Roof Cleaning

There is a widespread and expensive misunderstanding that a roof should be pressure washed clean. On concrete interlocking tiles the surface layer of cement and colour pigment is only a fraction of a millimetre thick. Blast it with a pressure lance and the moss comes off, along with the very surface that was protecting the tile — which is why some pressure-washed roofs green up worse than before within two or three years.

We do not pressure wash roofs at all, on any covering, at any pressure setting. Even on the lowest setting, pressure washing strips the protective surface from concrete tiles, forces water under the laps, and damages ridge and verge pointings. Instead we use a soft wash approach: physically remove the bulk of the moss by hand scraping, then apply a biocidal treatment and let the chemistry finish the job over the following weeks. It is less instantly dramatic on day one and considerably better for the roof, and the results last far longer.

Slate and clay are a different case again. Natural slate is brittle and delaminates, older clay tiles can be porous and frost-damaged, and both can be cracked simply by being walked on carelessly. On those roofs the work is almost entirely hand and treatment-based, with proper roof ladders spreading the load.

Water is the mechanism behind nearly all of it. A saturated moss layer keeps tiles permanently damp, and when that water freezes it expands, spalling the tile surface and opening up hairline cracks. Over years this shortens the working life of an otherwise sound roof covering considerably.

The more immediate problem is drainage. Loose moss travels: it slides down the pitch, gathers in valleys, drops into the gutter, and lodges in the outlet. Once the outlet is blocked, the gutter fills, overflows and runs down the fascia and wall. That is how you end up with damp patches on internal walls, rotten fascia boards and stained render, all traceable back to moss on the roof.

There is a weight consideration too. Dry moss is light; a saturated mat across a large roof plane is not, and on older or already-stressed structures that additional loading is worth taking seriously. Clearing it, and keeping it clear, is straightforward preventative maintenance rather than cosmetics.

Roof work is height work, and we treat it as such. Access is planned before the job, not improvised on the day: correctly footed ladders, roof ladders to spread load rather than walking directly on tiles, and scaffolding or a tower where the pitch, height or condition of the roof calls for it. We carry full public liability insurance and will confirm the details before starting.

Ground protection matters just as much. Moss coming off a roof arrives in volume, so drives, patios, planting and paths beneath the work are sheeted, and everything is collected, bagged and taken away rather than raked into a border. Gutters are re-checked and flushed at the end of the job, and downpipes are tested to make sure water is running away freely.

We will also flag anything we find while we are up there — slipped tiles, cracked ridge mortar, missing verge pointing, a failing flashing, a soil vent pipe collar that has perished. Small repairs we can usually deal with there and then; anything larger we will describe clearly with photographs so you can decide what to do.

A roof that is physically cleared and then properly treated with biocide will typically stay looking good for several years, far longer than a roof that has only been washed. North-facing pitches, roofs overhung by trees and properties in damp valleys will always regrow faster than a south-facing roof in open air, and we will give you a realistic expectation for your particular building rather than a sales figure.

Many customers pair a roof clean with gutter clearance, and soffit and fascia cleaning, since the access is already in place and it makes far more sense to do the whole rainwater system in one visit. We are happy to quote for any combination and price it as a single job.