TakingThe5th wrote:
FYI-do not use cinder blocks on this project. They can crumble. Use boards.
I would not hesitate to use 8 x 8 x 16 cinder blocks on a temporary basis long as they are 2,000 psi or better, monolithic, oriented/stacked properly, (cells vertical) and you use 2 x 8 boards "on top, and, if necessary on the bottom" of the blocks before putting any load on the blocks. Don't stack the blocks more than 2 blocks high. Putting point loads on concrete (cinder blocks) is a horrible idea and will cause early failure. The soft wood distributes the loads over the full bearing surface of the block. Think about it. I've personally designed/built block retaining walls well over 30' high. Not a problem as long as there are no point loads and you handle the lateral/overturning moments. That said, if you can't do that with confidence, just use jack stands or solid wood blocks.
Chum lee