Leveling a Sloping Sub-Floor

A subfloor must be level and smooth before you can install tile, carpet or floorboards. The extent of repair on a sub-floor depends on the severity of the problem and the degree of the slope. For instance, if you have a sunken section of foundation in a crawl space you would install jacks to raise the sunken section until it is level. If the concrete floor slab has sunk considerably, mudjack or inject grout into pre-drilled holes around the edges with a pump. A slightly sloping subfloor can be leveled with self-leveling compound, resulting in an even surface for tile or boards.

Pry bar
Broom
Mop
Primer
Paintbrush or trowel
5 gallon bucket
Floor leveling compound
Drill
Level
Washable marker

Instructions

- 1
  Slide a pry bar behind the wall molding around the edge of the flooring to pull it loose. Set the molding pieces aside and reinstall them after the subfloor is leveled.
- 2
  Sweep the subfloor with a broom to remove accumulated dirt and debris that may prevent the compound from adhering to the surface. Lightly mop the subfloor to remove leftover dirt, and let it dry.
- 3
  Apply a thin layer of primer or latex bonding agent to the prepared subfloor surface with a brush or trowel. Cover the corners and edges of the floor with the latex primer. Allow it to dry thoroughly for the time specified on in the directions.
- 4
  Slide a 3-foot level on the subfloor to identify the exact locations of low spots or dips. Mark these areas on the floor with a washable marker so you know where to apply the compound first.
- 5
  Prepare the floor leveling compound in a 5 gallon bucket according to the label's directions. Add cold water to the compound and mix until it reaches the consistency of soup.
- 6
  Pour the prepared compound over the marked areas on the subfloor. Smooth out the edges of the compound with a trowel to blend the compound with the surrounding floor. Work quickly to keep the quick-dry compound from setting before you get the chance to spread it over the desired area.
- 7
  Build up low areas on the subfloor by 2 to 3 inches at a time until level with the surrounding floor. Allow each layer of compound to cure thoroughly before applying another layer over it. Leave the subfloor to dry before laying carpet, floorboards or tile.

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