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How to Clean Composite Decking

Welcome to Wash Safe™ Industries. In this step-by-step guide, we're going to teach you how to clean a composite deck safely and effectively (with less than 5% bleach) and without worry of harming your landscaping using our best-selling Spray & Clean Composite Deck Cleaner. With 13+ years of professional exterior cleaning experience, we've engineered both technique and formulations to rid decks -both wood and composite- of pesky, ugly stains from moss, mold, lichen and algae while preventing it from coming back.

You can also download and print by clicking the quick link below. Frequently asked questions and answers are also provided to help guide you along the composite deck cleaning process.


How can I tell if there is moss, mold, algae or lichen growing on my deck?

Look like this? It's probably this:

Moss on Composite Deck

Often bright green in color, Roof moss looks like Mother Nature's carpeting on your roof. It has a dense texture and usually grows in dense clumps in shady location on your roof. Roof moss will cause shingles to fail prematurely if it grows underneath them.

lichen on composite deck

Lichen on Composite

Roof lichen, seen here in a light green color, grows in bush-like, leafy structures. Lichen clusters can be small or large. The texture can be dry, and crusty which can make it extremely difficult to remove. A low pressure wash pressure washing will remove it.

Algae on composite deck - how to clean composite deck

Algae on Composite Deck

Blue-green algae and green algae are some of the most common pests that grow on composite decks. Both look like a thin film or shading, as shown in photo, and it often is found concentrated in corners and in the nooks and crannies of composite deck balusters and rails. Its appearance gives the impression of an all-over stained or discolored deck.

Black mold on a composite deck - how to clean a composite deck

Black Mold on Composite Deck

Black mold streaks on a composite deck is another common problematic pest. This is what it looks like. Often people think it's grime or grease built up and don't realize the streaks are mold. When it comes to health concerns, this type of mold can be most hazardous to health so it is important that it is tended to immediately. The color is the result of a hardy blue-green algae that has a hardened black look over time. If it's black, don't wait, clean it immediately.

How can I remove moss, mold, algae or lichen from my deck?

You do not have to be a professional to get the best results. With Spray & Clean Composite Deck Cleaner, it's easy to DIY (Do It Yourself!) and clean your Composite Deck without a pressure washer or the worry of harming your landscaping! We'll explain how in the instructions below. Another option would be to hire a professional pressure washing company. A professional pressure washer will often use a pressure washing machine to remove the moss, mold, algae and lichen and this will yield great results so long as they are using reduced pressure to clean. A homeowner can rent or purchase a small pressure washer at neighborhood cleaning supply outlet but often times you can accomplish amazing results with the solution, a soft bristle brush and a hose!

Can you clean a composite deck with bleach? How do you clean a composite deck with bleach?

We strongly caution against the use of a solution that is heavily concentrated with bleach to clean composite decks. Our Wash Safe™ Spray & Clean formula is formulated with less than 5% of sodium hypochlorite to remove stains, grime, debris, grease and other build up that comes into contact with your composite deck. Below we will show you how to clean a deck with the least amount of bleach possible in order to yield the best possible composite deck cleaning results.

What is the best composite deck cleaner for a Trex, Timbertech, Azek, Fiberon or Cali-Bamboo Composite Deck?

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best composite deck cleaner, composite deck cleaning, trex, timbertech, fiberon, cali-bamboo, azek, mold, algae, composite decks


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Our mission is to provide the world's best composite deck cleaner to clean your Trex, Timbertech, Azek, Fiberon or Cali-Bamboo deck. Our best-selling Composite Deck Cleaner, Spray & Clean, is ideal for cleaning and removing stains from moss, mildew, lichen or black algae with less than 5% bleach to avoid damage to landscaping and grass. This high-performance composite deck cleaner has been known to clean composite decks unlike any other. Customers come back year after year because its proven ability to perform deep set or "below the surface" cleaning. This solution penetrates the surface unlike anything else.

Do you sell deck cleaning products in bulk or by the pallet?

Yes, Wash Safe™ offers discounts to contractors through our PRO Program as well as discounts on all pressure washing chemicals ordered by the pallet. Email to request PRO Program pricing materials.

Perhaps you need to clean composite deck material at a sports stadium or venue, You can purchase composite deck cleaner with our discounted pallet pricing - depending on your coverage area as well as the amount of bottles you'll need. This is the most economical option when you're in need of bulk composite deck cleaning solutions.

How do I know how much roof cleaning product I need?

The way our composite deck cleaning formula works is for every 250 square feet of composite deck, you will need one gallon of Spray and Clean Composite Deck Cleaner. We also provide a breakdown below whereas amount may vary depending on how dirty your deck is.

When is the best time of day and year to clean my deck?

Morning or afternoon is the best time of day to clean your deck. When cleaning a composite deck, it is best to avoid high heat in the middle of the day so the solution is not baking on your desk.The best time to clean your composite deck is Spring after the pollen season. We also recommend cleaning in the Fall, after summer has passed and before winter snow, to avoid any debris, grease, dirt or other matter from discoloring the surface over time. It's best to go into the winter months with a deck that has been thoroughly cleaned from the wear and tear of summer.

Can I clean my composite desk using apple cider vinegar or dish soap?

