How To Lay Subfloor On Joists

Mastering the Art of Laying Subfloor on Joists

Installing a subfloor over joists is essential for creating a sturdy and level base for your flooring. Whether you're embarking on a home improvement project or building a new structure, understanding the process will ensure a successful installation.

Materials and Tools Required

Subflooring plywood or oriented strand board (OSB)
Joist tape or felt paper
Wood screws (1-5/8" or 2")
Drill or impact driver
Circular saw or table saw
Framing square
Measuring tape

Measuring and Cutting

Begin by measuring and marking the subflooring sheets to fit snugly between the joists. Use a framing square to ensure straight cuts and avoid any overhang. Cut the sheets using a circular saw or table saw, taking into account the expansion gap of about 1/4 inch around the perimeter.

Installing Joist Tape or Felt Paper

Before placing the subfloor, apply joist tape or felt paper to the top of the joists. This material will help prevent squeaks and moisture damage caused by condensation. Ensure it covers the entire surface, especially at the joints between joists.

Laying the Subfloor

Start laying the subfloor along one wall, perpendicular to the joists. Leave the expansion gap around the perimeter. Align the edges and secure each sheet with wood screws. Drive the screws at least 1-1/2 inches into the joists, spacing them 6-8 inches apart. Stagger the joints of adjacent sheets to enhance the overall strength of the subfloor.

Fastening the Subfloor

Once all the subfloor sheets are in place, secure them with additional wood screws. Drive the screws perpendicularly through the subfloor into the joists along the centerlines. Again, maintain a spacing of 6-8 inches and stagger the screws between rows.

Cutting and Installing Around Obstacles

When encountering obstacles such as doorways or pipes, create templates by outlining the obstacles on the subfloor sheets. Cut them carefully to fit around the obstacle and install them accordingly. Secure them securely with wood screws.

Finishing Touches

After the subfloor is fully installed, check for any protruding screws or nails. Pound them down flush with the surface using a hammer or nail set. Finally, sweep or vacuum the subfloor to remove any debris before moving on to the next step in your flooring project.

Professional Tip:

Allow the subfloor to acclimate to the temperature and humidity of the building for at least 24 hours before installation. This will help prevent warping or buckling.