Is L/36 depth for two way slab accurate?

[boonmec]

I'm investigating floor/flat-roof options for my own three story ICF walled duplex, in an area with restrictive height zoning of 26.33 feet. Dimensions inside the concrete faces of the 6 or 8 inch walls will be 53.9 by 29.5 feet. At one end wall there will be a stairwell opening of 16.3 feet (along the shorter 29.5 ft span) by 9.9 feet (along the longer 53.9 ft side). This stairwell opening in the slab could be supported by part of the steel post stair work if required. Is the two way slab depth rule of thumb of L/36 fairly accurate, i.e. could I expect a structural guy's design to yield a 29.5/36 foot (10 inch) thickness?

Other floor systems (composite joist, composite pan, foam tees, hollow core, etc) will be the same or greater depth for a greater cost given the forming method I can make use of.

Thanks