A Deeper Look at Sub-Flooring

Sub-flooring is perhaps the most overlooked of the four elements of a finished floor system, but it has seen significant advancements in recent years. Along with the other elements of a finished floor system, sub-flooring needs to be strong enough to resist long-term bending and buckling to ensure a solid, squeak-free finished floor. 

Read on for some sub-flooring installations tips and tricks, as well as a look into recent sub-flooring innovation.

Sub-flooring prep

Finished flooring is only as good as the sub-flooring supporting it. If the sub-flooring is not properly cleaned or is not flat or dry enough, flooring performance can suffer. Before installing the flooring, it is important to check for sub-flooring moisture problems, raised nails and swollen or raised edges that will need sanding. The plane of the subfloor needs to be flat and using a premium sub-flooring that reduces the chances of post-installation sanding can save time.

Failure to do this subfloor preparation work is a recipe for callbacks and or costly and time-consuming repairs. 

Properly install sub-flooring for best results

Design professionals can specify the best sub-flooring product and still get poor results. Builders should follow these precautions and procedures for proper installation:

• Store panels in a clean, dry area and off the ground
• Install the manufacturer’s trademark stamp downward so it can be examined during inspections (sometimes the board is installed upside-down)
• Follow manufacturer’s recommendation, typically spacing panels 3 mm (0.125 in.) apart at ends and edges. When properly mated, the tongue and groove act as a self-spacing mechanism.
• Glue no more than one panel ahead on the floor framing (applying a small bead of glue in the tongue-and groove panel can help significantly reduce movement and noise)
• Fully fasten each panel as it is installed to ensure complete adhesion and to avoid movement and noise in the future
• Employ code-approved screws rather than nails to avoid movement
• Place fasteners 9.5 mm (0.375 in.) from panel corners, and space them 152 mm (6 in.) on-center (o.c.) along the panel edges and 305 mm (12 in.) o.c. along intermediate supports (installers should place all perimeter fasteners 9.5 mm back from the nearest panel edge)
• Ensure the sub-flooring is acclimated to surrounding moisture condition before installing finished flooring

As a contracting company with more than 50 years of experience in residential framing, Schauman Construction recommends builders looking into a product because of its durability and ease of use. With LP^® TopNotch 350^®, they do not need to worry about the product falling apart in the winter months. “We experience some horrible winters in Michigan,” says Dave Schauman, president of Schauman Construction in Saginaw. “Products often sit on our jobsites in colder months, freezing and thawing and freezing again. When they finally get fully thawed and dried, they can flake or fall apart…” 

But with LP TopNotch 350, Schauman says he doesn’t have to worry about the product falling apart in the winter months. “You can tell when you walk on LP TopNotch. It’s solid. In winter months, there’s no doubt in my mind what I’m using.”

Latest advances in premium-grade sub-flooring

Some of today’s premium-grade OSB sub-flooring products pack more strands into each panel and utilize adhesives that bond wood fibers at the molecular level for exceptional performance. This gives them the density, stability and moisture resistance needed to support hardwood floors, tile flooring and floors in large homes that get exposed to moisture for many months during construction.

Some premium sub-flooring manufacturers are now partnering with leading companies in the glue and adhesive industry. The wood strands of the sub-flooring get coated with polymeric methylene diphenyl diisocyanate (pMDI) adhesives to provide maximum moisture resistance. For example, LP Legacy^® sub-flooring uses Gorilla Glue Technology^® for one of the industry's strongest, stiffest sub-floors. It's technology that homebuyers easily understand and value.

Mid-grade and premium OSB is likely to continue its dominance in the sub-flooring market because builders keep getting good results with it. Although sub-flooring and complementary products are not visible to the homeowners, residents and customers who count on them for strength and quiet performance each day, builders and designers still have the satisfaction of knowing OSB flooring products are engineered to bring out the best in each other.