ASTM_D_6305_-_21.pdf

Designation:D630521Standard Practice forCalculating Bending Strength Design Adjustment Factorsfor Fire-Retardant-Treated Plywood Roof Sheathing1This standard is issued under the fixed designation D6305;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This practice covers procedures for calculating adjust-ment factors that account for the effects of fire-retardanttreatment on bending strength of plywood roof sheathing.Theadjustment factors calculated in accordance with this practiceare to be applied to design values for untreated plywood inorder to determine design values for fire-retardant-treatedplywood used as sheathing in roof systems.The methodsestablish the effect of treatment based upon matched bendingstrength testing of materials with and without treatment afterexposure at elevated temperatures.NOTE1This analysis focuses on the relative performance of treatedand untreated materials tested after equilibrating to ambient conditionsfollowing a controlled exposure to specified conditions of high tempera-ture and humidity.Elevated temperature,moisture,load duration,andother factors typically accounted for in the design of untreated plywoodmust also be considered in the design of fire-retardant-treated plywoodroof sheathing,but are outside the scope of the treatment adjustmentsdeveloped under this practice.1.2 It is assumed that the procedures will be used forfire-retardant-treated plywood installed using appropriate con-struction practices recommended by the fire retardant chemicalmanufacturers,whichincludeavoidingexposuretoprecipitation,direct wetting,or regular condensation.1.3 This practice uses thermal load profiles reflective ofexposures encountered in normal service conditions in a widevariety of continental United States climates.The heat gains,solar loads,roof slopes,ventilation rates,and other parametersused in this practice were chosen to reflect common sloped roofdesigns.This practice is applicable to roofs of 3 in 12 or steeperslopes,to roofs designed with vent areas and vent locationsconforming to national standards of practice,and to designs inwhich the bottom side of the sheathing is exposed to ventilationair.These conditions may not apply to significantly differentdesigns and therefore this practice may not apply to suchdesigns.1.4 Information and a brief discussion supporting the pro-visions of this practice are in the Commentary in the appendix.A large,more detailed,separate Commentary is also availablefrom ASTM.21.5 The methodology in this practice is not meant to accountfor all reported instances of fire-retardant plywood undergoingpremature heat degradation.1.6 The values stated in inch-pound units are to be regardedas standard.The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.7 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.8 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Referenced Documents2.1 ASTM Standards:3D9 Terminology Relating to Wood and Wood-Based Prod-uctsD5516 Test Method for Evaluating the Flexural Properties ofFire-Retardant Treated Softwood Plywood Exposed toElevated Temperatures3.Terminology3.1 Definitions:3.1.1 Definitions used in this practice are in accordance withTerminology D9.1This practice is under the jurisdiction of ASTM Committee D07 on Wood andis the direct responsibility of Subcommittee D07.07 on Fire Performance of Wood.Current edition approved June 1,2021.Published July 2021.Originally approvedin 1998.Last previous edition approved in 2015 as D6305 08(2015)1.DOI:10.1520/D6305-21.2Commentary on this practice is available from ASTM Headquarters.RequestFile No.D071004.3For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,G