Deck Extension

Old 03-12-07, 05:47 AM
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Join Date: Dec 2005
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Deck Extension

Just wanted to get some thoughts on this. I may need an engineer.

This is what I currently have: 10X12 pressure treated deck about 37" high. 2X8 joists 16" oc running perpendicular to the house and attached to ledger board attached to the house. At the other end the joists sit on two 2X8 beams bolted on either side of three 4X4 posts parallel to the house about 10' away from the house. The three posts are evenly spaced across the width of the deck (the 12' dimension).

I want to build a small 4X12 extension on the deck (basically extending the deck 4 feet out with the same width as the current deck). The extension will be about 7" below the current deck (about 30 inches high). From my measurements, what would work perfectly from a design standpoint would be to use joist hangers to hang 2x8 joists on the beam of the current deck, extend them out the four feet past the current deck, and then rest them on beams attached to posts sunk in the ground. This would save me digging 2 or 3 post holes which would be required if I built a free standing deck as the extension.

I hope I've described this accurately. I'd like any comments on whether this seems structurally sound. Code in my area requires decks to carry 40 psf evenly distributed live load.

Old 03-12-07, 06:57 AM
Join Date: Feb 2006
Location: USA
Posts: 6,784
Received 34 Votes on 31 Posts

You have given a good description of what you have. Your plan sounds like a good one if the beam will carry the extra load. Good luck with your project.

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