floor slopes in structural slabs

huangyhg

floor slopes in structural slabs
i have a 7" main floor structural slab over 6" void form (no crawlspace required).  the interior portion of the slab is supported off a grid of cast in place concrete friction piles c/w drop panels.
now, there are some areas that will require floor drains, and four finished sloping sides to each drain.  this results is a smaller slab depth, which theoretically reduces your "d" to a minimum at each floor drain location. (assuming the slope is say 1-2%, that could result in losing 1-2" of depth at the drain area)  is there some way of allowing the bottom of the slab to remain at a constant elevation and still design the slab to account for the floor slope?  
thicken the entire slab, using the min t at the drains.
...what boo1 said,
or,
...you could just require the preparation grading to slope with the floor slab and provide a uniform thickness.  with slight slopes like this, the rebar will simply turn and slope gradually with no specific bending required.
why the void space?
if it is needed because of potential soil swelling problems, you must maintain the 6 inch clear span below the plumbing lines, too...
focht3 - cummon...you know that expansive clays just "gush" up around pipes  
...except in s.a. tx
... and dallas, houston, shreveport, jackson, etc., etc.

would the forming to a slope would cost more than extra inch of concrete?
i wouldn't think so - at least no to any great amount.  either way the contractor must set up vertical control and check the final elevations - one is dirt with no time crunch and the other is wet concrete that is rapidly setting up.