To minimize the potential for floor squeaks, APA recommends that the subfloor panels should be glued and nailed to the framing using recommended fasteners and construction adhesives. For increased stiffness, tongue-and-groove or blocked panel edges also may be glued. Acceptable adhesives for installation are polyurethane or solvent-based and in accordance with APA AFG-01 or ASTM D 3498 standards.

Approved Fasteners

Panels should be fastened with wood screws, common or deformed shank nails, or other approved fasteners. Power-driven nails can be used if not overdriven. For panels up to and including 3/4″ performance category 6D deformed shank or 8D common nails are recommended. For panels, 7/8″ performance category or thicker 8D deformed shank nails are recommended.

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Installation Guidelines

  • Panel installation should start at the corner of the floor framing.
  • Start the installation with the tongue out towards the outside wall. If you don’t, the entire width as you work inward will be off.
  • Lay the panels over two or more supports with a long dimension across supports.
  • The ends must be over the supports. The end of the panels should occur approximately at the center of supports with a minimum bearing of 1/2″.
  • Stagger the panel at least two supports.
  • To avoid buckling, be sure to leave a 1/8” gap on all four sides to provide room for naturally occurring expansion, which most tongue-and-groove joints already allow.
  • If panels are tongue and groove, they should be butted lightly together. Always use a block of wood against the groove edge to minimize damage to the panel. Crushing wood fibers can close up the necessary gap leading to improper spacing issues.
  • Make sure the surface is dry and free of dirt.
  • Apply a continuous bead of ¼-inch-diameter solvent-based construction adhesive along the top of the joists, and to the tongue-and-groove panel joints. Apply only enough glue for one or two panels at a time, and completely fasten each panel before the glue is set. If the glue develops a skin, it will lose some of its strength or may not bond at all. Check manufacturer specs for setting times, and keep in mind that warm weather can accelerate those times.
  • Fasteners should be placed 3/8” from the edge and spaced 6” apart along the panel edges. And 12” apart along the intermediate supports. Make sure to install all the fasteners before glue cures.
  • Be sure to sand any uneven joists before installing flooring.
  • Flush nail or screw head. Do not “over-derive” or “raised heads”.

Common Installation Mistakes

  1. Subfloor Panels Installed Upside-Down
  2. Gluing Too Far Ahead. For efficiency, many installers prefer to lay down several panels’ worth of glue at a time, but the time delay could cause the adhesive to skim over, affecting its strength and potential noise. For best results, work no more than one panel ahead.
  3. Not Gluing the Subfloor’s Tongue-and-Groove. Applying a small bead of glue in the tongue-and-groove can significantly help reduce any movement and noise.
  4. Again, it’s tempting to tack the corners and come back to screw all the panels down at once. But by then the glue is already set. Fasten each panel fully as you go to ensure full adhesion and avoid movement and noise down the road
  5. Using Improper Fasteners. Using code-approved screws rather than nails is the best option for avoiding movement. If using nails for subfloor installation, stick with ring-shank nails; smooth nails may withdraw easier, leading to squeaks.
Resources:
  • APA’s Engineered Wood Construction Guide (Form E30) for fastener size and spacing.
  • https://buildgp.com/wp-content/uploads/2018/10/APA-floor-installation-pdf.pdf
  • https://www.huberwood.com/uploads/documents/technical/documents/2-Layer-Subfloor-with-AdvanTech-subflooring-Technical-Tip-Subflooring-AdvanTech.pdf