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How much does it cost to clean a flat roof?
Our felt flat roof has gone quite green with moss and algae. What should I expect when getting quotes?
Expert Trade Answers
"You can't really clean a flat roof.
Depending on what finish it has... .does it have stone chippings, mineral felt, solar reflective paint?
If you would like more advice, please do not hesitate to contact me.
Kind regards
Pete"
Depending on what finish it has... .does it have stone chippings, mineral felt, solar reflective paint?
If you would like more advice, please do not hesitate to contact me.
Kind regards
Pete"
Answered on 27th May 2026 - Member since Dec 2025 -
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"Hi,
For a felt flat roof with moss or algae growth, the price can vary depending on the size of the roof, access, how much build-up there is, and whether it is just being cleared or treated afterwards.
As a rough guide, a small flat roof such as a garage, porch or extension may commonly fall somewhere around £250–£600, but it can be more if access is difficult, the roof is large, or there are drainage/gutter issues to clear at the same time.
With felt flat roofs, I would be careful with aggressive pressure washing. The roof should ideally be inspected first to make sure the felt, laps, edges, outlets and trims are still in sound condition. Moss and algae can often be removed carefully by hand or with a suitable soft-cleaning method, but if the felt is old, brittle, blistered or lifting, cleaning may reveal that repairs or replacement are actually needed.
When getting quotes, ask what is included, such as safe access, moss/debris removal, clearing outlets or gutters, waste removal, and whether any treatment is being applied to slow regrowth. Also make sure the contractor checks the condition of the roof before cleaning, as cleaning alone will not fix worn or failing felt.
Kind regards,
Jimmy James
Revived Roofing"
For a felt flat roof with moss or algae growth, the price can vary depending on the size of the roof, access, how much build-up there is, and whether it is just being cleared or treated afterwards.
As a rough guide, a small flat roof such as a garage, porch or extension may commonly fall somewhere around £250–£600, but it can be more if access is difficult, the roof is large, or there are drainage/gutter issues to clear at the same time.
With felt flat roofs, I would be careful with aggressive pressure washing. The roof should ideally be inspected first to make sure the felt, laps, edges, outlets and trims are still in sound condition. Moss and algae can often be removed carefully by hand or with a suitable soft-cleaning method, but if the felt is old, brittle, blistered or lifting, cleaning may reveal that repairs or replacement are actually needed.
When getting quotes, ask what is included, such as safe access, moss/debris removal, clearing outlets or gutters, waste removal, and whether any treatment is being applied to slow regrowth. Also make sure the contractor checks the condition of the roof before cleaning, as cleaning alone will not fix worn or failing felt.
Kind regards,
Jimmy James
Revived Roofing"
Answered on 27th May 2026 - Member since Mar 2019 -
report
"Anything from £200- £600 if need scaffold. Cost include muck away but a fairly quick job tbh but make sure you felt someone who knows what there doing as remember your flat roof is waterproof and they can cause damage"
Answered on 27th May 2026 - Member since Mar 2026 -
report
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