Wood I-Joists

Use this 3 part SimpleSpecs specification template to specify pre-engineered, prefabricated, wood I-joists for floor and roof framing.

What is it?

Wood I-joists, also known as engineered wood I-joists or simply I-joists, are structural components used in building construction. They are engineered products designed to provide strength, stability, and dimensional stability while using less wood compared to traditional solid lumber joists.

Used in residential and commercial construction for floor and roof framing. They offer cost-effective and efficient alternatives to traditional solid lumber joists, providing builders and designers with increased flexibility and reliable structural performance.

Wood I-joists consist of three main components:

• Flanges: The flanges of an I-joist are the top and bottom horizontal members. They are usually made of laminated veneer lumber (LVL) or solid sawn lumber. The flanges provide the primary load-carrying capacity of the I-joist and are responsible for resisting bending and tension forces.

• Web: The web is the vertical member that connects the top and bottom flanges of the I-joist. It is typically made of oriented strand board (OSB) or plywood. The web serves to transfer the shear forces between the flanges and provides stability to the I-joist.

• OSB or Plywood Panel: An OSB or plywood panel is used to cover the top and bottom flanges and create a flat, continuous surface for attaching flooring, roof decking, or other construction elements.

Advantages over traditional solid lumber joists:

• Greater strength and stiffness: The engineered design of I-joists allows them to have a higher strength-to-weight ratio compared to solid lumber, providing increased load-carrying capacity and reducing the need for additional support beams.

• Consistency: I-joists are manufactured under controlled conditions, resulting in consistent dimensions and structural properties. This allows for more precise construction and reduces material waste.

• Longer spans: Due to their structural efficiency, I-joists can span longer distances without requiring additional supports, enabling greater design flexibility and open floor plans.

• Resistance to warping and twisting: The use of engineered wood products in I-joists, such as LVL and OSB, helps minimize the natural defects and inconsistencies found in solid lumber, resulting in improved dimensional stability and reduced warping or twisting.

Notes:

These joists are fabricated in an off-site facility, then transported to the project site for installation. Joists are typically fabricated from dimensional lumber with plywood or steel tubing webs.

Industry Association:

Recommended Manufacturers: 

Related SimpleSpecs™ master specification:

05 31 00 – Steel Decking

06 17 53 – Shop-fabricated wood trusses