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Why Does Your Roof Tiles Need a Cleaning?

As part of your yearly roof maintenance, be sure to undertake roof cleaning as needed as well. Dirt, moss, and algae buildup can all decrease your roof’s total lifespan by trapping moisture on the shingles and preventing the right amount of sunlight from penetrating and warming your home. Thankfully, cleaning your roof can help prevent damage and extend its lifespan. A clean roof can also help with curb appeal when selling your home and prevent unsightly mildew build up as well.

Roof cleaning may not be on your list of seasonal outdoor chores, but it probably should be. If part of your roof is in the shade, this can promote moss and algae’s growth, which prefer dark and slightly damp climates to grow in. Unfortunately, when left alone to spread, rainwater and moisture can be trapped beneath the moss, which will then begin to eat away at your roof, causing decay of the shingles and shortening its lifespan.

Occasionally, dirt and mildew may also collect on your roof. And while less harmful than moss and algae, dirt can still trap moisture on your roof and lead to eventual decay. Additionally, mould, algae, mildew, and dirt can all decrease from your home’s curb appeal lowering its value and making it more difficult to sell.

There are several different ways that you can get your roof cleaned. You can do it yourself with the right equipment or hire a professional. For dirt and mildew removal, a garden sprayer is usually necessary to get the roof clean. Moss and algae removal, however, may require professional help, particularly if the shingles have become soft or damp beneath the growth. Looking for a roof replacement? Check out Top Glaze for a wide range of roof services. 

Why Clean Roof Tiles?

If roof moss, algae and dirt are left on roof tiles and not dealt with, it can have a number of impacts. Firstly, moss absorbs moisture easily, which adds weight to the roof, putting it under stress and 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 the roof structure’s integral parts, such as causing timber rafters to rot, which leads to long-term damage. Additionally, moisture can cause cracks and splits in your roof tiles.

How To Clean Your Roof Correctly

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 roof structure.


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, but 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 buildup 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, leading to unsightly marks and dampness within the walls of the property. Top Glaze has the best range of help if you’re looking for Melbourne roof repairs.

How to Clean Roof Tiles?

If you want to try cleaning your roof yourself, your best bet is to use a garden sprayer to apply a mixture of 50% water and 50% bleach to your roof. Use a scrub brush to get the dirt and mildew off the shingles, agitating gently while keeping the roof damp until it is clean.

Pressure washing is another method of getting a roof clean, particularly when there are many buildups of leaves, moss, and dirt. However, before you attempt this method, keep in mind that not all pressure washers are the same, nor are all roofs. Using too strong a spray can damage your roof by removing some of the shingles’ granules, which shortens their lifespan. Using a high-pressure sprayer on your roof could void the manufacturer’s warranty on the shingles.

In some cases, when the moss or algae on the roof is stubborn and not coming off, a low-pressure wash system can be used to clean the roof. Some professionals will also use a low-pressure wash system to clean your roof for you as well. This should only be used as a last resort and is best left to the professionals who know how much pressure your roof can withstand without being torn up.

Using a pressure washer – not recommended.

One of the most common cleaning roof tiles is to pressure wash them, but this is widely disputed. Using a high powered pressure washer could cause more damage than good because the water stream’s strength 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 cleaning roof method 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 runoff from the chemical does not go into any drinking water sources.

How to Prevent the Buildup 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. Check out our range of roof restoration services here. 

Regularly clean roof tiles

Firstly, it is important to regularly clean roof tiles, removing any buildup of dirt, moss, algae or lichen. Doing this regularly will prevent large buildups 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.

Dos and Don’ts on Clean Roof Tiles

If you’re reading this, chances are you’re looking for roof-cleaning tips because your shingles are no longer looking new and attractive. If your roof appears dark and discoloured in some areas, you may think that mould has developed on the surfaces of the shingles. However, the black streaks you’re seeing are really colonies of blue-green algae. If you’re noticing thick, green patches on your roof instead, then you’ve got a moss problem, The north, west, and shady areas of your roof are most susceptible to these moisture-loving nuisances.

The wind or animals carry moss and algae spores from rooftop to rooftop, which is why entire neighbourhoods are often affected. Moss can seriously impact asphalt shingle performance by causing them to curl up and blow off, eventually resulting in leaks. While algae don’t harm your roof, it can impact its aesthetic appeal. Further, climbing on your roof frequently to clean off growth CAN damage your roof and shorten its lifespan by loosening the granules on your shingles. So, it’s best to know how to clean your roof properly to ensure you don’t have to do it too often.

Don’t: Use a pressure washer, which can loosen shingles and seriously damage your roof.

Do: Use a sprayer attached to a garden hose that’s filled with equal parts chlorine bleach and water. Of laundry strength liquid chlorine bleach and water. This is the best way to clean a roof if you have asphalt shingles. After spraying the roof with the mixture, allow it to sit on the surface for 15 to 20 minutes before rinsing thoroughly with clean water.

Don’t: Ignore your landscape and surrounding areas, which .the bleach solution can harm

Do: Wet plants and shrubbery thoroughly with plain water before covering them with plastic, then rinse them again after using the bleach solution on your roof.

Don’t: Assume the solution will immediately remove the growth from your roof and apply the solution again.

Do: Have patience. The algae will wash away during subsequent rainstorms, and moss will eventually loosen to the point where it can be removed with a leaf blower.

Don’t: Clean your roof on a sunny day, which will cause the bleach solution to evaporate too quickly, limiting its cleansing effects.

Do: Clean your roof on a cloudy, calm day when the wind isn’t blowing, and there’s no threat of precipitation.

Don’t: Clean your roof without taking proper safety precautions.

Do: clean your roof only after determining that you can safely walk its surface. If the slope is too steep to easily traverse, or if your house is more than one story, you should hire a pro. If you do get up on your roof, wear well-fitting shoes with slip-resistant rubber soles and be sure to don eye and skin protection.

Don’t: Wait until your roof is covered in algae or moss to take action.

Do: trim back overhanging branches to expose the roof to sunlight, and clear debris such as branches and leaves, from its surfaces with a leaf blower if needed. Keep gutters clean to ensure roofs remain as dry as possible.

Now that you know the best ways to clean a roof, be sure to follow these guidelines carefully. Note that our roof-cleaning tips only apply to asphalt shingles. If you have another type of roof, it’s important to check with your manufacturer to find out how to clean your roof. It’s wise to consult your manufacturer for roof-cleaning tips regardless of what type of shingles you have to avoid inadvertent damage.

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