Building codes require all building systems to perform to the same level of safety, regardless of material used—and wood-frame construction has a proven safety and performance record for fire protection.
While building materials play only a small part in designing a structure for life safety, ordinary wood-frame construction with plywood or OSB sheathing is readily accepted in the International Building Code (IBC). However, to achieve larger allowable areas, a designer’s options include protected construction, heavy timber construction and fire-retardant-treated construction.
The major source documents for dimension lumber fire-endurance assemblies are the American Forest & Paper Association’s (AF&PA’s) ASD/LRFD Manual for Engineered Wood Construction, Chapter M16, AF&PA’s DCA 3 – Fire Rated Wood Floor and Wall Assemblies, the Fire Resistance Design Manual published by the Gypsum Association, and the Fire Resistance Directory published by Underwriters Laboratories (UL). The major source document for metal plate connected truss fire-endurance assemblies is the Metal Plate Connected Wood Truss Handbook, section 17 Fire Performance of Trusses and section 18 Sound Transmission and Fire Resistance Rated Truss Assemblies, found at www.woodtruss.com.
There are numerous fire-endurance assemblies detailed in these source documents. These assemblies include different options, such as the direct application of gypsum or gypsum used in combination with resilient channels, insulation or suspended ceilings. They range in performance from 45 minutes to two hours, providing flexibility for any project need.
Also important is the fact that some wood products, such as the large beams used in heavy timber construction and cross laminated timber (CLT) may perform better in a fire situation than non-combustible materials. Because they are thick and solid, these products char at a slow and predictable rate. This char protects the wood from further degradation, helping to maintain the building’s structural integrity and reducing its fuel contribution to the fire, which in turn lessens the fire’s heat and flame propagation. Section 602.4 of the 2009 IBC has prescriptive provisions for wood members which meet the definition of heavy timber.
- Designing for Fire Protection – WoodWorks
- ANSI/AF&PA NDS-2005 – National Design Specification® (NDS®) for Wood Construction, Chapter 16 – Fire Design of Wood Members – American Wood Council (AWC)/AF&PA
- ASD/LRFD Manual for Engineered Wood Construction, Chapter M16 – Fire Design – AWC/AF&PA
- Calculating the Fire Resistance of Exposed Wood Members – American Wood Council (AWC)/AF&PA
- Fire-Rated Systems – APA
- Fire Safety: A Wood Frame Building Performance Fact Sheet – FPInnovations and the Canadian Mortgage and Housing Corporation (CMHC)
- Fire Safety Defined – Canadian Wood Council (CWC)
- Technical Topics: Wood I-Joist Floors, Firefighters and Fire – APA
- Wood-frame Construction: Fire Resistance and Sound Transmission – FPInnovations, Société d’habitation du Québec and CMHC
- CAM for Calculating and Demonstrating Assembly Fire Endurance – AWC
- Design of Fire Resistive Exposed Wood Members – AWC
- Fire Design for Code Acceptance – AWC
- Fireblocking and Draftstopping – AWC
- Fire Rated Wood Floor and Wall Assemblies – AWC
- Heat-Resistant Adhesives (HRA) and Finger-Jointed Lumber Fast Facts – Western Wood Products Association