If you ever read the manufacturer notes (don’t worry, most don’t) on any decking, they specifically warn you not to use Bleach (Sodium Hypochlorite) or bleach directives because it will fade and discolor the composite decking. It may also lead to premature cracking, chipping, and splintering.

Not good 🙁

While you may believe that cleaning your composite deck with bleach is a great method to keep it clean and mold-free, it might actually do more harm than good.

Bleach is a super strong chemical that can wear away the top layer of your decking, making stains and fading more likely.

What Is Mold and What is it Doing to My Deck?

Mold is a fungal growth that feeds off of organic material.

Mold is common on wood, as well as leaves, twigs, and other organic debris that falls onto your deck. Mold may be a continual problem if you live near many trees.

While mold can be unsightly, it doesn’t necessarily mean your deck is dirty. In fact, mold is quite common on decks.

Mold will not damage the composite material of your deck, but it can stain the surface.

To clean mold from your composite deck, use a soft brush and soapy water. You may also use a pressure washer on a low setting.

Related: How to Clean Your Composite Deck (STEP BY STEP)

Bleach is Not the Answer

The reason why bleach is so ineffective on composite decking is that it is not made of natural wood fibers.

There’s a huge misconception that bleach can “kill it all” which is simply not true. Now, don’t get me wrong, bleach does kill bacteria and it can also fight against certain viruses, but it is not a catch-all when it comes to cleaning.

When it comes to composite decking, you should never use bleach!

Related: Does Bleach Remove Black Spots On My Patio?

But, Why?

Well, for starters, as we mentioned before, bleach can damage the surface of your deck.

In addition to damaging the surface, bleach can also lead to fading and discoloration.

While you may think that using bleach will kill any mold or mildew, it’s actually only temporary. The spores will remain in the wood and will eventually come back to life when they’re exposed to moisture.

So, not only is using bleach bad for your composite deck, it’s also ineffective in the long run.

Related: Composite Decking Pros and Cons

So, Why Do People Recommend Bleach?

To be honest, when you take a look online, various different websites and blogs simply copy each other without doing any fundamental research.

When it comes to composite decking, the general rule is that if bleach is not good for natural wood, it’s certainly not good for composite decking either.

There are some people who may recommend using a diluted bleach solution on your composite deck, but we would advise against this too.

Diluting the bleach will only make it less effective and could still lead to damage.

What Is the Long-Term Effect of Bleach?

The long-term effects of using bleach on your composite deck are quite simply, damage.

Bleach can damage the surface of your deck, making it more susceptible to fading, staining, and cracking. In addition, bleach can also lead to splintering and chipping.

So, not only is using bleach bad for your composite deck in the short term, it can also cause long-term damage.

The lewis structure of a hypochlorite anion

Sodium hypochlorite is a compound with the formula NaOCl. It is composed of a sodium cation and a hypochlorite anion; it may also be regarded as the sodium salt of hypochlorous acid.

When mixed with water, it forms a highly corrosive solution that is used as a bleaching agent and disinfectant.

Hypochlorite is unstable and decomposes readily to release chlorine, which is a powerful oxidizing agent.

Is There an Alternative to Bleach?

Yes! There are a few alternatives to using bleach on your composite deck.

One alternative is to use a vinegar solution. Vinegar is a natural disinfectant and will kill mold and mildew without damaging your deck.

The Bottom Line

Using bleach on your composite deck is not a good idea. Bleach can damage the surface, leading to fading, discoloration, and cracks. In addition, bleach is only a temporary fix for mold and mildew.

So, what’s the best way to clean your composite deck?

The best way to clean your composite deck is to use a mild soap and water solution. You can also use a pressure washer on a low setting. For tough stains, you may need to use a specialty composite deck cleaner.

In fact, you can check out an article we wrote – How to Clean Your Composite Deck, which explains in great detail how you can clean your composite deck.

Additional FAQs

Can you use a 30-second cleaner on composite decking?

Yes, you can use a 30-second cleaner on composite decking. However, we would recommend using a softer brush to avoid damaging the surface. Also, be sure to fully rinse the cleaner off the surface to avoid any streaking.

What’s the best brush for cleaning composite decking?

The best brush for cleaning composite decking is a soft bristle brush. This will help avoid any damage to the surface of your deck.

Will bleach damage Trex decking?

Yes, bleach will damage Trex decking. We would recommend using a mild soap and water solution instead. You can also use a pressure washer on a low setting. For tough stains, you may need to use a specialty composite deck cleaner.

Will bleach damage a vinyl fence?

No, because bleach will likely dry out and degrade the vinyl material. Instead, use a mild soap and water solution to clean your fence. A low-pressure washer may also be used. For severe stains, you might require a vinyl fence-specific cleaning solution.

Related: Composite Deck Boards Make Great Swimming Pool Decks

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Passionate about helping households transition to sustainable energy with helpful information and resources.

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