William Bronson wrote:Hey Katie, welcome to permies!
I think your block idea is good, though you could easily bang together your own form, or use a tire.
You could drive the rebar as deep as possible before before pouring the cement around it.
That should go a long way from preventing lateral movement.
Setting the form, tire or block into the gravel would help as well.
I dont think an L bracket is needed.
Glenn Herbert wrote:What direction does the prevailing wind come from, and where can storms come from? I presume you would like to have the shed roof open to the south for sun warming/drying the firewood. An 8' x 20' footprint is large enough that I don't think lateral movement of the post bases is an issue, rather uplift on the long open high side of the shed would be the thing I would want to guard against. Cross bracing on all the walls would keep the structure upright and the post bases from spreading.
I think the calculation of chimney block filled with concrete versus forms filled with concrete depends on the relative cost of the materials. I would certainly use a bracket of some sort that will let the posts be tied to the footer block mass. If you can mound the top of the footer so the post seating is self-draining that would help. Roof overhangs would keep the post bases dryer too.