Laying decking diagonally vs perpendicular to joist

Old 06-13-05, 11:06 AM
Al Degutis
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Laying decking diagonally vs perpendicular to joist

I've started the project of extending my raised deck passed the house. I originally started with corner posts on this 10'x12' extension. The beams for the extension connect to the existing deck via six 8" carriage bolts. I ended up adding middle posts along the 12' span for more stability. I put all the posts in place, added the beams and used Y-braces between the posts and beams. After installing the joists (16" center) there is some play or wobble at the end of the deck extension (the part not connected to the existing deck).

I've been told that adding the decking boards will stabilize the wobble, but I'm getting conflicting information on how to lay the boards. The current deck has the board going diagonally. I planned on removing the existing boards that stop at the end of the original deck and use new boards to provide a continuous board across the original deck and extension. I've received feedback that this is a good idea, but also feedback that I shouldn't go diagonal because it will cause the joist span to be out of center (20" instead of 16") and cause the deck to go out of square.

I'd like to go with the diagonal layout but want to be sure the deck is stable.

Pictures of the project here

Al Degutis
Old 06-13-05, 10:15 PM
Join Date: Mar 2000
Location: Arlington, WA
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Welcome to and the deck forum.

Deck boards aren't going to cure the wobble. Additional cross-bracing will.

4 corner posts and one center post? I've never seen a deck built that way. Don't know where you're at or what you used for beams and joists, but it just looks overspanned in the pictures.

Running the deck boards diagonal is fine, provided you reduce the joist spacing enough so as to not overspan the deck boards. Assuming that you will be using deck boards that can span joists that are 24" O.C., then reducing the joists to 16" O.C. and running them diagaonal is fine.
Old 06-14-05, 06:14 AM
pgtek's Avatar
Join Date: Oct 2004
Location: north Carolina
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my 2 cents

you need to add 15% extra board for you lost in the cutting

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