Second Floor Sub-Flooring: Choosing the Right Sub-Floor for Second Stories

Few things are more downright frustrating than a tattletale squeaky floor—especially irksome squeaks that come from the floor above. For homes with multiple stories or multifamily structures, reducing floor noise is critical for the comforts of the people who live there. As with most problems, the solution is often found in the early stages of construction and selecting just the right second floor sub-floor.

What Causes Squeaky Floors? 

Creaky floors occur when there’s movement between two or more floor system components, such as when the substrate and nails rub against one another. Squeaky second floors are much more troublesome because they annoy people on two floors.

We asked Jeff Jayne, OSB/EWP Process Product Development Manager at LP, about ways to reduce floor squeaks when building single residential homes with multiple floors or multi-story condos and apartments. 

“Wood is not a perfect science. After it acclimates to surrounding moisture conditions, it still moves to some degree. One of the best ways to reduce movement is to glue the sub-flooring to the structural supports,” says Jayne. 

LP Legacy® Premium Sub-Floor Adhesive helps increase overall floor stiffness and can prevent squeaks by creating a tight seal between the floor joists and sub-floor. When used with LP Legacy® Premium Sub-Flooring, LP Legacy Adhesive offers a strong and quiet sub-floor system—and pairing the two adds coverage for squeaks alongside a lifetime limited warranty. 

Read the complete warranty details for LP Legacy Premium Sub-Flooring here.

How to Reduce Squeaks on Second Floors

“During construction, the top floor of a build may be exposed to the elements for a long period of time,” says Jayne. “Before the roof, doors and windows are installed, the adhesive and sub-flooring must perform well in very harsh conditions.”

It is also critical to use proper sub-floor fasteners and to ensure that they hit their mark—the supports.

LP Legacy Premium Sub-Floor Adhesive has been performance-tested and demonstrates the ability to withstand extreme weather conditions and protect against squeaks. The premium adhesive can even be applied to wet, dry or frozen lumber, giving builders greater flexibility.  

How Is LP Legacy Adhesive Better than Conventional Adhesive?

“The LP Legacy adhesive is polyurethane-based, making it a premium adhesive,” says Jayne. “The adhesive expands when applied to create a tight seal, even in small gaps, between panels and supports. This goes a long way in eliminating squeaks.” 

Ready-to-use and gun-applied, initial cure only takes 4 hours and the adhesive reaches full cure in 24 hours. 

Determining Second Floor Subfloor Thickness

Customers may ask if the second floor joist depth is different or whether second floor subfloor thickness needs to be greater. The thickness of OSB subfloor panels in a floor system is usually determined by the spacing of the joists. A wider span could create more deflection in the sub-flooring and a greater opportunity for movement, which can lead to squeaks. Builders can combat this deflection by using a thicker and/or stiffer subfloor. 

“When a worker or occupant is walking between the floor supports you may have deflection, especially with a commodity-grade panel,” explains Jayne. “LP Legacy Premium Sub-Flooring is engineered to reduce deflection, which can result in fewer squeaks.” 

To see how much sub-flooring can deflect between supports, Kyle Stumpenhorst of @rrbuildings looked at the difference between commodity-grade OSB sub-floors and LP Legacy Premium Sub-Flooring panels. Setting up the camera to view the deflection, Stumpenhorst walked across both panels: the commodity OSB visibly deflected while LP Legacy sub-flooring remained stiff with less deflection. 

“Builders often use LP Legacy Premium Sub-Flooring and Adhesive in areas where high-end flooring like hardwood or tile is used or areas that carry the heaviest uniform and concentrated loads,” says Jayne.

Watch this video to see another builder’s take on LP Legacy Premium Sub-Flooring.

How Can Builders Be Assured Floors Will Be Squeak-Free?

Whether you’re building a one-story family dwelling or multifamily structure, LP Legacy Sub-Flooring can help you construct a squeak-free build. 

In fact, when properly installed with LP Legacy Premium Sub-Flooring assemblies, LP Legacy Premium Sub-Floor Adhesive offers the benefit of a squeak-free lifetime limited warranty, which covers squeaks caused by the panel moving on the shank of the nail, during the life of the structure. 

Be sure to review the complete warranty details for LP Legacy Premium Sub-Floor Adhesive.

Looking for more about LP Legacy Premium Sub-Flooring? Check out installation instructions, our warranty and more product information.

LP® TopNotch® 350 Sub-Flooring, which boasts a 50-year limited warranty, is another great option for sub-flooring. LP Legacy adhesive can be used with this type of sub-flooring, and the pairing adds a lifetime limited warranty for squeaks to your build. Check out more details about sub-flooring options here.