Fix rotten subfloor from crawlspace?

Question

I am selling a house, somebody bid on it, and when it was inspected the inspector said something about the rotten subfloor under the kitchen cabinet where the sink is. This came from a backed up drain line under the house. Now this rotten area is between 3 joists (about 32" wide) and maybe a foot long so it is just under the cabinet. For some reason, instead of repairing the subfloor, the guys who put the cabinets in just stuck a piece of plywood over the entire cabinet as support for it. So my question is, how can I repair the subfloor/joists from underneath and get away with it without having to tear out the brand new cabinets............

Answer 1

if the joists are sound, you can cut the sub-floor out underneath with a sawz-all and then chisel out the material just above the joists.  Then install your replacement sub-floor in pieces and sister the joists with shorter 2x10 or whatever dimensions the full length joists are, only cut just as along as the replacement sub-floor.  Just press the sister joists up against the new sub-flooring and hammer in 5 to 8 nails on each.  Use 3" or so nails so they hold well.

depending on the conditions in the floor space, it might be almost as easy to unscrew the counter top and remove the cabinet and work from above, but it would be doable from underneath I suppose