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Can You Put Composite Decking Over Existing Wood Deck?

Thursday, February 08, 2024

If your wood deck is looking worn out, you may want to consider replacing it with composite decking. To do this, you’ll have to remove all of the boards and their bases and build a new deck from scratch. So, is it possible to install composite decking directly on top of a wood deck?

Yes, it is possible to install composite decking boards on top of an existing wood deck. However, it requires careful consideration and preparation to ensure a successful installation. It is important to note that while there are some benefits to this method, there are also some additional risks.

This article will show you how to install composite decking over an existing wood deck. We will also carefully analyze the pros and cons of doing so to help you understand.

Things to Consider Before Laying Composite Decking on a Wood Deck

We now know that there is nothing wrong with laying composite decking boards on an existing wood deck. However, there are a few important things to consider before beginning the installation process.

Keep in mind that the condition of the old deck will have a direct impact on the new composite decking you lay over it. You need to thoroughly inspect the existing wood decking for the type of wood, how long it has been in use, and how damaged it is. Then evaluate whether you can install composite decking boards over the existing wood deck.

The distance between joists is another important factor. For composite wood decking, the recommended spacing is 400 mm. Some wood decks are longer, so you may need to add more boards to reduce the center distance to 400 mm.

composite decking over existing

Rotting Wood Decking

Before starting, assess the condition of the existing wooden deck to ensure that it is structurally sound and free from rot, decay, or other damage. If the wood decking is in good condition, you can install composite decking directly on top of it. keep in mind that the condition of the old decking will have a direct impact on the new composite decking boards you lay on top of it.

It is unlikely that you will be able to lay composite decking on a wood deck that has rotted beyond repair. Even though composite decking material is not prone to rot. However, if it is installed on a wood deck that is rotting, the support structure it requires may begin to rot over time.

If the current deck is rotting badly, water will clog up under the new composite decking, causing the deck to rot even more. This can seriously jeopardize the longevity of the new decking and the safety of pedestrians.

Different Types of Wood

Not only that, but you should also check to see what kind of wood your current wood deck was built with. The least rot-prone types of wood are cedar, mahogany, and oak.

If a composite decking is built on top of a deck constructed with these timbers. then the longevity of the new composite decking is usually not affected.


Replacing an Existing Wood Deck

If the old wood decking has decayed beyond repair, you may need to replace it with new composite decking instead of laying new decking on top of the wood decking.

To find out the extent of the wood deck’s rot, simply run a screwdriver through a few boards. If there are a lot of areas where the wood is loose and easy to push in. Then you may need to completely replace the rotted wood decking.

If you install composite decking boards on top of a badly rotted wood deck. Then the framing of the composite decking may also begin to rot. This can lead to a serious reduction in the lifespan of the new composite decking.

Increase in Deck Height

It is important to note that installing composite decking on top of an existing wood deck will increase the height of the deck. It may therefore be necessary to adjust the height of railings, stairs, and other features accordingly. In addition, ensure proper ventilation and drainage to prevent moisture buildup between the old wood deck and the new composite decking. This is because prolonged moisture buildup may lead to mold, mildew, or rotting of the old deck framing.

Finally, follow the composite decking manufacturer‘s installation guidelines and recommendations to ensure safety and durability. In conclusion, while it is possible to install composite decking boards over an existing wood deck, careful planning and preparation are the keys to success.


How to Lay Composite Decking on an Existing Wood Deck

Laying composite decking boards over an existing wood deck is very simple. However, you should take the time to make sure they are installed correctly to avoid problems later.

If you have outdoor furniture on your wood deck, remove it before you begin. You will also need to remove the railings from your deck before you begin.

Then, use the steps below to lay the composite decking boards on the wood deck safely and efficiently.

Step 1

First, use a pry bar to pry the boards off the old wood deck. Then, you can use some of these wood decking boards to make temporary blocking lines.

After that, double-check the wood deck framing for rot to make sure everything looks good. If you find that any parts of the framing are badly rotted, you’ll need to repair or replace them before proceeding with the installation operation.

If any parts of the framing are weak or wobbly, add additional framing to support them before continuing.

Step 2

The second step is to treat any cuts in the wood deck framing with a quality wood preservative. These steps will prevent rot from occurring once they are covered with composite decking boards.

