If the kitchen connects to the dining room, but the dining room is two to three inches deeper than the kitchen. What is used to level the floors?
Depends on if this is a flip or a long term home. If it is a flip I’d would not level the two rooms. I’d just buy a nice looking threshold to use as a transition between the two spaces. It’s cheap and it will give you that depth and visual alert that there is a transition in floor heights. If you plan on keeping the home for a longer period of time I’d determine why the floors are different heights. The kitchen floor could be layers of flooring. If this where the case I’d rip out the floor and put a new one in it’s not as expensive as you think.
Two to three inches is quite a spread. Is this a slab? How big is the dining room? I wouldn’t pour concrete, but I might roll out some polyethylene film and lay down some sleepers (maybe 12-24” apart), then go over them with 5/8”-¾” plywood.
I’ve spread thinset onto a floor, then laid down concrete board and taped the joints then nailed the board to the slab with a power actuated concrete hammer (8-12” on center). After that, I poured some leveling compound. Then I spread more thinset and laid 18” travertine. It brought the level of the floor up about 1 ½”.
I’ve also painted the slab with some basement wall paint (for a vapor barrier), rolled out 6 mil polyethylene film (overlap 6”), cut 5/8” plywood to fit the floor (with less than ½” gaps between), Nailed down the plywood with a power actuated concrete hammer (12” on center), then rolled out 15# roofing tar paper, then gone over that with ¾” hardwood flooring, which I nailed down with an air hammer. That brought the floor up about 1 ½” also. I’m sure that you could use 1” plywood to bring the floor up even higher.
It depends upon how much work you want to do, what kind of floor you have, what kind of floor you want, and how messed up the floor is. I would definitely rip out any existing flooring before you try to level the sub floor.
I guess I may have misunderstood. Is this home on a slap or does it have a basement. Also are the two slabs 3" apart. or is it wood floor or ceramic. I’m not sure. I think we need more information before we can really help you out.