To cut down the entire high area of the floor Vs. adding leveling compound to the low areas

Q: I have a living room floor that slopes away from the front entry door for about a 1/3 of the room, meaning that the floor nearest the door is higher by about 3/4″ than the rest of the room and house.

Already I only have 92″ ceiling height so I’m reluctant to add material for leveling sloped floor. I am wondering, is it reasonable to use a router or the like on leveled guides of some sort to cut down the entire high area of the floor Vs. adding leveling compound to the low areas?

I haven’t been able to find anything about removal of material like this in my searches. Might you have a suggestion?

A: You can grind or shave some of the existing sub floor down. I’m assuming what you have is 3/4 thick so to meet basic code the sub floor needs to be at least 5/8. Will shaving down 1/8 really make any difference? Otherwise, you need to remove the sub floor and shave down the joists that are too high, then sister new joists to those for added strength.

Related Q: I am renovating my kitchen. We pulled out many layers of old flooring (tile, old hardwood, plywood, etc.) and stripped it down to the original plank subfloor. The original subfloor is very uneven. My contractor levelled most of the floor by ripping 2×4 sleepers, and then nailing down 3/4′ plywood. He was not able to level all areas, so he is now going to use some type of thin-set mortar to level the remaining spots before installing the 3/4 tg hardwood. My question is… is this a normal/typical thing to use thinset mortar in this kind of application? Will this hold up over time?

A: I would not call it typical. It depends how thick this mortar is. Will the nails for the flooring be long enough to go through it into the sub floor at sufficient depth to hold down the floor? What concerns me is that the contractor went to all this effort to level the floor and didn’t do it all. Why is that?