I'm replacing a deck. Its goes out 12' from the house and 24' along it. Should the outside joists be doubled? (2 boards side by side) I'm using 2x10's for the joists. 2x8's are right on the edge for a 12 foot span. Doubling the joists will make the railing posts sturdier, although I plan on adding some blocking or Simspon brackets to make the posts stronger anyway.

Another question: should I use 2x10's or would 2x8's suffice for the joists?

  • So are there no piers in the interior under the deck? How far above the ground is this deck? May 7 '17 at 15:08
  • Just one beam at the edge of the deck. Its a "flush beam" to save overhead room for a smaller deck underneath. One side of the deck is 3 feet off the ground and the other is 16 feet off the ground.Also, I may put a roof over it. In that case, I need deck posts at the edge of it to support the roof posts.
    – BrianK
    May 8 '17 at 2:29
  • I went with 2x10's for all joists and single boards for the outside joists. I'm happy with the way it turned out.
    – BrianK
    Jul 11 '17 at 1:06

My old deck had them doubled, my new one does not. Some people double all around (sides and front) to make the deck stiffer but I think it's an overkill.

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