DOFF cleaning is a specialized steam cleaning method widely endorsed by Historic England and the National Trust for Grade II listed buildings because it is exceptionally gentle on delicate masonry.
Key Characteristics
Superheated Steam: The system heats water to 150°C at the nozzle, transforming it into a high-temperature vapor rather than a liquid jet.
Low Pressure: Unlike standard power washers, it operates at low pressure (approx. 3-5 liters per minute), which prevents surface erosion or "scarring" of aged brick and stone.
Chemical-Free: The process uses only water, avoiding harsh chemicals that could react with historic materials or leave harmful residues.
Applications for Listed BuildingsBiological Growth: Effectively kills and removes moss, algae, and fungi. The high heat sterilizes the surface, killing spores to delay regrowth without needing biocides.
Coating Removal: Safely lifts layers of modern paints, graffiti, bitumen, and wax without damaging the underlying historic substrate.
Pollution & Grime: Gently removes carbon deposits and urban soot, restoring the building's original color.
Benefits for ConservationBreathability: By removing non-breathable modern paints and biological "crusts," it helps the historic fabric breathe, reducing internal damp issues.
Rapid Drying: Because the volume of water is low and the temperature is high, the surface dries almost instantly, preventing water saturation in porous materials.
Preservation of Detail: It is precise enough to clean intricate stone carvings and cornices without rounding off sharp edges.
Note on Regulations: Before beginning work on a Grade II listed building, you should consult with your local Conservation Officer to confirm if Listed Building Consent is required for the specific cleaning project.um.
