Frame up a box the size of the outer dimensions of your deck using 2 by 4 inch lumber.
Residential roof deck construction.
Fantastic residential roof decks.
These decks are often referred to as floating as they are not secured in place as a stand alone structure.
Then run joists connecting the front of your roof with the rear every two feet along the length of your roof.
And considering how little it takes to make a roof habitable a deck up top may deliver the biggest bang for the buck in residential construction.
Deck flooring construction for rooftop decks.
For a large deck where flat sleepers are too thin to taper you can use 2x4s or 2x6s set on edge.
The decking sits on 2x sleepers usually laid flat.
The roof deck should be properly flashed with a highly durable material that is compatible with the deck material copper lead epdm etc where it adjoins the house.
Building a deck over a flat roof is very similar to building a deck over a concrete patio.
Build the frame of the roof on the ground.
The finished walking surface of the roof deck surface should be below the level of the interior floor by at least 1 1 2 inches.
First you must make sure the roof is strong enough to support 55 lbs per square foot.