When designing and constructing Multi-Family (MF) wood floors, there are many options for I-joist depths and spacings depending on floor spans and design loads of each project. Our sales experts often receive questions from customers requesting help to determine what product would be appropriate for their project. We’ll cover the best options when designing floors with BCI® or AJS® I-joists.

To provide greater flexibility when designing MF buildings, Boise Cascade® manufactures 18 different BCI and AJS I-joist series, available in three geographical regions in North America. This variety helps allow you to meet specific performance requirements at a price point you’re looking to achieve.

In Multi-Family construction, typically a design live load 40 lbs./sq. ft (psf) is required for living areas, while the dead load on the floor can vary widely from 15 psf to 50 psf or higher depending primarily on the amount of lightweight or gypsum concrete. Keep in mind that floor joist spans for MF wood construction vary but are generally less than 30 feet.

The parameters used for this exercise are: 40 psf live load, 25 psf dead load, 23/32″ APA-rated floor sheathing glued and nailed, two layers of fire-rated gypsum board attached to the bottom flange, L/600 live load deflection limit, and the most restrictive of L/240 or 1″ total load deflection limit. Based on these design parameters, the span lengths shown are the clear distance between supports and the most restrictive of either simple or multiple-span applications.

The table below shows some of the most cost-effective floor BCI and AJS I-joist options for the products available in each region.

Of course, there are additional elements to consider when designing MF wood floors. To further assist you, download one of our specifier guides containing the additional information you need.

Eastern Guide / Western Guide / Eastern Canada / Western Canada

Did you know?

Holes as large as 18″ in diameter or length may be allowed in 24″ AJS I-joists. This allows for HVAC to easily be installed in the floor cavity. BC Calc® software may be used to analyze different web hole shapes and sizes to make sure it doesn’t conflict with the integrity of the BCI or AJS I-joist.

For more information regarding Boise Cascade EWP, contact Jeff Bryce.