BC EWP | I-Joist 101

What Are I-Joists?

I-joists are structural engineered wood products used for framing floors and roofs. The consistency allows for solid performance and smooth ceilings.

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Like all joists, I-joists are typically used to transfer loads to beams, walls, and the foundation. Unlike traditional dimension lumber, which can twist, split, and bow, I-joists offer better consistency and strength while weighing less and being easier to handle. These attributes make I-joists popular with builders of single-family homes, as well as light commercial and multi-family structures.

What Are the Benefits of I-Joists?

I-joists have become a construction industry standard largely because they offer reliable strength, consistency, and engineered performance that can provide a better value than dimension lumber. But that&#;s just the start of their benefits.

More Strength: Thanks to their unique construction, some I-joists, including Boise Cascade® I-Joists, are 20 percent stronger than comparably sized dimension lumber.

Longer Lengths: I-joists can be used to create long spans with less blocking to install faster. Something that dimension lumber simply can&#;t match.

Easier Handling: Dimensional lumber can be heavy and difficult to handle, but I-joists are lightweight, helping to reduce labor hours and labor costs.

Adaptable on the Jobsite: Most I-joists come with pre-stamped knockouts for wires, and allow for larger holes to be cut out of the web for mechanicals and can have very little change in performance. This makes running HVAC, electrical, and plumbing much faster and simpler.

Faster Installation: I-joists can be quickly trimmed in the field and offer a wider nailing surface for speedy installation.

Always Consistent: I-joists are engineered and manufactured for reliability &#; you&#;ll receive the same carefully made, consistently performing, and professionally inspected product time after time.

Sustainably Made: A typical I-joist uses only about half the wood of dimension lumber. The raw materials used in the manufacture of BCI and AJS I-joists are sourced from sustainable and responsibly managed forests. Boise Cascade strives to maximize the use and minimize the waste of each log procured. Bark and material residuals are used for carbon-neutral biomass fuel to generate over 70% of the energy needed to manufacture our products, keeping our emissions and reliance on fossil fuels low.

What Is an I-Joist Used For?

I-joists are a go-to product for residential and multi-family construction projects because they&#;re available in common sizes for today&#;s construction projects. They can also reduce common mistakes and hassles to make: framing simpler, floors flatter, and homes perform to meet customer expectations.

The strength and stability of I-joists make them a popular choice for engineered floors and roof framing. I-joists come in longer spans than dimensional lumber but without the potential defects and imperfections that eat up time and labor at the job site. With less shrinking, twisting, and bowing, the result is simpler floor and roof layouts that perform over time. Their consistency and performance, along with proper design, helps reduce vibrations, which means less bounce, fewer squeaks, and solid, quiet floors.

How Are I-Joists Made?

I-joists consist of OSB web between two flanges, which are typically constructed of dimensional lumber or laminated veneer lumber (LVL) and joined by a durable structural adhesive. BCI® Joists use Versa-Lam® LVL for strength and durability while AJS joists have flanges made of machine stress-rated lumber.

A finished I-joist looks like the letter I, lending the product its name.

What Are Common I-Joists Sizes?

I-Joists are manufactured in a wide range of depths ranging from 9 ½&#;-24&#; and can be special ordered in lengths as long as 60 feet.

BCI Joists are available in standard depths up to 20&#; and AJS joists are available in depths up to 24&#;. The extra depths make an ideal solution for multifamily applications.

How Far Do I-Joists Span?

The answer to this question depends on many factors unique to your project. Download the BCI or AJS I-joist Specifier&#;s guide to see I-joist span chart for your specific application or learn more about the Boise Cascade software suite.

A High-Performance Advantage

I-Joist Basics

I-joists are strong, lightweight, "I" shaped engineered wood structural members that meet demanding performance standards. I-joists are comprised of top and bottom flanges, which resist bending, united with webs, which provide outstanding shear resistance. The flange material is typically laminated veneer lumber (LVL) or solid sawn lumber, and the web is made with plywood or OSB. The robust combination of structural characteristics results in a versatile, economical framing member that is easy to install in residential and light commercial projects.

Common I-Joist Applications

I-joists are used extensively in residential floor and roof framing. They are ideal for long spans, including continuous spans over intermediate supports. Because I-joists are straight and true, it's easier for builders to avoid crowning and maintain a level framing surface. In addition, wood I-joists are typically stocked and readily available in depths that meet the needs of residential framing.

Common Depths

9-1/2", 11-7/8", 14", 16". Flange widths vary from 1-1/2" to 3-1/2"; long lengths are readily available.

Contact us to discuss your requirements of i joist beam. Our experienced sales team can help you identify the options that best suit your needs.

Common Uses

I-joists are popular for floor and roof framing. Many APA member-manufacturers have software design tools; contact the manufacturer (at right) for more information. 

APA PRI-400

APA Performance Rated I-joists (PRIs) are manufactured in accordance with APA PRI-400, Performance Standard for Residential I-joists. This Performance Standard provides an easy-to-use table of allowable spans for applications in residential floor construction, allowing designers and builders to select and use I-joists from various member manufacturers using just one set of span tables. APA PRIs are recognized through ICC-ES ESR-.

The APA Mark of Quality

APA trademarks appear only on products manufactured by APA member mills. The mark signifies that product quality is subject to verification through APA audit&#;a procedure designed to assure manufacture in conformance with APA performance standards or the standard shown in the mark.

I-Joist Publications
 

Includes information on span ratings, installation details, cantilever designs, architectural specifications and engineering design properties for APA Performance Rated I-Joists.

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Resource Library

Access a complete list of APA publications about I-joists in APA's Resource Library.

Fire Protective Assemblies for Wood I-Joist Floors

Learn about several options that enhance the fire performance of I-joist floor systems and comply with the International Residential Code (IRC) by visiting the I-Joist Fire Assemblies page.

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Technical Topics TT-015: Wood I-Joist Floors, Firefighters and Fire

A discussion of the durability and safety of wood I-joist floor assemblies in structure fires. Includes APA&#;s recommendation to increase the fire endurance of all floor-joist assemblies based on the International Building Code.

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Technical Topics TT-126: Applicability Of APA Trademarks On Engineered Wood Products Surface-Coated With Fire Protective Coatings

Contains Q&A concerning fire protective coatings. Certification and inspection of products treated with fire-protective coatings are outside the scope of APA.

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White Paper: Basis of IRC Membrane Protection Provisions

APA, AWC and WIJMA jointly developed this paper that describes the history, background and intent of the IRC provisions for fire protection of floors as well as the methods used for establishing equivalence and compliance with these fire protection requirements.

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White Paper: Code Requirements for Prefabricated Wood I-Joists

APA, AWC and WIJMA jointly developed this paper that describes the basic code recognition for prefabricated wood I-joists and the need for product certification in compliance with the codes.

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White Paper: Fire Protection of I-Joist Floors with Factory-Applied Solutions

APA developed this paper that describes the basic fire protection requirements for prefabricated wood I-joists with factory-applied fire protection solutions for compliance with the codes.

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