[BigHendy]

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.

 

[jlhaslip]

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

 

[BigHendy]

Thanks for the response. That document has some real good info. My span from middle beam to the beam I will be overhanging is 9 feet. That is what I go off of when determining my cantilever then correct? Joists 12 oc instead of 16 doesn't change my cantilever at all?

 

[jlhaslip]

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?

 

[BigHendy]

The furthest distance I am looking at is 36 inches. The pool was built into the side of a hill and I got as close as I could when u dug the holes, while still maintaining a solid foundation around the pool.

 

[Mingledtrash]

This is the 2015 residential code.(if your in the U.S.) thought it might help. also be sure to submit your drawings for approval before you build, the new code is being adopted this year in many jurisdictions.

new code requires a 4:1 ratio on deck cantilevers.

refer to table 507.5 also 507.1 - 507.8 deals with decks.
http://codes.iccsafe.org/app/book/content/2015-I-Codes/2015%20IRC%20HTML/Chapter%205.html

 

[carpdad]

If strictly following the rule, finding you are off by a few inches and have to dig a few more footings, you may try pinning the decking with 2x4 sleeper. It reinforces the decking to each other. Inspector will pass a few inches in this case.
Little (4x4') decking I used to have for the above ground pool was build on inorganic soil/tamped hole with paver blocks I had. The inspector made me put self closing hinge and a latch on the gate but passed this "footing".