Use a mixture designed for wood subfloors.
Floor with low spot wood.
3 set a long straightedge tool or a straight piece of 2 by 4 inch lumber.
An underlayment is a thin layer of material sandwiched between two other materials.
Fill cracks or major voids with wood putty or a self leveling compound.
Use a trowel to spread the material then allow it to dry before proceeding.
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.
Mix the compound as directed on the package then pour it onto the low spots in the floor.
Use builder s felt or shingles stapled to the floor to fill small low spots if you.
If you are nailing the hardwood floor in place choose cementitious leveling compound that you can nail through.