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Deck joist span and cantilever

3847 Views 6 Replies 4 Participants Last post by  carpdad
Building a deck beside a round above ground pool and have some questions. I have my 3 beams set and I'm getting ready to start laying joists. My joists need to cantilever over the beam closest to the pool and I am wondering about max cantilever. When the joist span charts list span are they talking about the span from the inner most beam to the outer most beam or is it the span between inner beam and middle beam, and then middle beam to outer beam? I am trying to calculate my max cantilever. My beams are about 8 feet apart and the outer beam is about 20 feet from the pool.

Also does going 12oc with my joists change the cantilever at all? Thanks in advance. Attached is a drawing of the layout to give an idea.

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Span would be from support to support. In your example, the span from outer to middle beam would be used in the calculations.
Typically, as a guideline only, without an Engineer involved, I use twice the joist depth to figure allowable cantilever and also require a minimum of 3 to 1 ratio for the overhang. ie: if my span between the beams is 3 feet, the cantilever would be max of 1 ft regardless of the joist depth.
An Engineer would be needed to figure the actual allowables if the actuals exceeded these two guidelines.
If we knew your location, the Code for that jurisdiction would apply, of course, and is it possible that you can run this design past a Building Inspector for your area?

See if this download helps you: http://www.fairfaxcounty.gov/dpwes/publications/decks/details.pdf
Yes, the 12 inch spacing would likely allow for a longer length of cantilever, but it is beyond my capabilities to determine that.
My information is based on using the standard 16 c/c layout and the Canadian Building Code I am familiar with. Perhaps your code book allows for different answers.

What sort of distance is there from the pool to the closest beam right now?
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