Since it's impossible to build a perfectly level
floor, or flat roof, I design and build with a
1" over 8' slope (~ 1/100). Water then flows
predictably, but 1/100 slope is sub-conscious.
That cover's the issue when a pipe breaks or
a large spill occurs, the flow is directed to
drains in the floor near the wall edges , and
away from the expensively carpeted areas.
I know inundation it not supposed to happen
but it likely will, hurricanes happen.
Do normally minded architects consider that
I'm setting my piers for my tiny 20x20 and I
just surveyed the tops for that slope.