Issues · 7 min read
Cracked roof tiles after moss removal — what went wrong and how to avoid it
If tiles cracked after a moss clean, someone almost certainly pressure washed a roof that should have been soft washed. Full guide to remediation and prevention.
The usual cause
In 12 years surveying Cobham roofs we have never once seen cracking caused by a low-pressure soft wash. Every case has involved either a domestic pressure washer, an under-insured contractor cutting corners, or an aggressive metal-blade scraper on brittle clay tile.
What to check for
Hairline cracks on the tile nose, missing granules in the tile field, chipped ridge tiles, or a lifted verge — all classic pressure-wash damage. A drone survey identifies these within a single flight.
Remediation
Individual tile replacement is straightforward while the roof is still under scaffold or ladder access. On concrete tile roofs older than 20 years a breathable polymer coating can restore the lost surface layer for a further 8–10 years without a full re-roof.
How to avoid it
Insist on written confirmation of a soft-wash-only method, a £5m public liability certificate, PASMA training records, and a 12-month no-moss guarantee. Any Cobham contractor unwilling to provide all four should not be on your roof.
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