Install a Subfloor with Tongue and Groove Boards (Part 2)

What You'll Need
Screw gun or nail gun
Safety glasses
Dust mask
Rubber gloves
Circular saw
Tape measure
Cleaning rag
Mineral spirits
Rubber gloves
Putty knife or trowel
Wooden mallet
Masking tape
Decking screws
Subfloor adhesive

Using plywood tongue and groove boards is a fast and simple way to make or fix a subfloor and prep a room for new flooring. While removing the old subfloor, mark the locations of the nails on the walls to help you install the new sheets. After running a chalk line, lay the first sheet in place with the groove facing the line and the tongue facing the starting wall. (This is Part 2 of a 2 part series. To return to Part 1, click here.)

Step 1 – Finish Installing Sub Floor Boards

Hold the first board in place with finishing nails until you have finished the first row. Apply subfloor adhesive to the floor joists and the channels of the subfloor boards. Don’t slide the planks in the groove and smear the glue when installing the boards, just set the sheet lightly in place. Tap the board with a wood mallet to secure the joint. Nail or screw the sheets into the joists or sister boards from one end to the other without creating dips or bellies. Run a chalk line off of the floor joist and drive deck screws every 8 inches. Stagger the end joints of adjacent rows. For the best look, mix up the surface grain orientations of the subfloor panels and work from several batches at once. After you have laid as many rows of subfloor boards as you can, finish to the walls using reducer strips, T-moldings, and baby thresholds. Cut the last piece by measuring the length and width of the remaining space, or use a stencil for highly irregular edges.

Step 2 – Fill and Level Floor

After the subfloor is completely covered, inspect it to make sure that is level. If you find hills or valleys greater than 1/8 of an inch, sand them down or fill them with wood putty.

Step 3 – Allow Glue to Dry

After the plywood subfloor sheets are installed, give the adhesive time to fully cure. Try to avoid foot traffic for at least 4 hours. If you have to work on the newly installed flooring to finish a room, use a kneeler board to distribute your weight. You can move furniture back into the after 24 hours. Wait at least one week before installing vinyl, tile, carpet, or hardwood flooring. The adhesive can harden quickly, so wipe up any spills as you work using a rag and some mineral spirits. Don’t stain pre-finished flooring with the adhesive. Cover the unused part of your trowel with masking tape to make cleanup easier.

Step 4 – Install Cement Boards

You can install a second layer of cement boards on top of the first layer of plywood sheets. Just screw the boards directly into the plywood along the edges. Space the screws closer together than you did when installing the tongue and groove boards. The cement backer board provides an extra layer of insulation and protection against moisture. Use of cement boards is highly recommended for installations of vinyl and ceramic flooring in kitchens and bathrooms.