Decking over raised concrete patio

by Troy Reeb
(Long Beach, CA)

I understand that decking over concrete isn't a good idea due to rot. But, I can't imagine that someone hasn't figured out a way to frame and deck a concrete patio with lumber and have it last. Or, can you simply lay down composite decking directly onto the concrete and attach using glue and/or concrete anchors/screws? Can you buy composite 2x material for framing?

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May 14, 2011
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Here are some ways to build a deck over concrete patio
by: Editor - Rich Bergman

Anytime you place wood decking over a raised concrete patio the members which are in constant contact with the concrete are at long term risk of moisture damage. You have described a scenario where the best solution is to build a low profile framing structure that can be made of pressure treated sleepers like 4x4s or even 2x4s.

But keep in mind using flat 2x4s or even 4x4s poses some potential problems. The resulting sleeper will follow the lay of the concrete closely and if it is unlevel you can expect to see this in the final deck. Also undoubtedly it will have variations in level and shimming will be required. Shimming with wood will result in the wood eventually being crushed or rotting and you will have gaps and then bouncy spots in the deck. The problem then will be gaining access under that part of the deck after it is built and weighs a ton.

Shims should be non-biodegradable and high density like delrin plastic or maybe even steel.

If you built a 2x6 frame you will be a little higher above the grade but you have a more rigid deck structure and all you have to do is shim properly at all contact points under the joists and make sure its pressure treated framing lumber.

Also don't forget many composite materials are not recommended to be used like this because of the potential heat build up. Some must have at least 12" of ground clearance. Check this!

You may also wish to use some kind of concrete anchor brackets to secure the dceck to the concrete in the event of wind or weather if this is a concern.

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