Laying a Plywood Subfloor

A well-installed subfloor will keep the upper layer level and well-insulated and will help prevent a squeaky floor. Plywood is the most common type of subfloor in new homes.

Step 1.  Plan Ahead

Plywood is rated for use, based on whether it’s for interior or exterior applications, and what type of material you plan to use for the finished floor. Available in standard sheets of 4 X 8 ft (1.2 X 2.5 m), your work will be easier if you minimize the number of cuts you need to make to cover the floor. Lay out your floor carefully before you start attaching sheets to the joists. Also, plan the layout so that the cut edges are against the perimeter of the room. Make sure the sheets are spaced evenly and butt each sheet tightly. The first step is to snap a line across the floor joists to mark the position of the first sheet of plywood.

 Step 2.  Prepare Floor Joists

Apply a consistent bead of construction adhesive on the floor joists.

 Step 3.  Laying the First Piece

Keeping a space of about 1/8 inches (3 mm) away from the walls to allow the material to expand, lay the first piece of plywood on the chalk line.

 Step 4.  Attach to Joists

Starting at one end of the floor, drive nails in every 6 inches (150 mm) along the joists. Screws or staples may also be used.

 Step 5.  Preparing to Cut

To cut plywood to size, use a pair of sawhorses and 2 x 4s to create a stable cutting station.

 Step 6.  Cutting

Using a circular saw with the depth of the blade at 1/2 in (13 mm) deeper than the plywood sheet, cut the plywood to size.

 Step 7.  Laying Plywood

Lay additional pieces of plywood, inserting the tongue into the groove joints of each piece of plywood.

 Step 8.  Fitting

Use a piece of lumber as a smash block to protect the plywood tongue. Smash the additional pieces of plywood in place.

 Step 9.  Leveling and Finishing

Check the butt joints of each piece of plywood to make sure the floor is level. If a sheet is raised, drive extra staples (or nails) to force the sheet into place. Using a flat trowel, cover all of the seams and fasteners with reinforced flooring patch. Sand the floor smooth with a hand sander.