Plastic Composite Decking Safety and Performance Requirements
Overview of U.S. building codes and standards
15 February 2022
Composite decking materials are a popular choice today for homeowners and builders alike, in part because the spike in lumber prices due to supply chain shortages caused by COVID-19 has made the cost of wood more comparable to the traditionally more expensive composite lumbers, as well as the desire by consumers to use more sustainable products in and around their homes. As a result, the composite decking industry was estimated to be $1 billion in the U.S. in 2021, representing almost one-third of the global market.
As decking products and materials have evolved, how the standards that regulate these products are addressed and evaluated has evolved as well. In this blog, we'll discuss what constitutes a plastic composite decking product and highlight the U.S. building codes and standards that regulate these products.
The International Building Code (IBC) defines a plastic composite as a generic designation that refers to wood/plastic composites, plastic lumber, and similar materials.
Building codes are the government's laws for regulation of building construction. Building codes are enacted by individual states through legislation, with states commonly allowing for adoption and modification of state codes by lower jurisdictions, typically major cities like Los Angeles, New York, and Chicago. These codes establish minimum requirements, but architects and building owners can require anything they want, and project specifications can require more than the minimum.
State building codes are based on model codes developed by the International Code Council (in the U.S.), the IBC, and International Residential Code (IRC). States can adopt/enact model codes in whole or in part, and may modify depending on the specific needs of state, for example in Florida wind loads are a concern, while in California codes designed to protect structures in the event of an earthquake are necessary.
Then we have referenced standards, which are published standards that include specifications and test methods that become a part of the building code by reference. Referenced standards only become part of the code within context of how they are referenced. For example, a provision that says wind load resistance shall be established will reference the wind load standard, but only for determination of wind resistance. If there is a conflict between the building code and referenced standards, the building code will govern.
Building Codes for Plastic Composite Decking
Code requirements are specific to the material used in decking products. For plastic composite decking, these include IBC Chapter 26 (2612 Plastic Composites) and IRC R507 Exterior Decks (R507.2.2 Plastic composite deck boards, stair treads, guards or handrails). ASTM D 7032 is the Standard Specification for Establishing Performance Ratings for Wood-Plastic Composite and Plastic Lumber Deck Boards, Stair Treads, Guards, and Handrails that outlines testing requirements. Certification is also required for these products (also referred to as listing and labeling).
IBC Chapter 26 and IRC R507 both apply to deck boards, stair treads, handrails, and guards, and evaluate structural performance (span/load rating), end-use factors (temperature and moisture effects), durability (weathering), and termite and decay resistance.
ASTM D 7032 outlines general testing requirements for composite decking materials, including end-use factors, biodeterioration, and surface burning characteristics. Deck board testing includes flexural performance, allowable load with end-use adjustment factors, concentrated load for stair tread, creep recovery, and fastener tests. Guard performance tests include load testing, loading sequence, and fastener assembly tests.
Ongoing Quality Control
It's important that composite decking products are manufactured under an approved quality control system. Ongoing quality control tests are essential to verify that critical properties are maintained and consistent with the originally tested product. In addition, periodic, unannounced inspections by the certification body and periodic verification testing by certification body contribute to a thorough quality control system.