Even the most diligent homeowner rarely considers the need to clean older brick surfaces -- brick, after all, seems just about permanent. But cleaning bricks enhances their appearance and add to their longevity and preservation.

Walls encrusted with years of dirt and grime are subject to masonry decay at a far more rapid rate than clean walls. The discoloration and surface grime accumulation on brick occurs over a period of many years, so a homeowner is often unaware of how substantially the appearance of a brick wall has been impacted.

The major cause of masonry decay is moisture. A wall that is heavily painted or coated with surface dirt does not allow the natural evaporation of moisture contained within the masonry. Some hygroscopic staining materials may actually add moisture by drawing it from the surrounding atmosphere. Stained surfaces allow more surface area to be exposed to damaging atmospheric and other pollutants and may actually react with gases in the air to form corrosive materials which may dissolve or wash away acid-soluble cementing binders.

The three basic methods for cleaning brick surfaces are abrasive cleaning, power washing, and chemical cleaning.

Abrasive Cleaning

The use of abrasive cleaning methods (sandblasting, grinding wheels, and grit blasting) should be avoided completely in most circumstances. These methods are very effective in removing stains and dirt -- but they are also effective is removing too much of the brick's outer surface. For common solid core bricks (mostly pre-WWII), removal of the denser outer surface can result in long-term catastrophic spalling of the brick.

Power Washing

Over the past decade, the availability of smaller, lighter power washers -- including homeowner models -- has made this a common method. In many instances, power washing with water alone is a good option, but many homeowner model power washers lack sufficient pressure to really clean an older brick wall and many professional models have variable pressure setting which when set too high can be as disadvantageous as abrasive cleaning methods.

The high pressures can also cause moisture intrusion to the interior components of the dwelling, if used improperly. Be leery of the power washing contractor with 5000 pounds of equipment, and a quarter once of experience!

Chemical Cleaning

The most effective method for brick cleaning is chemical cleaning which typically combines the usage of various chemicals with a water rinsing or water power washing method. The chemicals dissolve the dirt or stains and the water rinses them away.

There are many different types of chemicals available and the determination of which to use must be made carefully by the contractor. Many of the chemicals historically used in masonry restoration are no longer suitable for a situation where the rinsate (the spent water/chemical solution) is allowed to run-off uncollected.

The chemicals generally fall into three categories: acidic (such as hydrofluoric or muriatic acid solutions), alkaline (sodium hydroxide and others), and organic (solvents, such as benzene). Some of these chemicals can be quite dangerous so appropriate training and care are required.

Except for a mild water wash with a homeowner type power washer, cleaning of masonry walls should not be attempted by the homeowner. It can be a very complex job that requires extensive knowledge of the materials to be used for cleaning, as well as the makeup of the material to be cleaned. Like so many other maintenance tasks, masonry cleaning is easy to do -- but difficult to do well.

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Published: February 16, 2001

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Andrew Kleeman is the National General Manager for Commercial Real Estate Services with U.S. Inspect, a nationwide inspection service with more than 100 engineers, architects, and inspectors on staff. He is an accredited property inspector in Pennsylvania and certified to perform asbestos and radon inspections by the Environmental Protection Agency. He has taught classes in Residential Construction and Design, and Environmental Due Diligence at Temple University, and he has also taught before the Pennsylvania Bar Institute.