You can use 2x material laid flat or 4x material also as sleepers.
Sleepers roof deck.
You can do a floating deck and is really your only option.
It s best to build the wooden deck in removable sections for cleaning and maintenance of the rubber roof and repair of the membrane if ever needed.
Next you will need to install a watertight epmd rubber membrane over the top of the roof deck for protection against water infiltration in place of roofing materials.
If you want the decking surface to be level the sleepers will need to be tapered to compensate for the slope in the roof deck.
This will provide the surface for you to attach the decking.
To protect the roofing membrane set the sleepers on strips of epdm or rooftop walkway matting available from commercial roofing suppliers.
1 4 6 4 mm minimum gap where the decking meets a solid wall maximum of 3 8 9 5 mm recommended.
Deck must be designed to ensure that proper drainage and air flow are maintained.
Decking laid directly over packed soil will rot quickly and wood laid over concrete rots as well when moisture is trapped between the two materials.
3 16 4 8 mm gap between boards.
Water must be able to flow through and away from the deck.
For a large deck where flat sleepers are too thin to taper you can use 2x4s or 2x6s set on edge.
Attach the decking with screws so it can be removed later for inspection or.
However i would highly recommend that you consider a that the epdm is lying flat on the roof subfloor without any sharp objects that can puncture the edpm once sleepers are laid over top and placed under load.
Trex recommendations when using with a sleeper system.
You could glue the strips tongue sleepers or just make them a bit wider and rely on pressure to keep them in place.
It s best to be able to clean it out often.
The decking sits on 2x sleepers usually laid flat.
Rooftop decking attaches to treated wood sleepers separated from the roofing by strips of epdm.
Then you will install sleepers or flat 2x6s laid flat every 16 on top of the roof surface.
It s a wash as the deck keeps the sun off the roof which is good but it also stores a lot of debris in under there.
A sleeper system is a substructure between a solid surface and trex decking.
For repairs and removal of debris joist system access may be necessary.
A set of sleepers supports the decking and allows moisture and air to flow below it.
Sleepers are placed between the deck surface and the ground or slab below it.
Roof top deck with sleeper system install guide.
A properly constructed epdm roof should last 40 or more years.
