Designation:D6841−21StandardPracticeforCalculatingDesignValueTreatmentAdjustmentFactorsforFire-Retardant-TreatedLumber1ThisstandardisissuedunderthefixeddesignationD6841;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thispracticecoversproceduresforcalculatingadjust-mentfactorsthataccountfortheeffectsoffire-retardanttreatmentondesignpropertiesoflumber.Theadjustmentfactorscalculatedinaccordancewiththispracticearetobeappliedtodesignvaluesforuntreatedlumberinordertodeterminedesignvaluesforfire-retardant-treatedlumberusedatambienttemperatures[servicetemperaturesupto100°F(38°C)]andasframinginroofsystems.NOTE1—Thisanalysisfocusesontherelativeperformanceoftreatedanduntreatedmaterialstestedafterequilibratingtoambientconditionsfollowingacontrolledexposuretospecifiedconditionsofhightempera-tureandhumidity.Elevatedtemperature,moisture,loadduration,andotherfactorstypicallyaccountedforinthedesignofuntreatedlumbermustalsobeconsideredinthedesignoffire-retardant-treatedlumber,butareoutsidethescopeofthetreatmentadjustmentsdevelopedunderthispractice.1.2Theseadjustmentfactorsforthedesignpropertiesinbending,tensionparalleltograin,compressionparalleltograin,horizontalshear,andmodulusofelasticityarebasedontheresultsofstrengthtestsofmatchedtreatedanduntreatedsmallclearwoodspecimensafterconditioningatnominalroomtemperatures[72°F(22°C)]andofothersimilarspecimensafterexposureat150°F(66°C).ThetestdataaredevelopedinaccordancewithTestMethodD5664.Guidelinesareprovidedforestablishingadjustmentfactorsfortheprop-ertyofcompressionperpendiculartograinandforconnectiondesignvalues.1.3Treatmentadjustmentfactorsforroofframingapplica-tionsarebasedonthermalloadprofilesfornormalwoodroofconstructionusedinavarietyofclimatesasdefinedbyweathertapesoftheAmericanSocietyofHeating,Refrigera...
