Owning a listed building in London comes with clear responsibilities, especially when it comes to the exterior. Brickwork, stone facades, render, and decorative details all contribute to the building’s historic character, and even cleaning can fall under legal control.

If you’re considering professional exterior cleaning using non-abrasive machines such as DOFF or TORC, here’s what you need to know.

One of the biggest misconceptions is that DOFF (steam) cleaning is simply hot pressure washing.

In reality, the defining difference is pressure, not temperature.

Pressure washing relies on a powerful jet of water to remove dirt, moss, algae and stains. Whether the water is cold or heated, the cleaning power comes from the force of the water striking the surface.

A DOFF machine works differently. It produces superheated water at temperatures of up to 150°C, delivered at very low pressure. The high temperature breaks down dirt, organic growth, paint and biological contaminants, while the low pressure helps protect delicate materials from unnecessary damage.

This combination makes DOFF cleaning one of the safest and most effective methods for cleaning sensitive masonry and heritage buildings.

Regular exterior maintenance helps prevent costly repairs and keeps properties looking their best.

Routine cleaning such as window cleaning, gutter clearance, pressure washing and facade cleaning can protect surfaces, reduce long-term costs and prevent small issues from becoming bigger problems.

A proactive maintenance plan is a simple way to preserve the condition and value of a property.

Painted surfaces require careful cleaning to avoid damaging the finish underneath.

The right method depends on the type, age and condition of the paint, with options such as soft washing, low-pressure cleaning or specialist steam cleaning.

A test patch is recommended before larger works to ensure the safest and most effective cleaning approach.

London's architectural heritage is one of the city's greatest assets. From Georgian townhouses in Islington and Victorian terraces in Kensington to centuries-old churches, civic buildings, and listed landmarks throughout Westminster and the City, historic buildings tell the story of London's past. Preserving these structures requires specialist care, and when it comes to exterior cleaning, using the wrong method can cause irreversible damage.