Leveling A Floor With Shims
Leveling the floor with shims is when you attach thin wedge shaped pieces of wood on top of the low areas of the joists to make the top joists even.
Leveling a floor with shims. When you are using more than one layer of shingles stagger or stair step the shingles. Step 6 screw the sheets of 3 8 inch thick plywood over the shingles using a drill and 2 to 2 1 2 inch subfloor screws to attach them to the entire floor. Set the fence to the distance of the jig and 2x4 making sure to set that distance to the far side of the blade.
Cut sheets of 3 8 inch plywood to size with a circular saw to cover the entire floor. Set the 2x4 into the jig screw it tightly into place. To shim the floor take a straightedge or a level and look for imperfections in the flatness of the floor and determine if it needs to be raised or lowered.
This may require either sanding high spots or shimming with shingles in the low spots to build them up. Cut the straight 2x4 to the length of the required shim. Shim up the subfloor as an alternative to a level compound for long lengths of a floor that are out of level with the joists.
Place wood shims between the subfloor and the top of the floor joist. 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.