I am installing a bathroom in the lower level of a house on the concrete slab. The slab is approximately 80 years old and is far from being level. I plan on pouring a self leveling floor before tiling but I am having trouble getting info on floor prep. I have heard everything from using a vapor barrier to sand blasting the slab. As it is, the slab is structurally sound, no cracks, chips etc. There is a definite texture to the concrete- it almost looks like tiny rocks in some spots. Another possible variable is that the house is in Minnesota and therefore subject to some temperature extremes.