The Effects of Acid on Buildings

Everything needs cleaning, how often will depend on the size and purpose of the item but what about cleaning buildings? You might not realise but buildings build up dirt and grime over time and like anything else, can have their appearance greatly improved with a clean. So, what makes a building dirty?

Ever since the Industrial Revolution, our town and city buildings have been subjected to the fallout from air pollution resulting in damage and degradation. Pollutants that fill the air, such as nitrogen oxides and sulphur dioxide, lead to the formation of acid rain. Caused by the burning of fuels such as coal and oil, they can have a big impact on the surface of buildings when left to build up over many years. Such emissions reached their peak in the 1960s and have since continued to decline. So, does this mean our buildings are now safe from further damage?

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Unfortunately, it seems that since levels of these pollutants have dropped, our ancient stone buildings are still showing signs of degradation. This is caused by the fact that all the excess sulphur created since the beginning of the Industrial Revolution has permanently changed the stone surface of buildings. As rain water washes away the layers that have been sulphated, the exposed limestone begins to dissolve.

Since the 1980s the government has been examining the effects of acid deposition on our buildings. An organisation called the Buildings Effect Review Group was established to provide advice about the damage of acid on important buildings. There are many atmospheric conditions that can make our buildings dirty and/or damaged. For more information on Masonry Cleaning Companies, visit

There are many types of material that are susceptible to acid damage, as in fact most materials are. There are some building materials that are more prone to damage than others though and these include, limestone, carbon-steel, zinc, marble, paint and plastics. On our ancient buildings, acid damage can present itself as carvings that have worn away over time and black crusts formed in sheltered parts of stonework. Any part of a structure that sits under acidic water is also more prone to corrosion, like pipes and foundations for example.

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There are two types of corrosion, wet and dry. Wet damage occurs when pollutants are spread high up into the atmosphere, reacting with water vapour to create diluted acid which then falls in the form of rain. The effects of this can be felt anywhere and are not necessarily just felt in urban areas. Dry deposition happens when gas and particles fall to earth near to where they were emitted. This causes direct damage in the form of Sulphur Dioxide.

The surface of stone will begin to deteriorate and next, a layer of black gypsum will form. The gypsum will eventually blister, fall off and remove even more exposed stone. Other damaging agents include sea water, sea spray, carbon dioxide and ozone. The damage seen on our buildings is not so prominent in modern constructions but is seen heavily in ancient monuments. Around the globe, examples can be seen at the Taj Mahal, Notre Dame, Westminster Abbey and the Colosseum.

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