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7 min read · Updated 2026-01-15

What Is Soft Washing a Roof?

Soft washing is a low-pressure roof cleaning method that uses a roof-safe biocide to kill moss, algae and lichen at source. It's the professional standard across the UK because it delivers results that last years without damaging the tile surface.

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Written by

JW

James Whitmore

Founder & Lead Roof Technician, Nottingham Roof Cleaning

James has spent 12 years cleaning, inspecting and restoring roofs across Nottinghamshire. Formally trained in soft-wash methodology, IPAF-certified for powered access, and a working member of the UK Roof Cleaning Association. He personally inspects the majority of jobs the company quotes.

  • SoftWash UK — Accredited Technician
  • IPAF (Powered Access) — Certified
  • PASMA (Mobile Scaffolds) — Certified
  • Environment Agency — Registered Waste Carrier
  • UKRCA — Member

Soft washing is a low-pressure roof cleaning method that uses a roof-safe biocide to kill moss, algae and lichen at source. It's the professional standard across the UK because it delivers results that last years without damaging the tile surface.

The mechanics

A 12-volt or air-driven pump applies biocide at under 500 psi — roughly the pressure of a strong garden hose. The chemistry does the cleaning work: the biocide penetrates moss and algae at the cellular level, killing organisms outright rather than blasting them off intact.

Killed growth loses its grip on the tile within 2–8 weeks and washes off in normal rainfall. The roof continues to improve visually for months after the initial treatment.

Why the low pressure matters

Concrete tiles have a factory-applied cementitious surface coating that acts as their primary weather barrier. High-pressure water strips that coating, exposing porous aggregate that holds moisture and grows moss back fast. Soft washing keeps the coating intact.

The biocide products

Professional soft-wash biocides are typically based on benzalkonium chloride at controlled dilution. They're roof-safe, breakdown to inert compounds within days, and don't damage nearby planting when applied correctly with appropriate sheeting.

How long the results last

A properly executed soft wash on a Nottingham roof typically stays visibly clean for 3–5 years. Fitting zinc or copper ridge strips at the same time can push that towards 7 years. Regular biocide top-ups extend it further.

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If you'd like a fixed-price quote for your Nottingham property, request a free roof inspection using the form on this page — we'll typically respond within one working day. Every quote is written, fully insured and includes gutter clearance as standard.

Technically reviewed

Sarah Alden MCIOB — Chartered Construction Manager — independent technical reviewer. Sarah is a Chartered member of the Chartered Institute of Building with 18 years in domestic roofing surveys. She independently reviews the technical accuracy of published content on this site.

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Frequently asked questions

How much does the work discussed in this guide typically cost in Nottingham?
For most Nottingham properties, a full soft wash with moss removal and biocide falls between £400 and £950. Biocide-only treatments start around £250. Restoration work with re-colouring is a separate service and starts around £1,600. We provide fixed written pricing after a free inspection.
What treatment schedule keeps moss under control in Nottinghamshire?
A full clean every 3–5 years is standard. Roofs under tree cover, on north-facing slopes, or in the wetter west of the county often benefit from a biocide top-up at 24 months to hold results between full cleans.
Should I choose soft wash or pressure washing?
Soft wash. Pressure washing damages the tile surface, voids many manufacturer warranties, and forces water into places it doesn't belong. Soft wash is slower but preserves roof life and delivers longer-lasting cleanliness — the only method we use on domestic tile and slate.
How long will results last on my Nottingham roof?
Expect 3–5 years of visibly clean tiles and up to 5–7 years of heavy-moss control with a mid-cycle biocide top-up. Regular gutter clearance and trimming overhanging branches extend results further.
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