2x8 floor joists for a deck 2f oot OC

Anyone have good info on joist spacing for decks. I normally see 2x8 deck floor joists spaced 12" or 16" OC but had one today that was 24". Any info would be appreciated.

http://www.awc.org/Publications/DCA/DCA6/DCA6-09.pdf (pages 2,3)

Perfect Thank you Jeffrey!

The joist spacing does not rely on the size of the joist but rather the thickness of the deck boards. 2X material is ok to 24" oc. 5/4 material or trex type materials are at 16" oc when applied perpendicular to the joists and 12" when applied diagonally.

I did find that info when doing a google search before posting the question but didn’t think it was reliable.

There was 2x6 decking so we are good.
I learned something today!

Thank you, have a blessed night all.

TREX also makes a high strength decking product for 24" O.C. installation.

From Trex…
For Trex 5/4x6 deck boards, the joist spacing should be no more than 16" on center for residential applications, which is the same span generally recommended for wood. Trex 2x material should be installed at no more than 20" on center for residential applications and no more than 16" on center for commercial projects. A high strength 2x6 product is available for 24" spans. When installing Trex deck boards on a 45 degree diagonal to the joists, reduce spans by a minimum of 4 inches. Special applications/loading conditions will require engineering analysis and/or reduced spans.

At the price they charge for regular 5/4 Trex, I can’t imagine what they would charge for a high strength 2X version. Maybe your Black Amex can pay for my new deck? :wink:

Hi Nick,

I took the deck coarse and don’t remember this being covered (joist spacing). Before posting I skimmed it to see if I could find info on joist spacing but I didn’t (unless I missed it). This info would be a good addition to the coarse.

PS: internachi has been a great resource for me. As long as I am doing home inspections I will be a member of internachi!

Have a blessed day all.


You probably won’t come across High Strength TREX much, kind of a special order item.

Deck Joist Sizing and Spacing

“In general terms, joists spaced 16 inches on center can span 1.5 times in feet their depth in inches. A 2x8 up to 12 feet; 2x10 to 15 feet and 2x12 to 18 feet. The larger the deck, the larger the joists.”