The bathroom is about 4.5' wide, sloping downward from the left end of the tub to the right. I can't correct the whole thing, but plan to use some pyramiding of 3/16" or 1/4 underlayment material to get the right side where the vanity and deepest corner are level very slightly sloping back towards the left side, so that I don't have water finding it's low point at the edge of the vanity and trying to get underneath it. [The pyramiding will be beneath the final solid sheet underlayment layer that will go from one wall to the next. It will be almost entirely under the vanity and tight space between vanity and tub that will get no foot traffic, except for a few inch transition beyond the vanity.] In this way, I will end up with both sides sloping slightly to the center.
In other words, it won't be perfectly flat. It will gently slope about 1.5' from left wall to about a 1' level area where the person will be standing in front of vanity, and then start gently sloping upwards again for the remaining 2' to the right wall (beginning a few inches in front of the vanity.
So after that unwieldy description, my question is, is this a big deal? Having a perfectly flat floor is supposedly a necessary prep for Armstrong sheet vinyl, but is it *really*? What terrible things will happen if I follow my plans, and what "physics" would be at work? :)
Again, I really just need this to last a few years in a tolerable condition for a rental unit until my resources and *time* are there to remodel.