I'm trying to level a room in preparation for the installation of laminate flooring. The laminate flooring requires the subfloor to be flat to 1/10" over 4'. The room is 17' x 12' and the walls are supported by the foundation footing. There are two joists running parallel to the 17' wall that are 4' apart. The joists are 4" x 6" beams and the subfloor is 3/4" plywood.
The problem is the two joists are 1/4" lower than the walls. The 1/4" drop is constant along the majority of the room and reduces a bit as the joists approach the end of the room. The two joists are level with each-other.
We have considered the following options to level the floor:
- Lay 1/4" hardibacker between the joists down the length of the room and screw them in place. Level remainder of the floors to the wall using quicklevel cement.
- Raise the joists by adding a 1/4" shim at the top of the piers.
We are thinking of going with option 1 because we aren't comfortable performing option 2. We are worried we don't have the skills and we may cause damage. In addition, we don't know where to get a jack to lift the beam the 1/4".
Any suggestions on how to proceed with option 1? We ran a test run with the leveling compound with mixed results. The leveler doesn't appear be 1/4" thick (still drying).