Fungus
The Opportunist Black staining on exterior walls is often assumed to be dirt or pollution. In most cases, it is fungal growth. Unlike algae, fungus does not produce its own food. It depends on organic material to survive, which is why it is rarely the starting point. What is fungus Fungi are microorganisms that feed on […]
Algae — The Ringleader
Red and Green algae are in charge! When people notice staining on their walls, it is often the red colour that draws attention first. It stands out. It looks unusual. It raises concern. But red algae is only part of the picture. Green algae is just as important — and often more widespread. What is […]
The Usual Suspects:
What Is Really Growing on Your Walls Most people assume the staining on exterior walls is dirt, pollution, or general weathering. In reality, it is usually a living layer of biological growth. This layer is made up of four main organisms: Together, they form what is known as biomass growth. It starts with algae Algae […]
Exterior Treatment of Historic Buildings: What You Need to Know
Over recent weeks, we have explored the subject of exterior treatment from several perspectives: industry practice, material behaviour, biological growth and chemical selection. Taken together, these discussions point to a simple conclusion. Exterior treatment of historic buildings is not a routine cleaning task.It is a conservation intervention. This final article sets out the key considerations […]
What Does Responsible Exterior Treatment Look Like?
Over the course of this series, several themes have emerged. Exterior treatment remains a largely unregulated activity.Methods and materials vary significantly.The consequences of inappropriate intervention are not always immediately visible. The final question, therefore, is a constructive one. What does responsible exterior treatment actually look like? Understanding the material Historic buildings are composed of materials […]
Chemical Choice in Exterior Treatment: Why Transparency Matters
Choosing the right cleaning chemicals is vital to the long term health of the property
When Cleaning Causes Damage: Hidden Consequences for Historic Buildings
Exterior treatment is often judged by the immediate visual result. A façade that appears brighter or a roof that looks free from staining may be taken as evidence of a successful intervention. However, for historic buildings, the true impact of exterior treatment is rarely visible on the day the work is completed. Materials such as […]
Exterior Treatment and Professional Competence: Why Standards Matter
Exterior treatment work sits in a curious position within the built environment sector. On one hand, it involves direct intervention in historic and modern fabric — stone, lime render, slate, timber, lead, glazing and delicate architectural detail. On the other, it remains largely unregulated. There are no universally recognised competency thresholds, no mandatory accreditation […]