Since engineered wood products, such as TJI® joists, Microllam®, LVL, Parallam®PSL, and TimberStrand®LSL, are not addressed prescriptively in the code, we rely on our code reports as evidence of acceptability as alternative materials. The following language from the International Residential Code (IRC), permits using alternative materials, including engineered wood products:
IRC Section R104.11 - The provisions of this code are not intended to prevent the installation of any material or to prohibit any design or method of construction not specifically prescribed by this code, provided that any such alternative has been approved. An alternative material, design or method of construction shall be approved where the building official finds that the proposed design is satisfactory and complies with the intent of the provisions of this code, and that the material, method or work offered is, for the purpose intended, at least the equivalent of that prescribed in this code.
To help the building official verify acceptability of alternate materials, the ICC Evaluation Service, Inc. (ICC ES), was established for the purpose of providing an independent and impartial review of alternate materials, designs or methods of construction for compliance with the building codes. ICC-ES provides this verification in accordance with the ASTM standards mentioned below.
Prefabricated wood I-Joists are specifically covered under Section R502.1.2 of the IRC and this section states that "Structural capacities and design provisions for prefabricated wood I-joists shall be established and monitored in accordance with ASTM D 5055." Beginning with the 2015 codes, rim board products are covered under Section R502.1.7 which references ASTM D 7672.
Similar to TJI® Joists, structural composite lumber products (Microllam® LVL, Parallam® PSL, and TimberStrand® LSL) are covered under Section R502.1.5 of the IRC and this section states that "Structural capacities for structural composite lumber shall be established and monitored in accordance with ASTM D 5456."
Weyerhaeuser has established and continues to work with independent 3rd parties to monitor structural capacities and design provisions, as required, for TJI® Joists and Microllam® LVL, Parallam® PSL, and TimberStrand® LSL structural composite lumber product as verified by the reports below.
ICC-ES Evaluation Reports:
Trus Joist® TJI Joists: ESR-1153
Structural Composite Lumber -Trus Joist® TimberStrand® LSL; Microllam® LVL; Parallam® PSL; TimberStrand® LSL Rim Board; TJ Rim Board; and Weyerhaeuser Rim Board: ESR-1387
State of Florida Product Approvals:
Trus Joist® TJI Joists: FL1630-R8
Structural Composite Lumber: FL6527-R7
City of Los Angeles Research Reports:
Trus Joist® TJI Joists: RR-25538
Structural Composite Lumber: RR-25202
Using Weyerhaeuser Products in Conventional Code: Technical Resource Sheet 1502
Engineer's Seal Requirements for I-Joists, Structural Composite Lumber and Plated Trusses: TB-120