ASTM D6841-03
(Practice)Standard Practice for Calculating Design Value Treatment Adjustment Factors for Fire-Retardant-Treated Lumber
Standard Practice for Calculating Design Value Treatment Adjustment Factors for Fire-Retardant-Treated Lumber
SIGNIFICANCE AND USE
Fire-retardant-treatments are used to reduce the flame-spread characteristics of wood. Chemicals and redrying conditions employed in treatments are known to modify the strength properties of the wood product being treated. This practice gives procedures for fire-retardant chemical manufacturers to use to calculate the effects of their treatment on lumber used in normal and elevated temperature service conditions.
The effect of fire-retardant treatments on the strength of lumber used in roof framing applications is time related. In this practice, the cumulative effect on strength of annual thermal loads from all temperature bins is increased 50 times to establish treatment adjustment factors for fire-retardant treated lumber roof framing.
The procedures of Test Method D 5664 employ an elevated temperature intended to produce strength losses in a short period of time. Although the exposure is much more severe than that which occurs in an actual roof system, the chemical reactions that occur in the laboratory test are considered to be the same as those occurring over long periods of time in the field.
Treatment adjustment factors developed under this practice apply to lumber installed in accordance with construction practices recommended by the fire-retardant chemical manufacturer which include avoidance of direct wetting, precipitation or frequent condensation. Application of this practice is limited to roof applications with design consistent with 1.3.
SCOPE
1.1 This practice covers procedures for calculating treatment adjustment factors to be applied to design values for fire-retardant-treated lumber used at ambient temperatures [service temperatures up to 100—F (38—C)] and as framing in roof systems.
1.2 These design value treatment adjustment factors for the properties of extreme fiber in bending, tension parallel to grain, compression parallel to grain, horizontal shear and modulus of elasticity are based on the results of strength tests of matched treated and untreated small clear wood specimens after conditioning at nominal room temperatures [72°F (22°C)] and of other similar specimens after exposure at 150°F (66°C). The test data are developed in accordance with Test Method D 5664. Guidelines are provided for establishing adjustment factors for the property of compression perpendicular to grain and for connection design values.
1.3 Treatment adjustment factors for roof framing applications are based on computer generated thermal load profiles for normal wood roof construction used in a variety of climates as defined by weather tapes of the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (ASHRAE). The solar loads, moisture conditions, ventilation rates and other parameters used in the computer model were selected to represent typical sloped roof designs. The thermal loads in this practice are applicable to roof slopes of 3 in 12 or steeper, to roofs designed with vent areas and vent locations conforming to national standards of practice and to designs in which the bottom side of the roof sheathing is exposed to ventilation air. For designs that do not have one or more of these base-line features, the applicability of this practice needs to be documented by the user.
1.4 The procedures of this practice parallel those given in Practice D 6305. General references and commentary in Practice D 6305 are also applicable to this practice.
1.5 This practice is written in inch-pound units with SI units provided in parentheses for information only.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
General Information
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Standards Content (Sample)
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Designation: D 6841 – 03
Standard Practice for
Calculating Design Value Treatment Adjustment Factors for
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Fire-Retardant-Treated Lumber
This standard is issued under the fixed designation D6841; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 1.6 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 This practice covers procedures for calculating treat-
responsibility of the user of this standard to establish appro-
ment adjustment factors to be applied to design values for
priate safety and health practices and determine the applica-
fire-retardant-treated lumber used at ambient temperatures
bility of regulatory limitations prior to use.
[service temperatures up to 100°F (38°C)] and as framing in
roof systems.
2. Referenced Documents
1.2 These design value treatment adjustment factors for the
2.1 ASTM Standards:
propertiesofextremefiberinbending,tensionparalleltograin,
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D9 Terminology Relating to Wood
compression parallel to grain, horizontal shear and modulus of
D5664 Test Method for Evaluating the Effects of Fire-
elasticity are based on the results of strength tests of matched
Retardant Treatments and Elevated Temperatures on
treated and untreated small clear wood specimens after condi-
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Strength Properties of Fire-Retardant-Treated Lumber
tioning at nominal room temperatures [72°F (22°C)] and of
D6305 Practice for Calculating Bending Strength Design
other similar specimens after exposure at 150°F (66°C). The
Adjustment Factors for Fire-Retardant-Treated Plywood
test data are developed in accordance with Test Method
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Roof Sheathing
D5664. Guidelines are provided for establishing adjustment
factors for the property of compression perpendicular to grain
3. Terminology
and for connection design values.
3.1 Definitions:
1.3 Treatment adjustment factors for roof framing applica-
3.1.1 Definitionsusedinthispracticeareinaccordancewith
tionsarebasedoncomputergeneratedthermalloadprofilesfor
Terminology D9.
normal wood roof construction used in a variety of climates as
3.2 Definitions of Terms Specific to This Standard:
defined by weather tapes of the American Society of Heating,
3.2.1 bin mean temperature—10°F (5.5°C) temperature
Refrigerating and Air-Conditioning Engineers, Inc.
ranges having mean temperatures of 105 (41), 115 (46), 125
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(ASHRAE). The solar loads, moisture conditions, ventilation
(52), 135 (57), 145 (63), 155 (68), 165 (74), 175 (79) and
rates and other parameters used in the computer model were
185°F (85°C).
selected to represent typical sloped roof designs. The thermal
3.2.2 thermal load profile—the cumulative time per year in
loads in this practice are applicable to roof slopes of 3 in 12 or
each 10°F (5.5°C) temperature bin.
steeper, to roofs designed with vent areas and vent locations
conforming to national standards of practice and to designs in
4. Summary of Practice
which the bottom side of the roof sheathing is exposed to
4.1 Test results developed in accordance with Test Method
ventilation air. For designs that do not have one or more of
D5664 are used in conjunction with computer generated
these base-line features, the applicability of this practice needs
thermal load profiles to calculate treatment factors that are
to be documented by the user.
applied to published design values for untreated lumber.These
1.4 The procedures of this practice parallel those given in
treatmentadjustmentfactorsaccountforthecombinedeffectof
Practice D6305. General references and commentary in Prac-
fire-retardant-treatment and service temperatures.
tice D6305 are also applicable to this practice.
1.5 Thispracticeiswrittenininch-poundunitswithSIunits
5. Significance and Use
provided in parentheses for information only.
5.1 Fire-retardant-treatments are used to reduce the flame-
spread characteristics of wood. Chemicals and redrying condi-
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This practice is under the jurisdiction ofASTM Committee D07 on Wood and
tionsemployedintreatmentsareknowntomodifythestrength
is the direct responsibility of Subcommittee D07.07 on Fire Performance of Wood.
properties of the wood product being treated. This practice
Current edition approved April 10, 2003. Published June 2003. Originally
approved in 2002. Last previous edition approved in 2002 as D6841-02.
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American Society of Heating, Refrigerating, and Air-Conditioning Engineers,
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Inc. (ASHRAE), 1791 Tullie Circle, NE, Atlanta, GA 30329. Annual Book of ASTM Standards, Vol 04.10.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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