How to Level a Floor With Sleepers

Finished living spaces look and feel better when the walls are plumb and the floors are level. While most floors are relatively level, some are purposefully constructed on a grade, such as garage floors or basement floors that slope toward a floor drain. During a remodel or a garage conversion, it’s standard practice to level a sloping floor before installing new floor covering. Sleepers are individually cut furring strips that install directly on the sloping floor.

Things You'll Need

  • Vapor barrier (recommended)
  • Treated 2-by-4s
  • Laser level
  • Tape measure
  • Chalk line
  • Circular saw
  • Hammer drill
  • Concrete screws

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Prep and Determine Level

Install a vapor barrier, such as polyethylene film over a masonry garage or basement floor. Follow the installation instructions on the package, using the recommended glue or tape.

Locate the highest point of the floor. In a garage, this is typically at the back wall farthest from the garage doors. Place a laser level in the highest corner about 6 inches from the corner walls.

Direct the laser beam at the nearest wall, right by the corner, and make a pencil mark where the beam falls.

Rotate the laser, but do not move it from its position, and make additional marks at the three other corners in the room.

Measure from the first mark you made straight down to the floor and subtract 1 inch. For example, if it’s 4 inches from the beam mark to the concrete floor, subtract 1 inch to arrive at 3 inches. This is the control measurement that you will use to adjust the other corners.

Go to each corner and measure down from the laser beam marks the distance of the control measurement and put new marks on the wall. In our example, each new mark would be exactly 3 inches below each original laser beam mark.

Snap a chalk line from corner to corner using the new, lower set of marks. The chalk line will be level.

Build the Sleeper Perimeter

Place a treated 2-by-4, on edge, along one wall and make a mark at each end of the board where it meets the chalk line on the wall.

Lay the board flat and snap a new chalk line between the marks. This is the cut line and it should be slightly diagonal across the face of the board.

Cut along the chalk line with a circular saw and then put the board back along the wall. If one 2-by-4 isn’t long enough, you can use two or more, if necessary. Just measure and cut each one individually.

Repeat with the other walls in the room to construct the perimeter sleeper frame. At the low end of the floor slope, the boards will be thickest. At the high end, they will be 1 inch thick.

Attach the perimeter boards to the floor with concrete screws. Drill pilot holes in the boards every 12 inches before inserting concrete screws. Screw length can vary, but the standard is to use a screw that extends about 1 inch into the concrete.

Install the Sleepers

Lay out the interior sleeper pattern on 16-inch centers. This means from the middle of one sleeper to the middle of the next sleeper, it should be exactly 16 inches. Make the layout marks on the top of the perimeter boards.

Insert a small nail into the first layout mark on one perimeter board and then insert a nail into the perimeter board on the opposite side of the room – in the corresponding layout mark. The heads of the nails should stick up about 1/4 inch.

Wrap a chalk line taut between the two nails and push the line as low as it will go on the nail.

Place a treated 2-by-4, on edge, flush with the chalk line. Snap the chalk line to transfer a level line onto the board.

Cut the board with a circular saw along the chalk line and attach it to the concrete floor the same way you attached the perimeter sleeper boards. Leave about a 1/2-inch gap between the end of the board and the perimeter boards to allow for expansion.

Cut and install additional sleepers in the same manner every 16 inches, lining each up with the layout marks on the perimeter boards.

Use more than one board, if necessary to form the sleepers, but keep a space of about 1/2 inch between each to allow for expansion.

Tips & Warnings

  • You can also use sleepers on a wooden floor frame. Measure and cut the sleepers as you would for a concrete floor, but position the sleepers in one of two ways. Either line them up directly over the joists that lie beneath the subfloor, or run them perpendicular to the joists. Avoid a sleeper layout where the boards are parallel to the joists but run between them, because this configuration lacks structural support.
  • If you’re installing sleepers on a wood floor, you can use untreated 2-by-4 lumber.
  • Door adjustment is necessary if the new floor level interferes with existing doors swinging freely.
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