Use builder s felt or shingles stapled to the floor to fill small low spots if you.
Floor with low spot wood.
Fill cracks or major voids with wood putty or a self leveling compound.
If the uneven floor is due to floor joists that have warped or twisted over time or were incorrectly installed the only way to level the floor is to remove the subflooring and shim the joists.
Mix the compound as directed on the package then pour it onto the low spots in the floor.
It s used to help insulate absorb sound and reduce wear on your floor.
Repair low spots in wood or concrete floors and clean them use an underlayment floor leveler or floor patch product to fix low spots in a wood or concrete subfloor.
Use deck screws or ring shank nails set into the floor joists to secure loose or squeaking pieces of wood subfloor material.
Use a trowel to spread the material then allow it to dry before proceeding.
An underlayment is a thin layer of material sandwiched between two other materials.