When plants get a foothold on built structures they can seriously damage the fabric of the building. But a company called ASI have been trialling a treatment intended to stop plants being able to get grow on buildings.

It is called Chem-Crete Pavix and works by waterproofing the fabric of a building so there is no moisture for plants to live on. It is specifically being marketed for use on ancient stone structures, as well as contemporary stone, brick and concrete buildings and other structures, because it will not alter the look or nature of the building fabric.

It is a spray-applied water-based application that works by growing three kinds of crystals in the pores of the building fabric. These seek out water in the pores and dry it out as well as preventing water entering, while shrinking back in dry periods to allow the fabric to \'breath\'. A side effect is that it also keeps masonry cleaner by preventing water-borne dirt from entering.

Chem-Crete Pavix was developed three years ago in the USA and is now being tried out by London Underground on the arches of Putney Bridge Viaduct, which is brick and suffers from buddleia growing on it.

Chem-Crete Pavix costs about £4 a square metre to apply. If it works, London Underground plan to spray a lot more of their structures with it to cut down their annual bill for removing plants.

ASI like the product to be used properly and train and licence companies as applicators. For more information call ASI on Tel: 01908 373322 or talk to Ted Jenkins on Tel: 07739 418883.