Greetings and thanks for all the shared experience and wisdom. Had a dishwasher leak in kitchen, had to pull up laminate plank flooring. Got everything dried out, am ready to lay new floor. It's an old house, 145 years. When I last re-furbished 11 years ago, short of pulling everything up and starting with new floor joists, I installed a beam in the basement to support the existing floor joists at their midpoint (originally a 15' span, now 7.5'. Got everything as level as I could without lifting the existing timber-joists too much. Shimmed here and there. Laid plywood over the existing pine floor. Still had wavy spots and at the time painstakingly filled the low spots with layers of tar paper. This time I'd like to avoid that and try self leveling if possible. Been reading about different products an am confused by options or even if it's possible.

If possible, I only want to spot fill, not the entire floor. The current substrate is interior, not exterior plywood. Ideally there is some self leveling product that can be used on the low spots to fill them and feather finish, lay the floor (more laminate planks. Is this possible? I read a lot about using mesh, or not using mesh and also having to maintain at least 1/8" thickness of leveling compound which to me would deform the planks if I spot filled and I'd have to do the whole room.
As you can tell, too much reading, to little experience with these products.
thanks again for any help..

 

The only issue with levelers and non concrete floors is that eventually the material will break up, especially anything that thin, 1/8".

Personally on a wood floor I find it easier to use tar paper and shingles to level!