How To Clean Composite Decking Properly [Complete Guide]

While composite decking is more durable than treated lumber, which is why it’s about twice as expensive, in some ways it’s more delicate. Using the wrong cleaner on composite decking can stain it, ruin the waterproof seal that makes it so durable, and even eat away at the decking.

With this in mind, it’s crucial that you know exactly what you should and shouldn’t use to clean a composite deck. Fortunately, there are simple cleaners that can be made from products most homeowners have in their kitchen cabinets.

For those looking for an easier solution, there are also products made specifically for cleaning decks. In this guide, we’ll discuss how to clean composite decking and provide instructions for making your own cleaner. We’ll also review what name brand cleaners are safe to use and which ones you should stay away from.

How To Clean Composite Decking

What Is the Best Way to Clean Composite Decking?

When it comes to cleaning composite decking, mild is best. Harsh cleaners that one might use on a wood deck can ruin a composite deck.

Chlorine bleach can eat into the surface of composite decking and leave permanent stains and discoloration. Trisodium Phosphate, a popular cleaner for wood decks, is also not recommended for composite decking for similar reasons.

One of the advantages of composite decking is that it has a coating that makes it easy to clean. So, you really shouldn’t need to use harsh cleaners to return your composite deck to a like-new appearance.

Instead of these powerful cleaners, consider less stringent options. Mild dishwashing liquid, such as Dawn mixed with water, is a great home remedy for cleaning a deck. Name brand cleaners such as Simple Green will also do a good job cleaning a composite deck without causing stains or discoloration.

CleanerDetails
BleachNever use bleach on composite decking as it can eat away at the material, causing discolorations and stains.
VinegarA solution of vinegar and water, when used with baking soda, is a great way to remove mold growth on composite decking.
OxiCleanUnlike chlorine bleach, OxiClean uses oxygen ions to clean, which are safe for use on composite decking.
SimpleGreenSimpleGreen uses biodegradable non-toxic ingredients, which aren’t as harsh as bleach and other cleaners, making it safe for use on composite decking.
Pressure WasherA pressure washer is safe to use with a wide nozzle and PSI at a level below 1,500.

How to Clean Composite Decking with Dish Soap

cleaning composite deckingOne of the easiest ways to remove dirt and grime for a composite deck is to use simple household dish soap. I suggest using a mild soap, such as Dawn. Begin by clearing the deck of any furniture or planters, then spray it to remove any loose dirt.

Start by mixing a few tablespoons of dish soap in a bucket of water. Pour the soapy water over the deck and use a soft-bristled brush to gently scrub any dirt loose. Use a garden hose to rinse the deck off.

How to Clean Composite Decking With Vinegar

clean trek deckingWhile there are plenty of composite deck cleaning products, a homemade cleaner using vinegar and baking soda works just as well.

Begin by clearing the deck of any furniture or potted plants. Hose off the deck to remove any loose dirt or debris.

Create a solution of two parts vinegar and one part water in a bucket, then pour the solution over the deck. Sprinkle it with baking soda. The baking soda and vinegar will react to create a bubbling reaction that will help break loose any mold or grime.

Allow the baking soda and vinegar mix to set on the deck for about 20 minutes, then use a soft-bristled brush to scrub the deck, breaking loose any mold or dirt. Rinse the deck thoroughly using a garden hose.

How to Clean Composite Deck With OxiClean

power washing trex deckOxiClean is effective because it creates a chemical reaction that raises the Ph level of water. This change in the pH level causes the positively charged dirt on the deck to become negatively charged. Once negatively charged, the dirt particles break apart from each other and the deck surface, making it easier to remove.

After clearing the deck and sweeping away any loose dirt, give the deck a good soaking with a garden hose. Next, use a soft-bristled brush to spread the OxiClean solution all over the deck.

Allow the solution to soak into the deck for about 10 minutes. This will give the OxiClean time to break negatively charge the dirt molecules. Scrub lightly, then rinse off with a hose.

Cleaning Composite Decking With Simple Green

composite deck washSimple Green works both manual cleanings as well as a pressure washer. After clearing the deck and giving it a thorough sweeping, pour Simple Green into the pressure washer’s reservoir or place the pressure washer siphon into the cleaner bottle.

Apply Simple Green to the deck, making sure to keep the tip of the pressure washer 2 feet from the deck surface to avoid damaging it. Once the cleaner has been applied, give it about 10 minutes to loosen any dirt, making sure not to allow the cleaner to dry on the deck.

