- Fire retardant treatments (FRT) were developed to be applied to building materials, such as dimension lumber (FRTW) and plywood, to reduce the ability of the wood to fuel a fire.
- This treatment can allow FRT materials to be used as an acceptable alternative for building code requirements that specify noncombustible material in specific applications.
- While reducing flammability, FRT may also degrade the structural properties of the wood.
- Trusses designed with FRT lumber may require:
- A reduction in the design values of the wood materials, and/or
- A reduction in the capacity of connectors used
- The following steps describe how to properly design trusses using FRT lumber.
Accredited Product Certification Report
- Obtain the Accredited Product Certification Report for the FRT lumber product
- Make sure the report is from an accredited ISO/IEC 17065 Product Certification Body
- The evaluation report should contain reduction values for lumber and connectors for the FRT product
Apply to Truss Design
- Most truss design software applies FRT lumber and plate reductions to the truss design via a reduction of the lumber and plate DOL values.
- Typical roof DOL * Reduction value = Reduced DOL
- 1.15 * 0.8 = 0.92
- Verify that the reduced DOL has been used for the truss design.