[blkgsr]

just rebuilt my deck, it's going to be enclosed below so the deck material needs to be waterproof etc

i can easily do a regular membrane through guys i know, but it's not smooth/slick for sliding chairs etc around

just need some other ideas, product names to look into

right now it's a plywood surface

[MindBomber]

You don't have a ton of options unfortunately, but my favourite one would be a waterproof surface with a false top. Basically, waterproof the surface as you would a standard flat roof, build a 2x4 frame that sits on top of the deck and is not fastened down and surface that with any standard decking material like cedar.

Exterior tile is another option, but the issue with that would be weight and whether the existing structure is capable of supporting it.

[catalin]

Composite material is great but unfortunately not cheap.

[blkgsr]

the false floor won't work, i don't have enough room from the deck to the door sill

tile isn't an option, don't want it

[fleming]

Fiberglass, if applied correctly will last for years and years with very little maintenance