How to clean roof tiles

Over time, dirt, moss and algae can build up on your roof tiles. In order to retain the structural integrity of the roof, and ensure your home and belongings are protected from all weather conditions, it is important to keep your roof clean, and clean it relatively regularly. There are a number of ways in which you could clean roof tiles, but which methods are best and which should you avoid?

Here at Roofing Superstore we are always on hand to offer help and advice, and we’ve created a quick guide on why you need to clean roof tiles, how to clean roof tiles, and how to prevent a build up of dirt, moss and lichen.

Why clean roof tiles?

Moisture related issues

If roof moss, algae and dirt is left on roof tiles and not dealt with, it can have a number of impacts. Firstly, moss absorbs moisture easily, which not only adds weight to the roof, putting it under stress, but can also result in moisture entering the roof space. Roof tiles do not dry in the sun, as the moss, dirt and lichen act as a barrier, keeping the tiles moist, which can lead to moisture soaking through into the roof. This can seriously damage integral parts of the roof structure, such as causing timber rafters to rot, which leads to long term damage. Additionally, moisture can cause cracks and splits in your roof tiles.

Damage to structural bonds

Moss grows well on cement, which means that it often grows on the bond that joins ridge tiles, apex tiles and the roof. Growing in these places can cause significant damage, agitating and breaking bonds that are key to the structure of the roof.


Moss, algae and dirt build ups on roof tiles can also result in an overheating attic and roof space, as it covers the roof tiles, preventing heat from leaving the building. Not only does this create an uncomfortable living or working situation, it can also result in high energy bills for ventilation and air conditioning.

Blocked gutters

The presence of moss, algae or dirt on your roof tiles can also result in blockages in your roofline drainage system. The build up of moss and other materials can block the guttering that runs along the tiled roof, causing water to run down the sides of the building, which can lead to unsightly marks, but also result in damp within the walls of the property.

How to clean roof tiles

Using a pressure washer – not recommended

One of the most common methods of cleaning roof tiles is to pressure wash them, but this is something that is widely disputed. Using a high powered pressure washer could cause more damage than good, because the strength of the water stream can remove the finish of the roof tiles. The finish, which is often granular, has been designed to gradually wear off over the years, so removing that prematurely can result in a much shorter lifespan of the roof tiles. Additionally, there is a risk of flooding the roof/loft space when using a pressure washer, as the water will enter any small cracks or gaps in the roof tiles.

For these reasons, many tile manufacturers do not recommend using pressure washers on their products, and using such a method to clean roof tiles may invalidate any guarantees.

Using a trowel or stiff brush

A simple yet relatively manual method of cleaning roof tiles is to scrape off the moss, algae and dirt by hand. Using a tool such as a trowel, scrape the moss and dirt away from the tiles. The drier the day the better, because the moss and other materials will not be stuck to the tiles with moisture. Alternatively, use a stiff brush to scrape the dirt off – both methods are a quick and easy way to clean your roof tiles.

Using chemicals

A number of chemical solutions have been developed to help to clean roof tiles that experience moss and algae growth. Moss killers, fungicide and anti-moss treatments can be applied to roof tiles via a spray to kill any plant life on the roof tiles. However, this shouldn’t be done until after roof tiles have been scraped with a trowel or stiff brush, to ensure that the chemical gets into all the cracks and crevices where mould, algae and other dirt can often get trapped.

When using moss killing chemicals, remember to cover up any nearby plants and grass – the chemicals are designed to kill living organisms, not just specifically moss and algae. Additionally, ensure that any run off from the chemical does not go into any drinking water sources.

How to prevent build up of dirt and moss on roof tiles

Once roof tiles have been cleaned, we’d always recommend using a number of preventative methods which will help to keep the roof clean, safe and structurally sound.

Regularly clean roof tiles

Firstly, it is important to regularly clean roof tiles, removing any build up of dirt, moss, algae or lichen. Doing this regularly will prevent large build ups of dirt and moss, and moisture will be able to freely leave the roof space, meaning that there is no threat to the structural integrity of the roof, and the roof will also be more aesthetically pleasing.

Inspect, fix and maintain the roof

Ensure that your roof is regularly inspected and maintained, and any damaged tiles or broken sections of the roof are replaced or fixed as soon as possible. Doing this will help to keep your roof tiles clean, as there are no cracks or holes in which dirt and moss can build up.

Install copper or zinc strips

If your roof is subject to a lot of moss and lichen, you can install copper or zinc strips across the roof. Fixing copper or zinc strips along roof tiles will prevent any organisms such as moss and lichen from growing, because when it rains, the rain travels down the roof and absorbs chemicals from the metal strips. These chemicals are poisonous to plant life, so any existing moss and lichen will die off, and no more plant life can grow, because the environment is poisonous.

If you have any questions about the best method for cleaning roof tiles, or would like advice on cleaning products, feel free to call our team on 01752 692 760 or use the live chat and they will be more than happy to help.

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