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Stone is often thought to be timeless. Underground in the conditions of heat and pressure that created it, stone survives for millions of years. Brought to the surface, it comes under attack from the elements and therefore needs to be protected and maintained, instead of being assumed to last forever.
Nevertheless, there is a potential conflict between whether any adhering dirt or weathered veneer is in equilibrium with the environment and should not be upset, and whether the build-up of dirt that may lead to the breakdown of the stone should be prevented. It would appear however that much of the negativity surrounding the cleaning of natural stone façades is the result of poor research and improper selection of cleaning techniques. If cleaning is undertaken too late or not at all, the stone may suffer irreversible damage.
Why clean façades?
The primary concern is to prevent dirt build-up, principally from airborne particulates which may contain a range of potentially problematic materials that can react with the stone and reduce its lifespan. Damp areas are particularly likely to attract dirt – especially in a wet climate – and, if not already apparent, can be identified as a result of a clean. Thick layers of grime can retain water against or within masonry, resulting in increased salt cycling and accelerated deterioration in the stonework.
The removal of a seedling, for example, may prevent later damage from tree root growth and considerable disturbance to masonry, while dirt and staining may obscure evidence of structural failures that could eventually lead to significant shortcomings, such as stone falling onto adjacent public walkways.
Regular cleaning will help to identify areas where there is above average build-up of dirt and salts that may be indicative of more far-reaching problems which, if rectified at an early stage, may have considerable cost-benefit in the longer term.
The key to cleaning natural stone façades is a combination of minimum impact with great care and attention. Advances in understanding stone cleaning technologies, along with increased ease of access, have meant there are now generally far fewer issues arising from the range of available cleaning techniques. Building owners should, therefore, consider regular cleaning maintenance, rather than leaving their façades to the lottery of the elements.
The successful cleaning of any building façade depends on a unified team approach in which owner, architect, specialist technical advisor and contractor are all collaborating towards the objective of the safe and attractive cleaning of the building’s surfaces.
This technical information guide has been developed to provide you with more details about the range of restorative processes on the market and the benefits that a dry, non-abrasive façade cleaning can offer, compared to traditional methods.
Download the guide now or contact Thomann-Hanry® to order a free printed copy.