Modern Building Codes: Keeping Pace with the Wood Revolution
In addition to the sprinkler and open frontage increases, a designer's options also include increasing to a higher type of construction, which might include the use of fire-resistive construction throughout the building, fire retardant-treated lumber for exterior walls, or heavy timber construction.
Rated assemblies. There are several types of fire-resistive assemblies and components within a building. These include: vertical assemblies (walls), horizontal assemblies (floors and roofs) and structural frame members (columns and beams). In most cases, these assemblies are required to have either a 1- or 2-hour fire-resistive rating. Fire-resistive construction is typically designated as the number of hours a representative test assembly will resist a standardized fire exposure when tested in a laboratory. One of the standards used for measuring fire resistance of building assemblies is ASTM Test Method E-119, Standard Test Methods for Fire Tests of Building Construction and Materials.
The fire resistance of wood assemblies may be calculated using the provisions of Section 722.6 of the IBC, which is based on the known fire resistance of many tested assemblies. The assemblies in this Section are limited to 1 hour; however, the IBC also references Chapter 16 of the NDS, which has a broader application for calculating fire resistance of exposed wood members. By designing a building to meet the provisions of Type III Construction rather than Type V, the designer is able to take advantage of greater allowable heights and areas. For example, fire retardant-treated wood (referenced in IBC Section 2303.2) is permitted in different locations in different types of construction, as noted in Sections 602.3 and 602.4.2. In Type III and IV Construction, this includes exterior walls and interior walls and partitions. In Types I and II Construction, fire retardant-treated wood is allowed in non-bearing partitions, non-bearing exterior walls where a fire-resistive rating is not required, and portions of the roof construction. In Type I Construction, heavy timber roofs are permitted without fire retardant treatment.
Photo: Lawrence Anderson, www.lawrenceanderson.net
MINIMIZING FIRE RISK AND IMPACTS
STELLA
Location: Marina del Rey, California
Architect: DesignARC
Engineer: Taylor & Syfan Consulting Engineers
Size: 650,466 square feet (2 buildings)
Completed: 2013
Regardless of material, building components such as walls, floors and roofs are designed and rigorously tested to ensure they provide the necessary structural performance to allow occupants in a building to escape should fire occur, and for emergency responders to perform their duties. Fire and building safety codes are updated regularly to include new systems, standards and performance requirements, based on testing and evaluation, which continually improve the safety of buildings.
Building fire safety incorporates a combination of passive and active features. A passive fire safety feature may limit the height and area of the building, prescribe the use of fire-rated building elements or provide for adequate means of egress. Active fire safety features are those such as automatic fire detection or suppression systems that provide occupant notification, alarm transmittance and the ability to suppress fire growth until the fire service arrives. Codes are relying increasingly on active systems, since, with proper maintenance and alarm supervision, they have a high degree of reliability.
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