Have you ever wondered what the ‘stuff’ is that often coats old buildings? Biological growth effects many historic buildings, ranging from tree roots to micro-organisms. Some are perfectly harmless but other forms can cause both internal and external damage to building walls. Some of this biological growth can be protected for reasons of bio-diversity, such as some ferns and lichens.
Trees can cause damage to buildings as a result of root action under walls, foundations and underground drains. Drainage systems can become blocked by leaves and chimneys and gutters can become blocked by moisture-seeking plants like Buddleia resulting in damaged masonry.
Ivy and other creeping plants are commonly found on monuments and buildings. Such growth can enter joints and cause displacement of bricks, mortar and stone. Upon removing the plant, staining is often left behind on the masonry. Ivy can also push guttering away from walls and the constant shading by the plant means moisture cannot effectively evaporate from wall surfaces. If some ivy is desired for decorative purposes, it’s important to reinstate it on a trellis so there’s an air gap between the plant and wall.
Lichens are a type of fungus combined with algae that have a certain aesthetic appeal on many monuments and buildings. The presence of lichens can, however, lead to a deterioration in copper and lead flashings and roofing materials. For a professional Masonry Cleaning Service, visit https://www.stonehealth.com/
Mosses are a further example of biological growth found on buildings that contribute to their visual appeal. However, the presence of moss on roofing tiles can lead to damage similar to that seen with frost-damage. Large areas of moss also prevent moisture evaporation which contributes to damp problems and blocks water drainage systems.
Fungi and mould feed on materials like timber, breaking down the cellulose and darkening the colour of the timber while dry rot sets in. Mould produces spores that can be harmful to health, particularly for those with existing respiratory problems. Slime moulds are another micro-organism that can cause problems on masonry.
Bacteria are also found on buildings, especially in areas where there is water. Biofilms can form over masonry which can be removed by drying out the area and disposing of the surface growth.
Whilst we are used to seeing historic buildings with such growth that adds to their character and charm, some species cause indirect and direct harm to construction materials and methods. With some historic monuments, legal protection might prevent or severely restrict any removal attempts. Preventative methods are preferable, involving clearing water disposal systems and proactive pruning.