Condition
Where fire retardant treated wood (FRTW) is required, a field-applied treatment is proposed which meets the flame spread criteria specified in IBC Section 2303.2.
Question
Can a field-applied treatment of wood qualify it as fire retardant treated wood (FRTW)?
Building Code Sections
2018 IBC 2303.2.
Interpretation
No, a field-applied, post-manufacture treatment of wood does not qualify the wood as fire retardant treated wood (FRTW).
Per the IBC (underlines added):
2303.2 Fire-retardant-treated wood. Fire-retardant-treated wood is any wood product that, when impregnated with chemicals by a pressure process or other means during manufacture, shall have, when tested in accordance with ASTM E84 or UL 723, a listed flame spread index of 25 or less and show no evidence of significant progressive combustion when the test is continued for an additional 20-minute period. Additionally, the flame front shall not progress more than 10 1/2 feet (3200 mm) beyond the centerline of the burners at any time during the test.
2303.2.1 Pressure process. For wood products impregnated with chemicals by a pressure process, the process shall be performed in closed vessels under pressures not less than 50 pounds per square inch gauge (psig) (345 kPa).
2303.2.2 Other means during manufacture. For wood products impregnated with chemicals by other means during manufacture, the treatment shall be an integral part of the manufacturing process of the wood product. The treatment shall provide permanent protection to all surfaces of the wood product. The use of paints, coating, stains or other surface treatments is not an approved method of protection as required in this section.
Per the Code and Commentary: “This section elaborates on the requirements of treatment using other means during manufacture and requires treatment to be an integral part of the manufacturing process.”
Important Notes
Last reviewed: 15 Apr 2022.
This code interpretation is provided to help applicants understand the building codes. It represents the opinion of the Salt Lake City Building Official in relation to a specific project at the time it was rendered. Per International Building Code Section 104.1, such interpretations shall be in compliance with the intent and purpose of the building code, and they shall not have the effect of waiving requirements specifically provided for in the building code. Therefore, do not assume that any interpretation would also apply to your project. Always consult with a Salt Lake City building plans examiner for specific interpretations as needed regarding your project.