How Do You Seal Composite Decking?

decking material that need sealing

Before we answer this question, keep in mind that composite decking boards are made of composite lumber, which contains wood fibre, plastic and binding agents. Composite decking does not require much maintenance compared to traditional wooden decking. That said, it is not necessary to seal composite decking; however, sealing will make periodic cleaning less necessary. Here are the steps to seal your composite decking:

Clean Composite Decking

The first thing you need to do is clean the composite decking boards to get rid of any dirt, stains, or mildew present on the deck.

Power Washer

Some recommend that you use a power washer to make cleaning more efficient and thorough as compared to scrubbing by hand. Just be careful since a high-pressure setting may damage the top layer of the composite decking.

Sealing Composite Decking

After sealing, keep in mind that any dirt left behind will be “sealed” into composite decking. Make sure the decking is thoroughly cleaned. Leave to dry before applying sealer.

Correct Choice of Cleaning Agents

Make sure you choose the right cleaning agent. Do not use chlorine bleach. Regular dishwashing soap is good since it doesn’t contain ammonia. You could also try a nature-friendly composite deck cleaner. There are several highly rated, environmentally safe products specifically formulated for cleaning composite decking and effectively removing both surface and hidden dirt, mould and mildew.

sealing composite decking

Choose Which Composite Decking Sealer to Use

After cleaning the composite decking, the next step is to start the sealing process. Choosing the best possible composite deck sealer is crucial in making sure that you are satisfied with your project once it’s complete. Water-based sealers are preferable compared to solvent-based ones. Water-based sealers have two primary advantages: 1) They do not alter the colour of the composite decking boards, unlike solvent-based products, and 2) They utilise synthetic resins, which cannot be used as a food source for algae, mould and mildew.

Tip: Always Read the Instructions

Before starting the sealing process, it is important to make sure that you read and follow the directions on properly using both the composite decking cleaner and sealer. Essential information can be seen at the back of the tin, such as drying time, number of coats to apply, time allotted between coats and other critical information.

Apply Sealer

You can apply the sealer by rolling or spraying, but always remember to back-brush. If you use a roller, back-brush the sealer right after rolling it on while it’s still wet. If you choose to spray the sealer on, just use a roller to accomplish the back-brushing. You need to back-brush because doing so breaks the surface tension of the wood, and it works the sealer into the pores of the boards. The more sealer the wood absorbs, the longer the coat will last. It is also important that you only apply as much sealer as the composite decking can easily absorb. Wipe off any excess product; if you apply more sealer than what the composite material can absorb, it will puddle on the surface and dry, leaving shiny spots on your composite decking. Furthermore, these spots will tend to flake and peel.

Leave it to Cure

Once you are done applying the composite decking sealer, having followed all the steps and the instructions on the tins, your project should look great. Don’t mess it up now by not giving your composite decking enough time to dry. Tidy up, leave your project alone for a while and come back the next day. Letting the sealer dry and cure on its own is necessary. It will be worth the wait.

Maintain Composite Decking

Some people say that composite decking is maintenance-free, but this is untrue. Even when your composite decking is properly sealed, it still needs to be maintained. Composite decking requires low maintenance, especially when sealed properly. If you see any signs of mould or mildew returning, simply wash the surface of the deck with a composite decking cleaner and a soft bristle brush. Hose it off and let it dry. Once done, just apply a single coat of clear sealer as a maintenance coat. It is that simple. With proper maintenance, your composite decking can last 25 to 30 years.


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