Can I Put Composite Decking Over an Existing Wood Deck?

Replace decking

Creaking, wobbling and rotting floors are clear signs that you should replace your wood decking. It looks bad, but it’s also a safety hazard. It would help if you replaced your old wooden deck as soon as possible. Since wooden decks have a limited life span, you may want to use something a little more durable. In this case, composite decking is perfect for the job. The question is, can you put composite decking over existing wood decking? By adding composite decking over a wood deck, you will need to add additional structural support to enable it to carry the additional weight.

Putting Composite Decking Over Wood

Whether your wooden deck is old or needs replacement, you may have considered placing some composite decking over it. You might have thought that you could save time and effort by putting composites over an existing wooden deck. But the real question is, can you do such a thing?

The answer to that question is yes, you can. If an old deck is strong and sound, you can use a composite deck to cover the existing wood deck; one key point to consider is drainage and how the water will drain off the two decks. Those who have built a deck before will understand how difficult it is to accomplish this, as many complications can occur. Therefore we do not recommend building a composite deck on top of a wooden deck.

How to Check if Your Existing Wooden Deck is Sound

There are things you need to consider when deciding to place a new composite deck over an existing wooden deck.

Sound footings: A new composite deck over an existing wooden deck will add more weight. Check the existing footings are structural sound. If not, do not remove the old ones; add new ones to support the extra weight.

Condition of existing wood: Always check the posts and other framings to see if they are of treated materials. Treated wood can last longer than non-treated ones. If you notice that your screwdriver penetrates punky or softwood, it is a clear indication of rot, and you need to start all over from scratch. You can experience this rot when the post has contact with the footing or ground.

If you ignore the quality of your pre-existing deck and build a new composite decking over it, there is a good chance you will only be wasting money. So, before anything else, inspect the existing deck. If it has a few broken boards, replace them first before installing the new deck. If it is too damaged beyond repair, consider building a new deck instead. If it is a brand-new or a reasonable new deck, you might want to reconsider constructing a new one on top of it.

Should You Place Composites over Wood Decks?

can you put composite decking over existing wood decking?

You can place any decking over the existing wood decking, even composites. But is that something that you should do? No, not really. While it seems logical to place composites over existing decking, doing so has a lot of downsides. 

Before doing anything, you should first consider the quality of the existing wooden deck. How old is it? Is it new? Or is it rotting and needs replacement? Why are these questions crucial? The latter can directly affect the former when placing materials over existing decking. In the case of wooden decking, if the existing floors are old and rotting, the new materials on top will have their lifespan reduced. Even though composites are not prone to rot, the surrounding structure will suffer. Moisture will be trapped underneath and damage both pre-existing wood decking and composites. The frame or foundation will also be affected by moisture, which can cause it to rot and deteriorate. 

What if your deck is new, and you only want to replace it? Can you place composites over them? If the floor and the frame are relatively new and wood materials are pressure-treated, there’s a good chance that it won’t affect the overall quality and lifespan of your composite decking boards. It wouldn’t do as much damage as an old deck would cause, even if it did. But the question is, is there a reason why you should replace newly built or still-in-good-quality decking? Before doing anything to your floor, consider the price of the materials since composites do have a high initial cost.

What can you do instead if you know that placing composites over existing wooden decking is possible but not recommended? What if you have to replace it?

What to Do Instead?

So you want to replace your deck? What can you do? To avoid the composites being damaged by moisture and rotting, you should replace the existing wood decking. It means that you have to remove all the wooden boards and replace them with composites. You will also have to do something about the existing frame. If you want a DIY approach to this project, you can check out many instructional articles and videos. 

For sure, if you want a new composite decking, it’s not enough to place them over an existing floor, especially when the deck is old and rotting. If your wooden deck is new or of good quality, it’s possible to place the composites over it. But even so, it’s not recommended to do so. In the end, you’re the one who will decide whether you want to put composite decking over an existing wood deck. 


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