How to Clean Cement Tile Roofs? (Moss, Lichen, Mildew, etc)

How to clean cement tile roofs

Greenish mold, moss, and lichen are the most common problems on a roof. These can be a result of clogged gutters, dead leaves and branches resting on the roof can lead to moisture buildup and eventual moss growth. Another problem can be white efflorescence buildup on the cement roof tiles.

Let’s see what can be done about cleaning your cement roof tiles.

How to Clean Cement Tile Roofs?

Cement tile roofs can be cleaned in several ways and with simple materials that can be easily gotten. Most of these methods do not require pressure washing, but if you prefer to use a pressure washer, the steps have been included for you.


1- Non-slip Sturdy Shoes: You need these if you’re going to be walking on the cement tiles while cleaning them.
2- Safety Harness secured to a Secured Place on the Roof: It will help you get around easily.
3- A Sturdy Ladder: If someone has to hold it at the base for you, then do just that. Don’t risk climbing a ladder you aren’t sure is safe.
4- Protective Clothing: If you’re going to be using chemicals.

Method 1: Using Bleach

Bleach is excellent in removing algae, mildew, moss, and spot-treating stains sitting on cement roof tiles. Since the roof is already outdoors, bleach poses less risk of fume inhalation to the user.

Caution: If you collect rainwater for drinking or use it to water your lawn, bleach is not recommended for cleaning your cement roof tiles. It can contaminate the water and expose you or your plants to danger.


1- Sweeping brush
2- Chlorine bleach
3- Gloves
4- Goggles
5- Old clothes
6- Water
7- Hose/ spraying can


STEP 1- Remove loose dirt and debris from your cement tiles with a sweeping brush. You can use a scraper to lightly remove stuck-on debris. Cleaning your cement tile roof with all that gunk still on it can cause damage.

STEP 2- Bleach is powerful so you need to protect yourself from any possible harm. Wear old clothes because bleach damages clothing. Wear goggles and a nose mask to protect yourself from the fumes, and also wear rubber gloves to protect your hands and skin.

STEP 3- Mix chlorine bleach with water. If your cement roof isn’t too dirty, you can mix 1 part bleach with 3 parts water. It will get rid of all surface dirt, loosen stubborn stuck-ons, and give your roof a nice shine. If there’s algae or moss on your cement roof tiles, however, you need a stronger bleach solution; Mix 1 part bleach with 2 parts water or make it 50-50.

STEP 4- Use a brush to apply the bleach solution to your cement roof. This will take time if you have a large roof, so maybe use a hose or a spraying can. Ensure the cement tiles are well saturated with the solution.

STEP 5- Let the bleach solution sit on your roof for about 20 minutes. It shouldn’t sit for longer because bleach is a powerful chemical and prolonged exposure to bleach can cause your cement roof tiles to start deteriorating or breaking down. (Source)

STEP 6- Scrub the cement tiles with a soft-bristled brush to soften algae, moss, stains, or whatever dirt may be on your cement tile roof. You can apply more bleach solution where necessary, as you clean.

STEP 7- Rinse the tiles thoroughly with running water (using a hose would be best). Bleach cannot be allowed to dry on your roof so rinse with enough water. You don’t want to leave a residue that can damage your tile roof.

STEP 8- Let the cement roof dry naturally.

Method 2: Using Oxygen Bleach

Oxygen bleach is a combination of soda ash and hydrogen peroxide. It releases oxygen when it comes in contact with water, which removes stains and dirt. It is safer than chlorine bleach and will not pose a threat to your cement tile roof.


1- Oxygen bleach
2- Water
3- Bucket
4- Hose
5- Scrub brush
6- Sweeping brush


STEP 1- Use a trowel to scrape off stuck-on dirt, algae, and moss from your cement roof tiles. Ensure the cement tiles are dry because scraping is much easier then. You can do it on a sunny day. Then use a sweeping brush to get rid of the scraped mess.

