We are buying a house with a 2 car garage made of blocks. It currently has no roof at all. Instead of building joists and a standard roof I was considering building a flat roof with a railing for a deck.

Our lot is on a hill so the back side of the garage is only a few feet off the ground level so this would work out great with minimal step up to the garage deck.

But... I'm not sure if the idea is practical as far as structurally and what I could possibly use on the decking to prevent any leaking.

I'd appreciate any suggestions!