(06-22-2025, 07:37 PM)Patsfan Wrote: are there vertical supports?

If so where?

(06-22-2025, 10:04 PM)MstrCarpenter Wrote: The general rule of thumb is the back span to cantilever span cannot be less than 2:1. You don't have to go all the way back to the other end of the joist you're sistering, just keep this ratio in mind. Way back when, we used to have to calculate the loads and force(s), then look up modules of elasticity and extreme force in bending to determine joist sizes and spacing. IRC is attempting to make it simple (?) by mostly providing charts and examples that work. These don't match or apply to many applications. That being said, Code allows a 36"cantilever for a balcony with 2x8's @16" O.C. (42" @12"). In the real world, I would consider just doubling up 2x6's for those with long cantilevers so it won't feel bouncy or decrease the spacing.

(06-22-2025, 05:56 PM)crokett™ Wrote: I am pretty sure the answer is yes.  We replaced our 27' round pool with a 30x15 oval.   The picture shows the pool and the existing deck. The deck is wedge-shaped sections sitting on beams.  I added a new beam parallel to the pool and about 12" from it.  Brown is the edge of the current deck and example of the joists.  Orange is the existing beams.  Green is the new beam.  All of this is approximate and not to scale. There are also more wedge sections than I show.   I will take the rim joists off the existing sections and sister new 6x6s that run from the existing inside beam to cantilever over the new beam. I'll add blocking between them close to the pool since I won't have room to fasten a rim joist to the ends. The issue is the left side around the curve of the pool. beyond where the new beam ends in th area where the existing beam is furthest from the pool wall.   It's about 30" from the existing beam to the pool wall.  Even if I run joists all the way back to the outside beam sistered to the existing I think that's too long to cantilever without support.  There are 3 or 4 joists that will need support.  So my choices are (I think)

a beam that cuts the corner attached to green (new) and orange (old)

A band joist with joist hangers to support these joists. It would tie into the ends of the new extended  joists at either end, and I can double these up if I need to.     I think I prefer this option but will have to do some mockup.  The distance across the corner is only about 6'.