Use a brush to scrub any particularly grimy sections of the deck, then rinse with the pressure washer.

To apply manually, hose down the deck’s surface, then create a solution of 2 cups of Simple Green with a gallon of water. Use a brush or pump sprayer to apply the solution to the deck and allow it to soak in for about 10 minutes.

Scrub dirty sections, then rinse with a hose, making sure all cleaner and grime are removed from the deck surface.

Power Washing Composite Decks

power wash composite deckA power washer can be an effective way of cleaning composite decks. The high-pressure water allows you to remove more dirt than one can remove manually while completing the job in about half the time.

That said, there are dangers to using a power washer. Though composite decking is more durable than real wood, it’s softer, which means it’s more susceptible to etching from a power washer. Using too narrow a nozzle in combination with a high PSI can cause the power washer to do irreparable damage to the decking.

With that in mind, it’s important to take a few precautions when using a pressure washer. Use a broad fan pattern and use a PSI no greater than 3,100 PSI to avoid the risk of denting the boards.

While washing, make sure to keep the nozzle head at least 8 inches away from the deck surface and move the wand in the same direction as the grain.

Begin by adding a safe cleaner to the reservoir, then spray the deck with soap. Give the soap time to penetrate the dirt. If there are any particularly dirty sections of the deck, use a brush to help work the grime-free.

Use a fan tip to rinse the boards, making sure to keep the nozzle a safe distance from the boards while working in the same direction as the grain. Make sure all soap is removed to avoid a film from forming once the deck dries.

Cleaning Composite Decking Tips

There are a few tips to consider when cleaning a composite deck for achieving the best and most long-lasting results.

Clean Gaps Between Deck Boards

While most people go to great pains to clean the decking surface, they forget about the gaps, which is an ideal place for mold to grow. Make sure to clear all the gaps between the decking while cleaning.

Any organic material caught between the gaps in the deck can serve as food for mold to feed on and grow.

Use the Right Cleaner

Make sure to use the right materials. While aggressively scrubbing a wood deck with a stiff-bristled brush may be okay for a wood deck, that approach can damage a composite deck.

Remember, composite decks are softer than wood decks. Use a soft-bristled brush and be conscious of how much elbow grease you use when scrubbing to avoid scarring the surface.

Protect Your Deck After Cleaning

Once clean, take the extra step to prevent mold from returning to the composite decking by applying a moisture barrier. Products such as UltraBan are safe for composite decking and protect against mold and mildew growth.

Never use a sealant on composite decking as that can trap moisture inside the boards, causing rot and promoting mold growth.

Best Composite Deck Cleaner

While home remedies are an effective means of cleaning a deck, there are several deck cleaning products that are safe for cleaning composite decks. As with any cleaner you use to clean your composite deck, it’s always wise to test the cleaner on a small section before applying it to your entire deck.

1. Mold Armor Deck Cleaner

composite deck cleanerMold Armor Deck Cleaner is a great option for those who either don’t have a power washer or who don’t want to risk damaging their composite decking by using one. Mold Armor consists of a concentrated solution that attaches to a standard garden hose.

To apply, simply screw onto the hose end, turn on the water, and spray the entire deck. Allow the solution 10 minutes to soak in and break up dirt and kill mold growth, then remove by rinsing with clean water. One 64-ounce bottle covers about 900 square feet.

2. Simple Green Deck Pressure Washer Cleaner

how to clean composite decking with bleachGetting mold off of a deck can be a challenge. And while home remedies often work, they aren’t necessarily safe for use with a pressure washer. This concentrated formula from Simple Green is.

It uses safe ingredients, including ethyl alcohol and hydrogen peroxide, to cut into grime and kill mold. Simply apply it to the reservoir of the pressure washer and apply using a wide fan nozzle. In addition to removing mold, this wash is also effective at removing other stains, including tree sap, grease, and oil.

3. DeckMAX Concentrate Composite & Wood Deck Cleaner Kit

Deck Cleaner KitDeckMAX deck cleaner is well-regarded for its ability to quickly cut through grease, grime, and mold to bring composite decking back to a like-new appearance. It’s especially good at removing black and green mold, which can be notoriously difficult to get off of decking.

To use, dilute with 3 parts water to 1 part cleaner, pour onto the deck, and allow to soak in for two minutes. Scrub, then rinse clean. DeckMAX comes in 1-gallon containers and includes a soft bristle brush for scrubbing.

