After building a standard timber deck, one of the things that you would normally do is to seal it. There are many reasons why you should do it. But what if you have a composite deck instead?

 Should you seal the composite decking? And why is it important to seal decking? 

Sealing a Decking

If you have a composite decking or planning to build one, you may have wondered whether you should seal it or not. So, do you really need to seal a composite decking?

The answer is no. You don’t have to seal composite decking boards. 

Can you seal it? Yes. According to most composite decking manufacturers, you don’t have to apply any sealant to the boards, but you can do so if you please.

 However, it’s best to check with your supplier whether you can use a sealant or not. 

It’s the opposite for wooden decks, as you need to seal them after you install the boards. The truth is, you also need to re-apply the sealant every couple of years since it can wear off the boards. 

Why Seal a Decking?

Regardless of whether you’ll seal your composite decking or not, you may have wondered; why is it necessary or beneficial to seal a deck?

 Sealants are applied to the boards to prevent damage from the elements, especially moisture.

Since most types of softwoods are prone to moisture damage, it’s necessary to seal it and take away any moisture that can ruin the boards.

What can moisture do to the decking boards? One of the main reasons you want to prevent moisture from entering your boards is because of warping. 

Wood can easily absorb water, which makes it expand. When the moisture leaves out of the wood, it will shrink.

 The constant shrinking and expansion of the boards will eventually cause it to warp or bend, which can be detrimental to the lifespan of your decks. 

As for composites, you don’t need to worry about moisture entering the boards, even if you don’t seal it. Most composites in the market are capped, which are protected by a layer of plastic on its surface.

 The capping prevents any moisture from entering the boards, which minimizes the shrinking and expanding of the boards.

The only reason you’d want to seal your composite decking is when it has no capping, or the capping is damaged. 

Why Choose Plastic-Wood Decking?

There are many reasons why you should choose composite decking. They are beautiful and are made to last longer than wood decking.

choose plastic-wood decking

If you’re living in a place where humidity and temperature constantly changes, it’s better to choose composites as it can withstand such an environment.

 With composite decking, you don’t have to worry about shrinking and expansion of the boards. Because of its resistance to moisture damage, it can withstand warping and bending. 

Another reason to choose composites is that sealants can be costly.

While you can save money by building a wood deck instead of composites, over time, the cost of buying sealants will be much higher than what you have saved. 

Aside from sealants, you also need to stain and sand a wooden deck regularly. 

How Do You Seal a Decking?

As previously mentioned, you can still seal your deck if the manufacturers or suppliers recommend doing it.

While composite decks already have protection, a sealant applied to it can make cleaning much easier. 

So the question is, how do you seal a composite deck?

First, you will need the deck a thorough clean. It is done by sweeping all dirt and debris on the deck. Then, the deck is rinsed and scrubbed with a water-soap solution using a soft bristle brush. 

For faster cleaning, you can consider power washing the decking, only if the instructions say you can do so. After cleaning the deck, apply the sealant according to instructions. 

When choosing the right sealant, make sure to consult with your supplier. In general, you’ll want to use a water-based sealant. Let it dry and enjoy your sealed deck. 

Using a sealant is not necessary for composite decks. If you plan to use one, make sure to contact the manufacturers first. While it’s not mandatory, sealing a composite decking has its advantages. 

It gives it extra protection from moisture and can make it easier to clean. 


Unlike wood decking that needs sealing, composite decking does not need sealing. But you can seal your composite decking if you want.

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