New advances in I-joists helping builders slash labor; offer better performance

When it comes to building strong homes, it could be said, “together everything achieves more.”

Builders who construct structural systems, rather than individual components, can optimize material efficiencies, address typical design challenges and improve the overall performance of homes.

This is particularly true for floors. Developing floor structures as integrated systems can help builders create quieter, well performing floors. Properly designed floor systems may reduce the potential for cracks in floor finishes. It is also possible to reduce the amount of columns and interior walls needed for support, while still meeting code requirements.

Advancements

In the three decades since Trus Joist pioneered wood I-joists, the products have became popular with builders for their high strength-to-weight ratio, consistency, dimensional stability, long lengths and ease of use. According to industry associations, approximately 50 percent of new wood-framed homes use prefabricated wood I-joists.

Wood I-joists have evolved over time, and today, manufacturers often use engineered wood components to produce prefabricated wood I-joists. These components include laminated veneer lumber (LVL) flanges and oriented strand board (OSB) webs. Such engineered materials resist warping, twisting and shrinking, yet are strong and easy to work with using standard tools.

In recent years, manufacturers have developed even more efficient ways to make use of wood fiber in their I-joists. In some cases, this allows for greater carrying capacity and longer spans.

Other features offered by some manufactures include pre-cut web knockout holes to eliminate guesswork and extra effort when routing small pipes and wiring. For increased flexibility during construction, many manufacturers permit additional web holes to be drilled to allow for HVAC ductwork and other utility runs as long as users follow published guidelines.

Selecting Wood I-Joists

While wood I-joists work well as part of a floor system with various framing materials, including engineered wood rim board and OSB floor panels, not all I-joists perform at the same level. I-joist performance greatly depends upon I-joist flange grades and OSB web specifications. Other factors that affect overall floor performance include I-joist series and depth, on-center-spacing, span length, deflection criteria, and floor panel thickness. The range of options can make it challenging to balance floor performance with cost.

Fortunately, manufacturers provide software tools that help builders predict a floor system’s overall performance and allow for the consideration of all the variables mentioned above before construction begins. Some building product manufacturers’ software can evaluate a builder’s preferred materials and installation methods and provide a floor performance rating based on those specifications. Such tools can help builders predict how their customers will perceive the performance of the floor structure, while comparing many cost-effective solutions.

Quiet Integrated Floor SystemS

Appropriate planning and installation is essential in a systems approach to designing and constructing floor framing.

To help construct quieter floors, it is important to balance spans and spacing, as well as the size of the joists. A code compliant floor may not perform adequately for many homeowners. I-joist designs that utilize near maximum allowable spans may be more susceptible to annoying vibrations when people walk on the finished floor. For solid, quieter floors, check the manufacturer’s guidelines since span recommendations vary.

Another way to reduce noise is to place a dab of adhesive on the seat of the hanger when fastening I-joists at supports. Since I-joists are typically attached to beams or headers using metal hangers, this helps prevent squeaks caused by the I-joist rubbing on the hanger.

For builders who use I-joists with pre-cut knockout holes or drill their own holes, it is important to size the hole somewhat larger than the pipe or conduit passing through rather than having a snug fit. This helps reduce noise from the joists and pipe rubbing against one another when someone walks across the floor.

Engineered wood I-joists are only one piece of the integrated floor system puzzle, but when properly planned, specified and installed, they can help builders meet code requirements and homeowner expectations.