We’re installing hardwood flooring in our second floor master bedroom. House was built in 1993. When we pulled off the carpet we realized the floor dips in the middle. The room is 18 ft (north-south) x 14 ft (east -west) and the dip starts about 2 feet from the north and south walls. There’s a 4 ft (north-south) x 8 ft (east-west) section in the middle where the dip is about one inch.
Looking for advice on how to correct this. my first thought was self-leveler like Henry 555, but that seems like a lot and I’m a little concerned about asking the floor to support that much additional weight. I also thought about putting a 3/4” x 4 x 8 sheet of plywood or MDF in the lowest area and using self-leveler elsewhere. And finally I thought about pulling up the subfloor and shimming the joists to bring at least the worst parts of the floor level.
I’m unsure what the best option is and interested in opinions. Thanks in advance for your help!