Then, cover any holes in the wood decking created with screws or nails with joist protection tape. This is done to prevent water from accumulating in the holes, which can lead to rot and mold.

Step 3

The composite wood decking now needs to be cut to the right length so that there is the right amount of space between the ends. Prepare the composite decking boards by drilling holes in them with a 3mm drill bit. This will prevent the decking boards from subsequently breaking. Then, start fastening the composite decking boards with #8 deck screws.

There is no need to pre-drill holes in composite wood decking if you use matching fasteners. Most composite decking manufacturers provide matching deck fasteners. It is recommended to screw through the wood decking only when it is absolutely necessary. For example, on the last cut deck board where hidden fasteners cannot be used.

Start laying composite wood decking from the outside of the deck and work inward. A jigsaw should be used to cut the boards around the fence posts during the laying process.


Step 4

Next, cut the center planks to the proper length. Begin the installation by moving them away from the breaker planks and toward the perimeter planks. Don’t forget to install them from the outside of the deck toward the building.

When laying the composite wood decking, make sure you use shims so that there is proper space between the planks. This is very important because the planks need enough space for thermal expansion and cold contraction. Allowing proper space between the decking planks also allows water to drain out and prevents moisture buildup.

Step 5

After laying the new composite decking over the old wood deck, there are only a few things left to do.

First, take a final look at the composite decking to make sure that all of the screws, fasteners, and nails are in place and secure. Then, make sure that each piece of composite wood decking is strong and won’t break when you put heavy objects on it.

Composite decking does not need to be sealed. If you want to seal your composite wood decking, then you need to give it enough time to dry and do it immediately.

After completing the above. You can then place your outdoor furniture on the new composite decking and reinstall the deck railings.


What Are the Advantages and Disadvantages of Laying Composite Decking over Existing Wood Deck?

The advantages of installing new composite decking this way are these:

  • It takes less time and is easier than completely removing the old deck and then building new composite decking.
  • Laying new composite decking over an old wood deck is a great way to give your outdoor space a new look.
  • Composite decking requires little maintenance. It doesn’t need to be sealed, treated, or stained, and only needs to be cleaned every so often.
  • In the long run, composite wood decking will last longer than wood. This is because it does not need to be repaired as often as wood. So it saves you money in the long run.
  • Laying composite decking is easier than wood decking and it is less likely to break during installation.
  • Because it doesn’t need to be replaced as often as wood, composite wood decking lasts a long time.
  • When it comes to protecting the earth’s environment, composite decking material is much better than wood. Because it is made from wood fibers and recycled plastic, no new trees need to be cut down to make it.
  • Composite decking boards have a wide range of colors and finishes to choose from. So you don’t need to spend time and money to color it.

Similarly, installing new composite decking on an existing wood deck can have some drawbacks:

  • If you don’t check the old wood decking and its supports for rot, you may damage the new composite decking.
  • Composite decking is more expensive to install than wood decking. But the maintenance savings you’ll realize in the long run will make up for it.
  • If you put composite decking boards over a wood deck, you will have to clean the deck more often. This is because things like dirt and water can stick between the two decks.

Frequently Asked Questions

Is Composite Decking Material Heavier than Wood?

Composite material is heavier than wood because it is made from a mixture of wood fibers and plastic polymers. In most cases, composite decking boards are about 25% heavier than wood decking.

Should Composite Decking be Secured with Screws or Nails?

It is not even a good idea to screw on composite decking boards. The reason for this is to prevent composite decking from expanding and contracting, which can cause it to bend or twist. We recommend that you use matching fasteners. If you are going to screw on composite decking boards, make sure you pre-drill the holes. This will help the deck expand and contract and give you a nice deck surface.


Do I Have to Use a Special Saw Blade to Cut Composite Decking?

Simply use a sharp, flexible saw blade to cut composite decking boards like wood. Composite decking material can be cut with a regular jigsaw, but be sure to read the instructions to find out which blade to use. We think the best blade to use is an aluminum blade that can be used for a variety of purposes.

Final Thoughts

Laying composite decking boards over an existing wood deck is easy and has many benefits. It’s an easy way to give your outdoor space a new look, and it takes less time than rebuilding your entire outdoor deck.

Keep in mind that before you begin, you’ll need to inspect the existing wood deck and its framing structure for signs of rot. If this is done, installing composite decking over your existing wood deck will go smoothly.

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