Better Floor Performance In Multi-Family Construction

In multi-family construction, the quality of the floor not only affects the structural integrity of the building but also significantly impacts the comfort and satisfaction of its occupants. In recent years, there has been a growing recognition of the need to enhance floor performance criteria to meet evolving architectural designs and occupant expectations.

We know that floor performance is influenced by various factors:

• Joist span, depth, spacing, and continuity
• Sheathing thickness and attachment methods
• The choice of floor covering and topping, such as carpet, poured concrete, or tile, etc.
• The type of ceiling, whether it's a drop ceiling or direct-attached gypsum board, also plays a significant role

Limiting deflection of all floor components (sheathing, joists, supporting members) is crucial in determining floor performance. Per the 2021 International Building Code (IBC®), the maximum deflection of a floor member is limited to L/360 live load deflection and L/240 total load deflection. However, we recommend a more stringent criteria of L/480 live load deflection for our products, representing a 33% increase in floor stiffness compared to the code minimum.

Higher deflection criteria, such as L/600 live load deflection often utilized for commercial purposes, signify a 67% increase compared to code minimum standards. These elevated criteria underscore the industry's commitment to enhancing floor performance beyond regulatory requirements.

Raising The Bar

Boise Cascade® offers solutions to design higher floor performance levels. Software tools like BC Calc® and BC Framer® provide additional optional floor performance checks, allowing adjustments to materials to further improve overall floor performance. BC Calc® allows the designer to utilize the NBCC Vibration criteria for all floor joist designs, minimizing floor movement continuation (i.e: vibration) which can be unsettling to occupants. Additionally, Boise Cascade's BC FloorValue® analysis integrates sheathing, joist, and support deflection to comprehensively evaluate floor systems.

For superior floor performance, it's essential to consider not only regulatory standards but also advancements in technology and best practices. By prioritizing floor criteria, we can ensure safer, more comfortable, and more durable multi-family structures for the benefit of all stakeholders.

For more information on enhanced floor performance criteria and Boise Cascade's offerings, refer to the Eastern Specifier Guide, Page 4, detailing our three-star and four-star deflection criteria. 

For specific joist design with higher performance needs, please feel free to contact Boise Cascade EWP Engineering at 800.232.0788.