Prof. Rob van Hees MSc
- building materials
- cultural heritage
Historic building exteriors suffer from weathering, city premises are graffiti targets, and algae are everywhere. Treatment is a must, as long as the cure is not worse than the disease. While water-repellents can stop rainwater and dissolved aggressive substances penetrating an external wall, drying a treated wall can pose problems. TNO advises on finding the right balance in external wall treatment - with no unwanted side effects.
Water-repellents can protect stony materials against rain penetration and damage. Treatment with water-repellents can also help eliminate wet patches and soiling of walls, and sometimes algal growth. A wall treated with a water-repellent is less prone to damage of this kind.
A precautionary antigraffiti coating will make it easier to remove graffiti from an external wall, and save the building owner money. However, any wall treatment carries risks, such as an unexpected change of colour or sheen. And, like water-repellents, antigraffiti coatings can make it hard for constructions to dry. The wrong treatment can even cause irreparable damage. A well thought-out approach is important, and indeed vital where historic buildings are concerned. With preliminary studies, risk evaluations, effectiveness assessments and recommendations for products and application methods, TNO helps building managers choose the right wall treatment.