Stone is a stunning building material, when it's kept clean.

Brick and stone buildings are known for their striking exteriors that can look beautiful for centuries. Yet masonry is also vulnerable to discoloration and staining, particularly if it’s ignored or if it doesn’t receive the proper upkeep and maintenance. Everything from outdoor furniture to environmental pollutants to weather conditions can cause unsighlty color changes on the exteror’s surface. For many types of stains, the longer it sits on the stone or brick untreated the more difficult it can be to remove. Facility managers should incorporate routine visual inspections of the building’s exterior into their maintenance schedules in order to ensure that discoloration is swiftly addressed.

Water can be considered stone masonry’s No. 1 enemy. That’s because all stone is porous to some degree. So as water from rainfall, snow or runoff penetrates into the building wall, it can discolor the stone blocks. When different parts of an exterior wall or statue retain different amounts of moisture, that can be reflected as slightly different shades of color on the surface.

Stone discoloration can also happen when moisture from the grouting compound discolors the edge of the stone blocks or contamination carried up from the mortar bed shades the stone. If the mortar bed contains calcium hydroxide, for instance, it can react to become calcium carbonate and trigger a gray color on the surface. Many natural stone also contains iron compounds that, over time, can oxidize and turn the blocks a yellowish brown color.

“Discoloration can easily happen from surface elements.”

Yet time and water aren’t the only things that can cause these blocks to change color. Discoloration can also happen from surface elements. For instance, exterior pollutants, including smog, can leave a residue on the building’s exterior that’s visible even at a distance. Fallen leaves and kicked-up dirt along the base of a stone wall can dirty the masonry.

Biologic stains like moss, algae, lichens and mildew are especially common in damp and humid climates. For stone buildings located near the sea, efflorescence can be an especially large issue. Efflorescence is a white powder that appears on the surface of the stone when water evaporates off stone, leaving behind mineral salts.

Inorganic metal stains from objects that are stationed near stone masonry can be both common and somewhat difficult to remove. Cans, flower pots and metal furniture can make inorganic metal markings that appear orange or brown in color. Copper and brass items can turn masonry a muddy brown or green shade.

While brick can also fall victim to efflorescence, environmental pollutants and inorganic metal stains, there is some discoloration that is more common for brick masonry. Known as lime run, calcium carbonate deposits typically appear as white or gray areas that can be crusty or raised in formation. They’re more common around small holes or cracks in the masonry, which is another reason that routine visual checks are suggested to keep brick masonry in top shape.

Silicate deposits, sometimes called white scum, can create a white, irregular shading over the surface of the bricks. White scum can stem from improper cleaning of the brick’s surface.

“Cleaning with the wrong materials can make the discoloration worse.”

Brown or tan discoloration can sometimes be linked to manganese oxide. This happens when tan, brown and black bricks have their coloring agents slowly migrate to the surface. Manganese staining is the top reason that unbuffered hydrochloric acid shouldn’t be used to clean these colored bricks. Opt for a specialized cleaner instead and always be sure to test the efficacy and safety of a cleaning solution in a small area of the wall before applying any solution to the entire surface.

Whether you’re tasked with keeping brick or stone exteriors clean, keep in mind that proper cleaning masonry requires careful consideration of both cleaning materials and procedures. Mortar joints can also be discolored or stained for a variety of reasons, and using the wrong mortar during tuckpointing could leave an unsightly color variation as well. Whenever cleaning or repairing masonry, experience is key.

Trying to remedy a discolored stone or brick wall with the wrong materials can occasionally make the situation visibly worse. Reach out to professionals to make sure that the masonry’s integrity is maintained as its cleaned. The professional crew at Clean and Polish brings decades of experience in masonry cleaning and repair to every task, which means you can get peace of mind that the building exterior will be restored to its original beauty and integrity.