray pattern until the surface cleans easily. Do not use any more pressure or any narrower fan pattern than is required to do the job. Be careful of the mortar joints. They are old and can be easily dislodged by a high-pressure stream of water.
If the patio is extremely dirty, and it sounds like yours is, use a commercial cleaning additive. These additives are available at home centers. Tell the salesperson what you are cleaning and they can recommend the proper cleaning agent.
After you do the initial cleaning, you may be able to get by without pressure washing for maintenance. Purchase a nozzle for your garden hose that will produce a narrow stream of water. Depending on the water pressure at your home you may be able to clean up the patio on a regular basis without going to the expense of either buying or renting a pressure washer.
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