How to Level subfloor for hardwood

subfloor

enter image description hereI just pulled up my carpet to install 3/4 solid oak hardwood and found my floors have been built badly, very un-level. 2/3 of the floor is okay in one direction but then it drops off. It is so bad I will not be able to lay the hardwood until I fix it. From current research it look like I could build it up with 1/4 ply and glue sand it but I have no idea!!

What is the correct way to fix this issue please? The home was built this way rather than any foundation problems!

I have a pic to help show the issue-

Floor plan

Best Answer

Another way it to just glue and screw/nail long timber packers over the existing joists (on top of the old flooring). Just follow the old nails/screws.

Rip down some 2" stock exactly the height of the dip. i.e. 1/8" on the first 3/16" on the second and so on until you're putting a 3/4" packer on the last joist.

This assumes the new flooring is suitable for this configuration and is fixed at each joist and not bonded to the subfloor like parquet etc.