My balcony leaks. I tried to fix it last year. We put 2 layers of tar paper over the plywood that was already there. Then we put another layer of plywood over the top. I only calked the cracks and holes (realize now did this wrong). What is the best way to fix this?
I'm holding back on the smartass comments, but it's gonna be tough on this one.
There is nothing that you did here that even comes close to being a "roof".
You must keep the water out 1st and then think about building a deck on top of it that doesn't damage what you used to keep the water out.
What's your budget for this project?
There are several ways to approach this: There are paint on with mesh coatings, membranes, and metal, going from easiest to difficult.