If you have made a spill recently or have small spots, you can absolutely use either. These are solutions that can work topically on surfaces that are slightly unclear. If your deck is dirty or extremely dirty, you'll want to use an effective solution made for cleaning composite decks, which are porous. Our Spray & Clean Composite Deck Cleaner was made to go deep beneath the surface and clean composite decks topically as well as from the inside out. Our solution is a long term solution to clean and prevent the problem from resurfacing.



Aside from having ugly appearance, a deck covered with dirt, grime, debris and other pests can cause problems. Regular cleaning of your composite deck is necessary in order to keep it looking great and keep harmful moss, mold and algae from coming back. This is especially important if someone in your home suffers from allergies. Having a clean, like-new composite deck can also help improve property values and aid in the sale of a home. A deck on a home is a major plus but if its dirty, it can deter a potential buyer. Keeping your composite deck clean all year can be easy, you just need the right formula and tools.


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scrub brush for composite deck cleaning



Each gallon of diluted Spray & Clean will clean 250 sq. ft. of decking. However, the product may need to be diluted in different ratios depending on the condition, brand and age of your deck as well as the timing of its last cleaning. In extreme cases, Spray & Clean should be used straight without dilution. For routine (maintenance type) cleaning, Spray & Clean should be diluted 4:1 — 4 parts water to 1 part Spray & Clean, making 5 gallons total of cleaning solution.


Use extreme caution cleaning with any chemical formula. Wear protective goggles and gloves when handling cleaning solutions. If you are not skilled, comfortable or physically able, contact a professional.

Cover and avoid contact with windows, glass and raw metals (copper and aluminum) when spraying. It's best to rinse plants down before and after every cleaning application but not necessary. Avoid hydrangea petals.

Avoid contact with eyes and prolonged skin contact. Keep out of reach of children and pets. Do not ingest. If swallowed, drink water and seek immediate medical attention.

How to Clean Composite Deck with Spray & Clean Composite Deck Cleaner

Composite decking is a great use of recyclable products like cardboard, plastic, wood and other materials. It is structurally sound and will outlast wood but like everything else- it needs to be cleaned and cared for. Cleaning composite decking can be a hard to solve project but it does not have to be. With all cleaning projects, there are 3 components needed to be successful:
1. Knowledge ... 2. Equipment .... 3. Product (Spray & Clean!)
We're providing all that information here in our Do It Yourself 101.

Step 1: Determine How Much Composite Deck Cleaner You Will Need & Prepare Materials

Determine how much Spray & Clean cleaning solution you will need using the ratio chart to the right. Gather other tools. Start your project early morning or later in the afternoon on a dry day. Make sure your deck is dry. Mix Spray & Clean with warm water (hot if possible) and add complete solution to your garden pump sprayer.

dirty composite deck with mold, algae, bacteria, dirt and grime



Extremely Visible: the surface is completely covered and you see more mold, moss and algae than you see composite decking.

Use undiluted

Very Visible: Large, dark, hard-to-remove patches of moss, mold and algae.


Visible appearance of moss, mold, algae, dirt, grease and grime. This choice often selected for annual cleaning.


Recently visible: you are just starting to see moss, mold, algae, etc; surface. There is newly visible growth.


Routing cleaning: There is hardly anything on your deck. You are just cleaning to deal with spores and prevent growth.


Step 2: Saturate the Deck

Saturate the stained decking allowing the product to be absorbed by the decking. Stains will start to disappear on contact. Do not let the formula bake on the deck in direct sunlight.

composite deck cleaning trex timbertech fiberon aztak cali bamboo

Step 3: Rinse Deck with Pressure Water or Hose + Scrub Brush

Once the deck is completely saturated, Rinse it off thoroughly with water, a pressure washer and/or a scrub brush. A scrub brush will assist in the removing stains from moss, mold, algae and lichen.

For stubborn stains: If your composite deck is still showing stains after the application, you may need to reapply. Soak the deck for 2 hours or overnight then rinse (as instructed above) as needed.

If stains come back: If this is your first time cleaning the deck, sometimes dirt, grime and mold can resurface considering the solution is pulling it out from under the surface. If this purge situation happens, which it does, you will need to repeat the process.  

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Need professional help? If hiring someone to do the job is what you would rather do, a roof cleaning contractor can be found in every state now, but if you can't find one, we would be glad to speak to your local handyman and go over the cleaning process with them, just call us.


What PSI do I use to clean composite decking?

It's tough to say because every deck is different. We recommend a soft wash rinse, just slightly more pressure than a garden hose. We use our own, custom-tooled soft tip nozzles which reduce the pressure impact. Once composite decks start getting older, it becomes more porous making it easier for mold to get into the decking and stay embedded inside. Once mold starts to form, it gets worse year after year which is why more pressure is sometimes needed but it's not always needed.

Can I use Oxi Bleach / Oxygen Bleach to clean Composite Decking?

Oxygen bleach can be used with composite decks.

What do I use to clean composite deck furniture?

Clean your composite deck every year with our Spray & Clean. Use the same ratio for cleaning as you would with the deck depending on the visibility of moss, mold, algae, ec. In order to get the best results, it is best to clean your composite deck and composite furniture every yer.

What is the best way to clean a Trex Deck?

We think the best product to use for cleaning a Trex Composite Deck is our Spray & Clean Composite Deck Cleaner.

What is the best way to  clean a composite deck?

See composite deck cleaning instructions above.

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