Roof cleaning removes moss, algae, lichen, and general soiling from roof tiles and slates, improving the appearance of the property and preventing the biological growth from lifting and dislodging tiles or retaining moisture that accelerates deterioration. Understanding the cost and the best cleaning method helps homeowners make an informed choice.

Why Roofs Need Cleaning

In the UK's damp climate, moss and algae establish on roof tiles particularly on north-facing slopes where the surface remains wet for longer. Established moss growth can lift tile edges, allowing water penetration, and the accumulated biomass retains moisture that contributes to freeze-thaw damage in clay and concrete tiles. Algae creates a green or black staining that is visible from the street. Lichen, the most tenacious organism, bonds to the tile surface and takes years to remove if not treated.

Cleaning Methods

Soft washing

Soft washing uses biodegradable biocidal treatments applied at low pressure to kill moss, algae, and lichen at the root. The dead growth is then rinsed away or left to weather off over several months. Soft washing is considered the most appropriate method for most tile types as it avoids the physical damage that high-pressure washing can cause to clay plain tiles, aged concrete tiles, and natural slate. It is also more effective at preventing regrowth as the biocide kills the organism rather than simply blasting off the visible surface growth.

Pressure washing

High-pressure washing physically removes surface growth by force. It is faster and produces an immediately dramatic result but can damage fragile or aged tile surfaces, dislodge mortar from ridges and verges, and may simply encourage faster regrowth without a biocidal treatment. Most professional roof cleaning specialists now recommend against aggressive pressure washing on older or more fragile tile types.

Typical Costs

For a standard three-bedroom semi-detached house with a roof area of around 60 to 80 square metres, professional roof cleaning using soft washing or biocidal treatment typically costs two hundred and fifty to five hundred pounds. Pressure washing of a similar area costs two hundred to four hundred pounds. Adding a post-clean sealant or guard treatment to inhibit regrowth adds one hundred to three hundred pounds.

After Cleaning

Following cleaning, a roof inspection may reveal tiles that have been dislodged by the growth, cracked tiles, or pointing that has been softened by the biocidal treatment. Addressing these maintenance issues at the same time as the cleaning visit, while scaffolding or access equipment is already in place, is more cost-effective than a separate return visit.

Summary

Professional roof cleaning costs two hundred and fifty to five hundred pounds for a typical three-bedroom house using soft washing. Pressure washing is slightly less expensive but less suitable for aged or fragile tiles. Soft washing with biocidal treatment provides longer-lasting results. Roof cleaning involves working at height and should be carried out by insured professionals rather than as a DIY task.