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Cleaning historic buildings
14 Sep

Cleaning the Exterior of Historic Buildings

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  • Tony Williams

Historic buildings have their own unique requirements when it comes to cleaning their exteriors. These beautiful gems have been around for a long time, and they are revered by many. Their exterior surfaces may have weathered many storms, but that doesn’t mean that they don’t need occasional cleaning to protect them and make them look their best.
Can you power wash the exterior facades of historic buildings?

Historic buildings may be residential properties like homes, inns or bed and breakfasts, or commercial buildings like government monuments, banks, or museums. Whatever the type of building, power washing is possible and even recommended. If these properties’ exteriors are never kept up, it will undoubtedly create more costly repairs in the future. Mold and mildew are real issues for older buildings. They must be removed not only for esthetics but for the health and longevity of the property.

However, there are some rules to follow when caring for these types of buildings.


  • The use of chemicals is acceptable, but they must be non-abrasive. Eco-friendly chemicals are the best choice.
  • Know what chemicals react to surfaces such as marble, copper, bronze, or brick.
  • Use less pressure to be gentler on the surfaces. Using low-pressure water is a means of softening the dirt, mold, and mildew and will allow the unwanted deposits to come to the surface. Once all dirt is loose, it can be easily removed with low-pressure washing.
  • Choose soft bristle brushes if you need to clean difficult to reach areas instead of shooting water into space that could later cause cracking or other issues.


  • Don’t use abrasives if at all possible.
  • Don’t use sandblasting of any kind.
  • Avoid the use of wire brushes.

What if someone has defaced a historic building with graffiti?

As with all graffiti, you must first remove the paint with some sort of chemical cleaner that will loosen or dissolve the paint or stains and be combined with water or steam. You may need to use a soft, natural bristle brush to work with the chemicals on brick or masonry. This can be a challenging process, and repainting may need to happen.

Each kind of masonry is made of a unique composition, so you will need to understand how they might react to different chemicals. You must be careful so as not to create new stains or discoloration. If chemicals are required, testing on a small area first is imperative. Choose a spot that is not too noticeable in case issues occur. The weather may also affect the chemical reaction.

Can cleaning damage historic buildings?

Improper cleaning techniques can cause significant damage to the exterior surfaces of historic buildings. This is why hiring a team of professionals who understand how to clean historic masonry, tile, concrete, brick, stone, and other surfaces that have survived many years of the harsh elements. These buildings are important and must be carefully preserved for future generations.

When and why these buildings need to be cleaned must be considered. Suppose the building’s appearance is severely compromised and is now unattractive due to dirt, stains, soot, smoke, or graffiti. In that case, it is probably time to call in professionals who can clean the exterior and get it back to its former beauty. Removing harmful mold and mildew is serious and must be addressed for the future health of the building.

Knowing about previous cleaning issues is essential.

There should be records kept of previous cleanings of a historic property. Discoloration may not be caused by dirt but could be remnants of a water-repellent coating that causes stains of streaks. If that is the case, finding the right cleaning agent may take some doing and more than one cleaning. Cleaning agents can cause more damage than good and can sometimes cause adverse effects on other materials. In other words, what works for masonry or stone, may cause issues with wood or glass. It’s important to understand what chemicals work with what substance. Again, we can’t stress enough that cleaning this type of building should not be left to amateurs or by the owner or building staff if they are not familiar with all the products and issues they can cause. It’s not as simple as buying a pressure washer from a big box store for DIY projects.

If you own or manage a historic building in or around the Houston, Texas area, reach out to us at Goldstone Exterior. We would love to discuss making your property something to be proud of.

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