DeckMAX is solvent-free and produces no VOCs, making it safer to work with than some of the other deck cleaning products on the market. It also happens to be one of the more expensive deck cleaners on the market.

How to Remove Mold and Stains From Composite Deck

While most of the cleaners described above will do a good job of removing dirt and grime from a deck surface, getting rid of certain types of stains can be a bigger challenge. In this section, we’ll review some of the best ways for safely removing the most common substances that stain composite decking.

Mold, Algae, and Mildew

Most composite decking has a vinyl cap that prevents moisture from infiltrating the decking and causing mold and mildew to grow. That said, sometimes this cap can crack and fail. It’s crucial to identify these issues so you can properly seal these cracks before mold has taken hold.

While bleach is the most effective way to kill mold, don’t use bleach as it can also eat into the composite decking and damage it. Vinegar is the best solution for removing mold from a deck because it has a low pH of 2.5. This acidic composition allows it to kill mold, algae, and mildew.

Create a solution of vinegar and water and apply it to the deck. Sprinkle on some baking soda, which will cause the solution to fizz, which helps to break up the mold. Allow it to soak in for about 10 minutes. Use a soft-bristled brush to remove the mold, then rinse with a hose.

Grease and Oil

Decks are popular places for al fresco dining and outdoor cooking, so it should come as no surprise that grease and oil are common deck stains.

The key to removing grease and oil stains is to get to them early. These stains are relatively easy to remove with grease-cutting dish soap if treated and cleaned within a week.

However, if you allow the stain to stay on the surface, it can eventually soak into the boards, making them much more difficult to clean.

Some composite decking manufacturers will even void the warranty on the decking if you allow oil to set. To remove oil, create a mix of warm soapy water and apply it to the stain. Scrub with a soft-bristled brush in the same direction as the grain to remove the stain.

Pollen

For many homeowners, the arrival of spring brings with it a layer of yellow dust on every exterior surface of the home. Pollen is, for the most part, easy to remove from composite decking. Simply wash it away using a garden hose.

However, if the pollen is allowed to remain on the composite decking for a long period, it can be more difficult to remove. For stubborn pollen, create a warm soapy dish detergent solution and pour it over the stained area. Scrub with a soft-bristled brush to remove, then rinse.

Often, if pollen is left on a deck too long, it will breed mold. If the pollen is difficult to remove, you’re likely dealing with yellow mold. Use the method described above for mold removal to eliminate it.

Food

Food and beverages can be one of the worst offenders when it comes to staining. Fortunately, food stains are relatively easy to clean from composite decks.

While spilling a glass of wine on a wood deck can be challenging to clean, the same is not the case for composite decks.

Composite decks have a waterproof seal that prevents liquids from soaking into the decking. That means that any spills, including red wine, can be easily cleaned up with a paper towel.

If cleaning the spill is more difficult, it could indicate that the decking seal has failed. If that’s the case, check the warranty on your decking to see if you should make a claim.

Pine Sap

For those with decks surrounded by tall evergreens, pine sap on the deck can be a major problem. Pine sap is notoriously difficult to remove, especially during warmer months.

The best way to remove pine sap is to wait until winter when temperatures drop below freezing and the sap hardens.

In its hardened state, you can use a putty knife to gently chip the sap away from the surface. If you don’t want to wait until winter or live in a climate that rarely drops below freezing, try a dish soap and water solution. Apply the solution to the sap and gently scrub it with a sponge.

If this effort fails, you can try a cleaner such as Goo Gone. First, make sure to test the product on an inconspicuous part of the deck. If it does not cause any discoloration, then apply it to the tree sap. Allow it to soak in for about 30 minutes, then use a putty knife to remove it.

Conclusion

While no one likes to see mold, grime, and dirt building up on their expensive composite deck, the good news is it’s relatively easy to clean. One of the advantages of composite decking is its waterproof seal that prevents most substances from soaking into it.

This means that most dirt will easily clean off its surface with a little dish detergent and vinegar and a soft brush. For more caked-on grime, there are more powerful cleaning products that will do the trick without harming the decking.

While cleaning composite decking is in many ways easier to clean than wood decking, it’s more susceptible to damage from cleaning. Harsh chemicals such as bleach and TSP should be avoided as they can eat away at composite decking. Likewise, pressure washing a deck should be done with care to avoid scarring the deck.

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