How to Fix a Hump in a Subfloor

Measure the floor

• 1

  Measure the height difference between the hump and rest of the floor. Use a straightedge to measure the hump and other high and low points of the entire area. You may notice a difference of approximately 3 inches.

• 2

  Remove the existing flooring. To remove the existing floor, use a circular saw. Cut only the area where the hump is -- not the entire floor.

• 3

  Inspect the subfloor to see if there's any damage or a way to remove the hump without further cutting.

Removing a Hump with Sleeper System

• 4

  Eliminate the sleeper system. A sleeper system, located underneath the subfloor, is an area between the subfloor and floor. It can be as high as 1/2 inch high.

• 5

  Clean the area. Remove any debris, nails and sleepers from the area.

• 6

  Place shims on the subfloor. Nail the shims every 12-14 inches down the exposed floor. Stack them on top of one another to achieve the desired height, leaving at least 1/2 inch for the top of the subfloor.

• 7

  Place the plywood over the shims. Use a chalk line to check the evenness of the new floor.Then nail the plywood onto the floor.

• 8

  Use an edger. To smooth out the plywood with the existing subfloor, run the edger over the areas.

• 9

  Affix new floor over subfloor.

Removing a Hump with a Joist Problem

• 10

  Cut the subfloor. Use a circular saw to remove the subfloor to expose the high joist.

• 11

  Look at the joist. The joist underneath the hump may appear thicker than the joist on either side of it because of moisture.

• 12

  Shave down the higher joist. You want the joist at the same height as the other ones.

• 13

  Install the subfloor. Place the plywood over the joists and nail it down.

• 14

  Mount the new floor over the subfloor.