How to remove moss on a roof - the diy guide

TL;DR: Remove moss on a roof by brushing or scraping it off by hand on a dry day, working from the ridge down, then apply a roof biocide to kill the roots left in the tiles. Avoid pressure washing, which damages tiles and forces water under them. Light moss on a sound roof can be left alone, but heavy growth should come off before it lifts tiles or blocks the gutters.

How to remove moss on a roof

The safest way to remove moss on a roof is to brush or scrape it off by hand on a dry day, working from the ridge downwards, and then treat the tiles with a biocide to kill what is left in the surface. High-pressure jet washing is the method most people reach for and the one most likely to cause damage, which is why roofing manufacturers and trade bodies advise against it.

Here at Active Cleaning Services have been cleaning roofs for more than 30 years, and the method below is the one we have settled on after seeing which approaches last and which lead to problems later. It also covers whether moss on a roof needs removing at all, because in some cases it does not.

Does moss on a roof need removing?

Not always. The National Federation of Roofing Contractors states that moss on roof tiles is rarely a problem in itself and only needs removing when it is blocking gutters, outlets or other drainage points. The NFRC also advises against heavy-handed removal, warning that power-washing combined with unnecessary foot traffic often leaves roofs with cracked or broken tiles.

Thin layers of moss isn't really an issue, however as it builds up and becomes thicker, moss could damage your roof and cause leaks. Thick moss holds water against the tiles and keeps the surface wet long after the rain has stopped, which leaves it more exposed to frost damage through the winter. It can build up along the tile edges and lift them, letting wind-driven rain get underneath. Thicker moss also consistently falls into the gutters below, causing them to block.

On north-facing roofs in particular, moss washes off in clumps and compacts in the gutter into a dense silt that water can't pass through. The gutter overflows, the wall underneath gets saturated in water and overtime can cause a damp problem.

The sensible approach is to leave light, patchy moss alone on a roof in good condition, and to deal with it once it has become thick, has started lifting tiles, or is filling your gutters.

Should you use a pressure washer?

A roof is built to allow water to gently running down its surface. It is not built to withstand water driven upwards and sideways at high pressure. Wienerberger, one of the UK's largest tile manufacturers, warns that jet washers can damage the tile finish and strip colour from concrete tiles, and that high-pressure water can get into the interlocks and headlaps and cause leaks. Older concrete tiles can crack under the jet, and the mortar on ridges and verges can be blasted loose.

The damage to the tile surface also brings the moss back faster. Once the finish on a concrete tile has been stripped, the surface is rougher and more porous, which gives new growth an easier foothold. A roof that has been jet washed often needs cleaning again sooner than one that was left alone. We use soft washing on roofs, applying cleaning solution at low pressure and letting it do the work, and we do not use high pressure on tiles at all.

How to remove moss on a roof step by step

Survey the roof first

Before any moss comes off, check the condition of the roof for slipped, cracked or missing tiles, loose ridge tiles and failing mortar. Moss can hide existing damage, and it is far better to know what you are dealing with before you start than to discover it halfway through.

Protect the ground below

Cover plants, borders and ponds under the roofline, especially if you are using a biocide, and move cars and garden furniture out of the way before you begin.

Wait for a dry day

Dry moss comes away from the tiles much more easily than wet moss, and the roof surface is far less slippery to work near. Moss holds less water and lifts away more readily in dry conditions.

Brush and scrape from the top down

Work from the ridge towards the gutter with a stiff brush or a plastic scraper, following the direction of the tiles so you never push debris or water up under a lap. A flat-bladed weeding tool is useful for drawing moss out of the gaps between tiles. Avoid metal scrapers on softer tiles, since they can gouge the surface and create the rough texture moss prefers.

Apply a biocide

Once the bulk of the moss has gone, treat the roof with a biocide designed for roofs. Brushing alone leaves the root system in the surface pores of the tile intact, so regrowth comes back quicker unless the roof is treated straight afterwards. A biocide deals with the remaining roots and spores, along with the algae and lichen that are often growing alongside the moss. It works slowly, typically taking three to six months to kill the growth fully, which then washes away gradually in the rain. Test it on a single tile first if you are unsure how your roof will react, and follow the manufacturer's dilution rates.

Clear the gutters

Removing moss always sends debris into the gutters and downpipes, so clear them once the roof is finished. Otherwise you may find yourself back up the ladder sorting a blocked downpipe in the pouring rain.

How to stop moss growing back

Moss thrives on roofs that stay damp and shaded, so the most effective prevention is reducing both. Cutting back overhanging branches lets more light and air reach the tiles and reduces the leaf litter that moss grows in. North-facing slopes will always be more prone to moss than the rest of the roof, and it is worth accepting that they will need attention more often.

A biocide treatment every few years keeps regrowth under control on roofs that are prone to it. Some homeowners fit zinc strips along the ridge to discourage growth on the tiles below, although these can discolour the tiles over time. Keeping gutters clear also helps, because standing water and silt at the eaves give moss a foothold along the bottom courses of the roof.

Should you do it yourself?

Removing moss on a single-storey extension or a low garage roof, reached safely from a stable platform, is a manageable job for a careful homeowner. On a two-storey house the risk comes from falling rather than from the moss. Working near a pitched roof from a ladder, with tools in hand and a slippery surface in front of you, is how people end up badly hurt.

Our operatives are IPAF and PASMA trained, which covers powered access platforms and mobile towers. That allows us to use raise platforms to complete the work from beside the roof instead of on top of it, which protects the person doing the job and keeps foot traffic off the tiles.

How much does roof moss removal cost?

Costs depend on the size and pitch of the roof, how easy it is to access and how much growth there is. Published guides put manual scraping at roughly £5 to £10 per square metre and soft washing at around £15 to £20 per square metre, while MyJobQuote's January 2026 figures put the average roof clean at about £575. A biocide-only treatment for a semi-detached house is typically quoted at £150 to £400.

Do you need a roof clean in Somerset?

Contact us here at Active Cleaning Services to arrange a thorough roof clean and be confident the work is being completed by someone that knows what they are doing.