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Building a wood deck over patio....

This is my first post. I was wondering what is the best way to build a wood deck over a concrete patio? I have about 8" from the top of the slab to the bottom of my door. I have read lots about how to build a deck that is atleast 18" off the ground but I need some info on how to go about building one that is on the concrete.. Any tips or info will be greatly appreciated.

Thanks, Josh

Re: Building a wood deck over patio....

place 1/2 piece of a concrete patio block on the existing patio to raise the framing and allow for drainage. Place a piece of roof shingle on the patio block to prevent moisture transmission. Support the deck joist on the patio block. Space the patio blocks to accommodate the joist size/span. Use a galvanized bent plate screwed into the joist side and s.s. expansion bolt to secure the joists to the old concrete patio. Don't forget that the patio likely slopes, so after the framing is complete shim and level. Then add your decking. The total height should be about 9 inches from top of old patio to top of new deck (assumming a 2x6 joist). All of these materials are available at Home Depot or Lowes.

Re: Building a wood deck over patio....

I would build the deck a little differently. First of all, I would double up the rim joist. That way, you can secure the rim joist opposite the exterior wall to the concrete with galvanized 4x4 post bases. Your span may require you to install one or more girders between the rim joist and the house. I would double up on these as well, and install them with more post bases. Level the ledger board, girders, and rim joist to the same plane with metal shims between the post bases and the wood. Proceed to install joists between the ledger board, the girder(s), and the rim joist with joist hangers.

Re: Building a wood deck over patio....

If you go with galvanized post feet make sure they are Z-rated or they will become corroded because of the way pressure-treated lumber is manufactured these days.

Alternatively you can use PVC post feet.

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