Most people know that the weather and pollution can have adverse effects on the environment; causing increased CO2 levels, rubbish found on beaches, oil spills, cliffs worn away to the point where they collapse. But did you know that the weather and pollution can also negatively affect buildings and structures?
What exactly is weathering and pollution?
Weathering is the process that occurs when a surface, usually rock, brick or stone, comes in to contact with the constantly changing elements of earth’s atmosphere. This contact often causes the surface to change in some way, and possibly become weaker and wear away. There are two classifications of weathering; physical and chemical. Physical weathering involves the breakdown of a surface through direct contact with atmospheric conditions, such as heat or ice etc. Chemical weathering involves the direct effect of biologically produced chemicals. Each type of weathering can take place at the same time, and one can even exacerbate the other.
Pollution is the introduction of substances and contaminants to the environment which can cause adverse affects. Pollution can come in many forms, but in regards to buildings and structures, air pollution and atmospheric pollution will be the types whose effects are most noticeable. Regular cleaning of the building facade with a water free poultice cleaner is recommended to preserve stone and masonry.
In Britain there is a huge variety of buildings and structures, each constructed from numerous different materials. Also, in Britain we can see a vast range of different weather conditions, spanning from hot and humid, to extremely cold and frosty, and most people are more than aware of the levels of pollution that currently exist in this country. The vast history of Britain means that a large number of important historical buildings are always especially vulnerable to this dramatic range of weather conditions, in addition to commercial and domestic properties.
What damage can they can cause?
The exterior material of a building, whether it is brick, limestone, concrete etc. will have a lot of impact on how much damage from weathering and pollution it can withstand. For example, a concrete exterior would be able to withstand a lot more elements than limestone, which is quite soft and susceptible to moisture.
We often see a lot of rain in Britain, especially in winter months, so it should come as no surprise that many building exteriors are at risk of water damage. The most debilitating effects from water damage are often caused when the exterior treatment/cladding/render has not been applied properly, leaving it sealed ineffectively, causing water to seep in to areas that it otherwise wouldn’t. Rain and water may also cause staining on a building façade, as it loosens dirt and debris from the roof or gutters, it will pull this down the building as it runs off, leaving unsightly stains when it is dry. These can become increasingly hard to eliminate the longer the stains are left to build up. In the winter months, water can also pose an extra risk for building exteriors, especially older buildings. Combined with wet weather, the freezing temperatures of winter can cause the surface water on a building façade to freeze, which means the volume of water will expand and then contract again when the ice melts. This frequent expanding and contracting of water on the surface, or in the cracks and crevices, of a building exterior can put stress on the material and can even cause cracks and weaknesses. In addition to these risks, water can also cause any steel exteriors to rust over time.
Pollution is a constant topic in world news, and rightly so, as each country aims to cut carbon emissions and increase the amount of waste that is recycled in order to improve the environment and extend the longevity of our natural resources. However, not many people realise that pollution can also directly affect the buildings and structures around us. At ground level, particularly in urban city areas, there will be a constant presence of smog and fumes in the air from the high number of cars and other vehicles that emit exhaust fumes, even if you can’t see them. These fumes can sometimes cause staining of building façades, particularly when the building is exposed to these fumes for long periods of time without proper cleaning and maintenance. Another aspect of pollution, which is not always immediately evident, is acid rain. Due to the production of sulphur dioxide, some rainfall will become overly acidic, which causes the gradual break down of the surface area of building façades. The presence of acid rain has declined in recent years, but certain materials, such as limestone, are far more susceptible to even extremely low acid concentration.