concrete subfloor leveling - tall humps, deep slopes
I'm trying to prepare my uneven concrete floor for installation of T&G engineered 6" oak hardwood.
After removing the old carpet, it was immediately obvious that the concrete subfloor is not flat. I used a self-leveling laser level and found out that the whole floor has a gradual slope to it, with a big hump in the center of the room. The hump spreads across 3'x4' sq. area and at its tallest point it is about 1/2" too tall. I used a diamond blade to cut 4' long stripes around 1.5" apart and manually chiseled out the high spot. Some work still remains to be done there, but I'm now wandering how to raise the lowest spots, which are about 1.5"-2" too low and spreads across 25'-30' sq. Using SLC is probably OK, but I would need a lot of it - too much. So, my question is whether anybody has a good sugestion on how to complete this phase of leveling. Is it OK to add some small gravel to the SLC or is there some completely different method of raising such a big area.