I recently purchased a house with really ugly, peeling vinyl flooring in the kitchen. I ripped it all up down to the subfloor with plans to install ceramic tile. Unfortunately, I realized that the waviness (probably as much as a 3/4" change in height over 3-4 feet) is due to the floor joists being crowned and/or uneven.

This is an old house with a tongue-and-groove plank subfloor. It seems to be in reasonably good condition for its age (i.e. no water damage or warping of the subfloor itself). So I'd like to avoid ripping up the subfloor if possible.

Whats the best way to go here? I did a lot of googling on self-leveling mortars and stuff like that, but I'm not sure if it would be a good idea to pour something like that directly over this old subfloor, or if I'd be better off applying another layer of 1/2" plywood or some other material, then apply the leveling compound, then 1/2" cement board then tile.

Any advice? Now that I have it stripped down to the subfloor, am I better off just ripping it off completely so I can either plane down high joists and/or add furring strips to low ones? Like I said I'd like to avoid that, but if its really the best option I'd consider it.

Thanks!

As long as the sub-floor is in fairly good shape. I would asphalt paper the floor. Lay down wire mesh and then use self leveling cement on the floor to level it correctly. The reason for the paper is to prevent any seepage from leaking down to the basement and to prevent the sub-foor from soaking up the dampness from the leveling compound until it has a chance to properly dry. Wire mesh is there for strength.
If you do it any other way you will end up with to many layers.

Or you can remove the sub-floor and sister on the side of the joists with new boards making the tops all level with each other. Then new 3/4 inch t&g sub-floor goes on that. Stagger the joints on the end of the sheets to make the floor stronger.