Roof Cleaning Specialists across the North West.

Moss on a roof is not just an aesthetic problem. Once it roots into the mortar joints at the ridge and the verge, it holds moisture against the bedding and accelerates freeze-thaw cracking. On a concrete tile roof in the wet conditions that run across most of Merseyside and north Cheshire from October to March, a heavy moss coverage can halve the service life of the mortar detail.

We clean using a low-pressure biocide application, not a pressure washer. High-pressure washing of an ageing tile dislodges the granule surface, strips the surface hardener, and can force water under the tiles at the battens. We do not do it. The biocide treatment kills the moss at the root and the dead growth washes clear over the following two to three months.

What the treatment involves

The biocide we apply is Andura Biocide Plus, which is approved for use on clay, concrete and fibre cement tiles and carries BBA assessment. It is applied by low-pressure soft-wash spray across the full roof surface, with a second application to the north-facing slopes where moss density is typically heaviest. We do not rinse the treatment off after application; the active agents need dwell time to work through the root structure.

Where the mortar bedding at the ridge is already failing, we include a re-bed and re-point of the ridge as part of the same scaffold visit. It makes no sense to clean a roof and leave open mortar joints that will admit water and allow the moss to re-establish from the joints upward.

When cleaning is and is not the answer

If the tiles are sound and the roof is structurally healthy but covered in lichen and moss, cleaning and treating is a good investment. It extends the roof life and is far cheaper than any tile replacement. If the tiles are porous, cracked or the deck is nearing end-of-life, cleaning cosmetically improves a roof that still needs replacing. We will tell you which situation you are in on the inspection visit.

What it costs

A biocide treatment on a standard three-bedroom semi including scaffold, two coats on north-facing slopes, and a re-bed and re-point of the ridge where needed typically runs between £650 and £1,100 plus VAT. Properties without need for scaffold access and with manageable ridge work run toward the lower end of that range. We quote after inspection.

What we back it with

The biocide treatment carries a 3-year guarantee against moss and lichen re-establishment where the treatment is applied correctly to a structurally sound roof. Any re-bedding and pointing work done on the same visit carries our standard 5-year workmanship guarantee. We do not guarantee results on porous or end-of-life tiles where the surface cannot hold the treatment.