STEP 2- Add 4 oz of oxygen bleach to 1 gallon of hot water. You can use normal water but the oxygen bleach powder won’t dissolve as fast as it would in hot water. Wait for a few minutes, for the powder to dissolve in the water. This gives you a better result.

STEP 3- Spray your cement roof tiles with the solution generously by using a hose or a watering can. Then wait for about 10 minutes, for the solution to work.

STEP 4- Use a scrub brush with a long handle to scrub the roof tiles. Dunk the brush in the solution frequently as you scrub the cement tiles. If you don’t have a scrub brush with a long handle, wear rubber gloves and use a normal brush.

STEP 5- Let the solution sit on the cement tile roof after scrubbing for another 10 minutes. Then rinse the roof with water thoroughly.

Method 3: Using Sodium Hydroxide or Vinegar

Sodium Hydroxide, more commonly known as Caustic soda can not only unclog drain pipes but also clean fat deposits, and grease from cement roof tiles.

STEP 1- Use a scraper with a long handle to get rid of excess moss and lichen from your roof tiles. Stand on a sturdy ladder while doing this if you can’t walk on your roof.

Scrape the cement roof tiles from left to right and then from top to bottom. Keep scraping until all the moss falls off to the gutter. If the moss growth is extensive and has been on your roof for a while, you will need to scrape extra hard.

STEP 2- Prepare a cleaning solution. If you’re using sodium hydroxide, mix 3 tablespoons of sodium hydroxide with 1 gallon of water. If you’re using vinegar, mix 1 part vinegar with 2 parts water.

You can also use a commercial cleaner like wet and forget. Follow the instructions from the manufacturer.

STEP 3- Pour the cleaning solution after mixing into your sprayer and use a garden hose to spray your roof tiles. Start from top to bottom (Just the way you scraped it). Scraping removed excess moss with this chemical spray will kill the moss and lichen growth and ensure it doesn’t grow back for a while.

STEP 4- After saturating the cement tiles, let the chemical sit for about 10 minutes. This will give it time to seep into the cement tiles and kill moss pores and other organic growths.

STEP 5- Use clean water to rinse the cement roof tiles. Sodium hydroxide is a powerful chemical that can damage your tiles if allowed to dry and stay on your cement roof for long. Rinse with a lot of water and flush all that chemical solution down.

If you used vinegar, don't rinse immediately. Vinegar is eco-friendly and very safe to use but it takes days for it to kill lichen and moss spores. Wait for about 3 or 4 days, scrub the roof lightly to remove loose moss and lichen, then rinse thoroughly with water.

Method 4: Using a Pressure Washer

All of the cleaning methods mentioned above do not require the use of a pressure washer. Some believe that pressure washers shouldn’t be used on cement roof tiles but if you use them properly and are careful, your roof will be fine.

STEP 1- Get rid of leaves, vegetation, and any loose dirt from your roof tiles. It makes cleaning much easier.

STEP 2- Climb the ladder and Inspect your cement roof for cracks or broke tiles before you blast off a pressure washer. Using a pressure washer on damaged cement roof tiles can cause further damage. Water will seep into the cement roof and get into your home. This can cause a lot of damage and mold infestation.

STEP 3- Now start pressure washing your cement roof from a safe position. The pressure washer should be on a low setting (1500 psi or less) so you don’t damage your cement roof with excess pressure. If need be you may increase the pressure a bit if the tile grit is not falling down.

You might get need an extension for your pressure washer so you can reach further on the roof.

If you need to walk on the roof instead of staying on the ladder, make sure you wear suitable shoes and walk only on dry tiles.

Caution: Usually water is enough to clean your roof with a pressure washer. However, if you have moss and lichen growing on your roof, you can add fungicide or other chemicals to the water. This is to kill the plants and prevent further growth.

STEP 4- Rinse the cement roof tiles thoroughly and allow them to dry.


Roof tiles can be a bit challenging to clean if you do the cleaning all by yourself. You don’t always have to use a pressure washer for this job as simple dirt and debris can be cleaned with household things. Moss, mildew and lichen can be tackled with scrapping, using bleach or Caustic soda, etc.

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