I have a deck that is 60" high with 7 step riser. I am wanting to build a bottom wood deck/patio off of the bottom step. My questions is, can I use some of the existing 4x4 posts to tie in the bottom deck? I will be placing the outer posts in concrete?
Or would I be weakening the existing 4x4 posts by drilling carriage bolts?
I think you need new posts all the way around, but it depends on the size and the weight it will carry. I would try your local building dept. to see what their requirements are.
there is a good site called matplex.com that has some installation details and also great resource for lumber pricing