I own a rambler that was built in the 1950's and is slab on grade so the subfloors are all concrete. An addition was put on in the 1980's that is also slab on grade. In total there is about 1600sf of concrete floors that I would like to flatten so I can install a floating engineered wood floor. There are dips throughout the floor and it slopes at the outside edges. The biggest variance is 1-1/2". There is asbestos tiles throughout most of the original house which would be either expensive or hazardous to remove. From what I understand a self leveling product would not bond to this tile and, even if we removed the tile, it would be very pricey to cover 1600 sf of subfloor with a self leveler. I heard of two unconventional alternatives that may work to level the floor: sand and layering roofing shingles. I'm curious if anyone has used either of these methods successfully. If so, what was the procedure and how long did it take? Or maybe someone has another suggestion to flatten the floor without removing all the asbestos tiles? I'm open to ideas!