Built a deck which stands 8 feet above the ground. Put off the main staircase until spring and am realizing I only have 10's when I should have ordered 12's (I do happen to have some extra 2x6x12s). The run is 120" and I have support posts midway, going to pour a 6-8" thick slab at the base with heavy connectors. Width is 36 and I plan on using 4 stringers, 12" apart. Was going to use the extra 2x6's as treads, so theyll be pretty solid and support each other well.
So my question: can I get away with the 2x10's? Should I try doing cleat-supports, using 2x6s for the treads and maybe a T support board under and spanning the 36?
I also saw a method of just running something like a 2x4 or 2x6 under the stringer (they used a 2x8 and a 2x6) to make up the difference?
I'm pretty sure 1 of these methods will be good enough to get me out of a wasting a couple hundred bucks (and a delivery) on more stringers -but I'd like input on which is my best bet. Thanks