On the other hand you could take up the floor boards and have a timber
merchant make tapered pieces of wood to fit on top of the joists and level
the floor this way ( same as the tapered wood on flat roofs to give fall).
But, a big but, this OK if the slope is away from the door if this is the
case go for it, if not forget it.

Hi Mike,

This is what I had in mind. Why do the doors make a difference? Couldnt
they just be planed if they need to be?