How To Properly Clean Masonry

The accumulation of pollutants, biological growth, or paints and coatings can be detrimental to the longevity of any masonry structure.  The cleaning of these surfaces should be considered regular maintenance.  However, this cleaning should be handled carefully, and by experienced personnel.  This includes selecting the appropriate cleaning method.

What Should Be Used To Clean Masonry?

Sandblasting is no longer considered an appropriate method for cleaning masonry.  Pressurized water and cleaning chemicals are the most commonly used methods, with water pressures regulated to prevent damage, and proprietary cleaners carefully selected for the specific application.  Chemical cleaner types are acids, alkalies and organic compounds. These can be applied as a liquid or poultice.  For best results, sample panels should be applied on inconspicuous places to determine the dilution ratios of cleaner to water.  

Should Acidic Cleaners Be Used On Masonry?

Acidic cleaners should be used only on non-acid sensitive masonry (unpolished granite, most sandstones, slate, unglazed brick, unglazed terra cotta, cast stone, and concrete). Alkaline cleaners should be used on acid sensitive stones (limestone, marble, calcareous sandstone, glazed brick, glazed terra cotta, and polished granite).

Preparing Masonry For Cleaning

In almost all cases the masonry surfaces should be prewet before applying any chemical cleaners.  For best results, the cleaner is typically scrubbed into the stained surface with a stiff bristled brush, allowed to dwell for a pre-determined time before rinsing with pressurized water.  The use of hot water is often advantageous for more difficult stains.  Warmer ambient temperatures will also provide better results, and cleaning should never be done when temperatures could potentially get close to freezing.  

Masonry Cleaning For Historic Buildings

Other cleaning methods include low pressure water soaking and various micro-abrasive methods.  These methods are more commonly used on historically significant structures where the mildest means possible is preferred.  

As always, the contractor selection process is critical for the success of any project.  At Mid-Continental Restoration we take pride in our 75 years of industry experience, and we train our crews to use the most proven methods in the industry.