Replacing the downstairs floor system...

newman fulltimer wrote:
If it is a foam laminatefloor the foam has broken down.I just repaired a trailer floor similar to get rot out you will have to sandwich it from under

I agree, with a laminated foam type of sub floor, soft spots are generally at the joints in the plywood panels. Since the plywood is too thin for tongue and groove, the joints depend on a good adhesive bond between the plywood and the foam in order to resist flexing. Any failure in the adhesive and the structure looses it's rigidity. Anyway, if the actually floor covering is in good condition, then rather than fix the problem from above, it is better to fix it from below by adding extra bracing between cross members directly under the soft spots.

However, if you want to repair it from above, then no need to remove cabinets. Since you aren't walking where the cabinets are located, then you won't notice any weakness there. But you do have to remove all of the exposed floor covering and spot repairs are not likely to be successful. If you cut out a section of the existing plywood and try glueing a patch, then frequently the newly created joints will soon fail. Also any adhesive you use must be compatible with the foam, bonding to it without dissolving the foam. Instead a second layer of plywood should be glued directly to the existing plywood with staggered joints, then new floor covering installed.