Is installing TREX decking over an aging wood deck a cost-effective solution despite the beams being too far apart for direct installation?
Asked by Jatin Anand 
3 months ago
Last Updated: August 20, 2024
Hey everyone, I’m having a tough time with the pricey lumber costs for replacing my two old wooden decks. I’m thinking about putting TREX decking over the existing wood, since the structure underneath is still in good condition. The only issue is that the beams are too far apart to install composite decking directly. Can anyone think of any reasons why this might not be a good idea?
Thanks for your input!
The area under the deck won’t dry and deteriorate quickly. Take out the old decking. Next, insert new joists between the existing ones for added support with TREX deck material. To further protect against the weather, cover the joists’ tops with flashing tape before installing the TREX decking. This will prolong your deck’s lifespan. Best of luck!
Moisture can become trapped beneath the trex, leading to the decay of the current decking. While it may appear okay initially, it is probable that it will eventually warp or break as the wood deteriorates.
To address this issue, eliminate the current decking, insert joists equidistant between the existing ones, and you should then be able to affix composite decking.
Oh, I didn’t even think about the moisture problem!
Hey Jim, I recently wrote a detailed explanation about restoring decks. You should check it out – it’s the most comprehensive resource available.
It’s pretty straightforward to add new joists for deck restoration.
Deck restoration involves tearing up the decking and adding additional joists where necessary.
What is the spacing between your joists?
My joists are spaced 32 inches apart. Most composite decking recommends 16 inches or less spacing.
That’s unbelievable! I bet someone already mentioned adding extra joists in between, which should do the trick. Just make sure the other joists are in decent shape. I usually advise customers against putting new lumber over old. Composite decking is very durable. Do you think the old wood will last as long as the decking? It would be a shame to have to replace the old ones in just 5 years or so.
Include additional joists.
Take out the deck boards. If the tops of the joists are worn out, turn them over. Then reattach the decking with the underside facing up if they still seem good. Otherwise, consider purchasing new decking as wood is more affordable than trex.