(guest post by Paigh Bumgarner)
Whether you’re remodeling a room or adding on an addition, one of the best things you can build for future comfort and quality is also one you can’t see in the finished product: the subfloor. If done correctly, you won’t be able to hear it, either.
Your subfloor should provide a flat, even surface on which to lay your finished floor materials. When replacing flooring finishes in a room, you may make the unpleasant discovery that the subflooring below has rotted or been damaged by common issues such as water leaks or pests. You could also discover the subflooring in your home was improperly installed or used warped wood, which could result in popping, squeaking and unevenness you can hear and feel from above on the finished floors. Pops and squeaks are not only annoying, though. As a result of the wood physically moving under pressure, a poorly installed or damaged subfloor also risks cracking or marring your finished floor, too. Regardless of the reason, here are four easy steps to take you down the path of building a new subfloor that better supports your flooring finishes.
STEP ONE: Focus on Safety Make sure the floor framing system is properly fastened to the supporting walls, beams, girders or other supports and is properly braced against rollover during floor panel installation. Using both glue and screws will provide the sturdiest fastening for your framing.
In the interest of creating that solid, flat surface for your finished floor, choose joist beams that are a high quality and straight-edged wood without warping or uneven sides. Place the joists so that they run parallel to each other at regular intervals. The size and space between the joists will depend on the kind of building codes required for your particular purpose. See floor joist or truss manufacturer installation instructions for additional information. For additions, consider creating railings connected to the framing to prevent falls. Follow all OSHA regulations and any other safety guidelines and safety practices during installation and construction.
STEP TWO: Glue the Panels – Steps two and three make up one of the most powerful tenets of subflooring installation: glue it and screw it. We recommend using polyurethane or solvent-based subfloor adhesives that conform to industry standard APA AFG-01 or ASTMD 3498 and follow manufacturer’s recommendations when installing any flooring. These recommended adhesives structurally bond the panel to the joist for a stronger, stiffer installation than panels installed with fasteners alone. If you’re skeptical, try fastening one and then fasting and gluing another. We feel confident you’ll feel the difference once fully the subfloor adhesive has been fully cured.
Apply subfloor adhesive for a strong, squeak-free installation. Photo courtesy AdvanTech.
Panels should span two or more floor joists with the long dimension perpendicular to the floor framing. When using a foam-to-gel, high-strength adhesive like AdvanTech subfloor adhesive, apply a 1/4-inch bead of adhesive to the top of the floor joists. The adhesive fills minor framing irregularities and provides a tight, even bond that helps prevent squeaks. On joists where panels meet, apply two lines of adhesive.
Immediately after applying the adhesive, lay the panel squarely on the joists. You should only apply enough adhesive for one or two panels at a time to avoid the glue drying and forming a “skin,” which could make it less effective.
STEP THREE: Screw the Panels Code-approved fasteners should penetrate framing members at least 1 inch. For panels 3/4 inch thick, use 8d ring-shank nails, screw shank nails or #8 wood screws. For panels greater than 3/4 inch, use 10d ring shank nails, screw shank nails or #9 wood screws. We recommend screws for the best results.
Install the fasteners by beginning at one corner and working your way to the remaining edges with a maximum edge distance of 3/8 to 1/2 inch. It should be a minimum of six inches on center (o.c.) on supported edges and a minimum of 12 inches at intermediate support locations. Boards like AdvanTech subflooring come with helpful pre-printed fastener guides for attachment to joists spaced at 16 inches o.c., 19.2 inches o.c. and 24 inches o.c.
STEP FOUR: Joining & Spacing Run a 1/8-inch bead of compressible adhesive in the groove but be aware that using too much will cause squeeze-out. For the next panel and all additional panels, space 4ft panel ends and other cut edges with a recommended 1/8-inch gap. An 8d nail can make a great spacer if you prefer a physical guide. Stagger end joints of adjacent panel runs. The tongue and groove profile of the boards are designed to self-space and don’t require excessive force or hammering. In fact, using excessive force can cause swell down the line.
If you have any adhesive “squeeze-out,” be sure to scrape it up immediately. Preventing glue from drying on top of the flooring removes an extra clean-up step and also ensures a flat surface for your finishes.
Repeat steps two through four and, eventually, you will have completed a sturdy, solid subfloor.
Editor’s Note: Paigh Bumgarner is Product Manager for AdvanTech. For more infomation on top-performing subfloor techniques and materials, visit AdvanTechAgame.com.