AC07 - Prefabricated Wood I-Joists
ICC-ES Acceptance Criteria for Prefabricated Wood I-Joists
Last updated: September 21, 2025
Overview
Prefabricated wood I-joists are strong, lightweight engineered wood beams shaped like the letter I. They consist of top and bottom flanges made of lumber or laminated veneer lumber and a web made of plywood or oriented strand board. This design allows them to support floors and roofs over long spans with less material than solid wood joists. Building codes require that their structural capacity be proven through standards such as ASTM D5055, ensuring that these I-joists can safely carry the loads in a house or other structure.
Purpose
This acceptance criteria provides a basis for evaluating prefabricated wood I-joists that may not be directly covered by existing codes. It establishes testing protocols, structural performance requirements, and quality standards needed for code approval of these engineered wood products.
Benefits of Compliance
- Nationwide acceptance by building officials for I-joist installations
- Streamlined approval process for engineered wood products
- Third-party verification of structural performance claims
- Enhanced marketability and credibility for I-joist manufacturers
Resources
Frequently Asked Questions
What is a prefabricated wood I-joist?
A prefabricated wood I-joist is an engineered wood beam shaped like the letter I, with top and bottom flanges made of lumber or laminated veneer lumber and a web made of plywood or oriented strand board. They support floors and roofs over long spans with less material than solid wood joists.
Why do I-joists need AC07 evaluation?
Because I-joists are engineered products not covered by traditional lumber grading rules, AC07 evaluation through ICC-ES provides independent verification that they meet structural performance requirements. The resulting ESR gives building officials confidence to approve their use.
What testing standard applies to wood I-joists?
ASTM D5055 is the primary standard for evaluating the structural capacity of prefabricated wood I-joists. AC07 references this standard to ensure I-joists can safely carry the loads expected in residential and commercial structures.
Was this resource helpful?
Your feedback helps us improve our technical resources and guides.