By: Adam McManus

Age and weathering impact buildings. Not only does the physical structure require lifecycle repairs, but the facades should also be cleaned and restored if facade restoration is required. Not long after initial construction, the facades of structures lose the gleam, color and finer details of their original appearance. Sunlight impacts manmade and organic materials. Ultraviolet rays cause colors to fade and molecular materials to break down. Façade details are often masked by staining and soiling of material surfaces, especially lighter colored façade features. Pollutants, vegetative growth and chemicals and particulates in water run-off can contribute to a soiled appearance, or much worse, material breakdown. A recent project at the U.S. capitol included repairs and comprehensive cleaning of the building envelope.

Both geography and climate impact façade systems. Sand and dust storms blow through metropolitan areas that are surrounded by deserts. Sand is an abrasive that can erode the face and finish of the surfaces over time. Stone can lose definition and polish, coatings can lose reflectivity and brilliance, wood can lose coating and definition, and glass can be etched. In colder climates, freeze thaw cycles are problematic. Ice buildup often forms and breaks off. Gravity pulls heavy masses onto ledges, canopies and other façade features, thus damaging the surfaces. Persistent or heavy rainfall can impact masonry work by saturating brick and mortar joints. Saturated façade elements that do not drain well can result in efflorescence and calcium carbonate buildup that stain facades white.

Chemical pollutants in the atmosphere also react with façade surfaces. Coatings, stone and other bare surfaces may be susceptible to chemical attack. Limestone is a soft calcium-based material; acid rain can erode this soluble stone. Due to atmospheric pollutants, large metropolises are often more affected by acid rain.

Along beaches and similar geographic areas, the effects of soluble salts from the ocean react with materials such as steel, iron and aluminum. Corrosion of metals in humid climates is accelerated in saltwater environments. Regular cleaning of the salt covered surfaces is helpful in reducing the effects of salty atmospheres. It’s prudent to apply protective coatings that can withstand a high concentration of humidity with the presence of atmospheric salts.

The presence of organic life such as vegetative growth, mildew, algae and climbing ivy can be quite destructive to certain types of stone, wood and masonry systems. Roots or tendrils can invade the crevices in mortar and stone. This allows moisture to infiltrate those areas and break down wood, soft stone or mortar composition. Regular removal of plants and vegetative build-up from wood and some stone surfaces will help elongate the lifespan of the façade. Newer technologies such as lasers are currently being employed. The Cloisters Museum in New York used laser cleaning method to remove atmospheric particulates and organic material. Bird excrement often stains and soils surfaces. It’s important to utilize the appropriate safety equipment during removal of excrement to avoid harmful airborne diseases that can impact the respiratory system.Concrete is often stained by iron oxide from corrosion run-off, battery acid, carbon black, soap scum, metallic discoloration, as well as other organic matter. Each type of stain warrants a different approach for removal from and restoration of the existing surfaces.

In order to avoid damaging the composition and other complimentary protective systems, material surfaces at building facades should be treated with appropriate cleaning solutions. These might include lasers, light detergents, poultices with chemical peels, low pressure water misting and high-pressure water systems. The International Masonry Institute references many types of cleaning methodologies that can be employed. Periodically cleaning surfaces can help preserve the finishes and reduce the cost of much more substantial cleaning after longer periods of deferred maintenance. Certain staining may be a symptom of a poorly designed façade system that requires replacement, or repairs beyond superficial cleaning methods.

Choosing the appropriate agents and methodology to effectively clean façades and prevent further damage to material surfaces is imperative, particularly on large scale buildings. A qualified building exterior specialist with expertise in all types of material science and cleaning technologies is a great resource to assist in façade related evaluations and specifications for proven solutions. Whether it’s a project as grand in scale and complexity as the U.S. Capitol or a smaller building of architectural significance, there are numerous benefits in cleaning a building’s façade system.

 

 

Sources:

h ttp://imiweb.org

https://www.metmuseum.org/blogs/in-season/2014/laser-cleaning-for-stone-conservation

h ttps://www.flickr.com/photos/uscapitol/25976321513/in/album-72157667034007082/

https://www.aoc.gov/stone/capitol/project-overview

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