After a number of years of discussion, agreement has been reached to clarify fire safety testing requirements for Fire Retardant Treated Wood (FRTW), that is wood which is impregnated with fire safety products (usually in a pressure treatment). New wording will be introduced into the IBC, IRC and NFPA 5000 building codes specifying for FRTW panels flame spread < index 25 and flame front progression < 3.2 m (ASTM E84 or UL 723 test) and pressure impregnation at ≥ 50 ppi or specified “other means”. Additionally it is added that the tests must be carried out with a longitudinal gap of 3.2 mm (as when panels are installed side-by-side in construction).
Source: GBH International “Fire Safety & Technology Bulletin” November 2019 https://www.gbhint.com/fire-safety-and-technology-bulletin/