ASTM E108-20a

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E108 − 20 E108 − 20a An American National Standard
Standard Test Methods for
Fire Tests of Roof Coverings
This standard is issued under the fixed designation E108; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope*
1.1 This fire-test-response standard covers the measurement of the relative fire characteristics of roof coverings exposed to
simulated fire sources originating outside the building. It is applicable to roof coverings intended for installation on either
combustible or noncombustible roof decks when applied as intended for use. The following test methods are included:
1.1.1 Intermittent flame exposure test.
1.1.2 Spread of flame test.
1.1.3 Burning brand test.
1.1.4 Flying brand test.
1.1.5 Rain test.
1.2 Three classes of fire test exposure are described:
1.2.1 Class A Tests are applicable to roof coverings that are expected to be effective against severe fire exposure, afford a high
degree of fire protection to the roof deck, do not slip from position, and are not expected to present a flying brand hazard.
1.2.2 Class B Tests are applicable to roof coverings that are expected to be effective against moderate fire exposure, afford a
moderate degree of fire protection to the roof deck, do not slip from position, and are not expected to present a flying brand hazard.
1.2.3 Class C Tests are applicable to roof coverings that are effective against light fire exposure, afford a light degree of fire
protection to the roof deck, do not slip from position, and are not expected to present a flying brand hazard.
1.3 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only and are not considered standard.
1.4 This standard is used to measure and describe the response of materials, products, or assemblies to heat and flame under
controlled laboratory conditions, but does not by itself incorporate all factors required for fire hazard or fire risk assessment of
the materials, products or assemblies under actual fire conditions.
1.5 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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.6 Fire testing is inherently hazardous. Adequate safeguards for personnel and property shall be employed in conducting these
tests.
1.7 The text of this standard references notes and footnotes that provide explanatory information. These notes and footnotes,
excluding those in tables and figures, shall not be considered as requirements of this standard.
1.8 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
These test methods are under the jurisdiction of ASTM Committee E05 on Fire Standards and are the direct responsibility of Subcommittee E05.14 on External Fire
Exposures.
Current edition approved March 15, 2020April 1, 2020. Published April 2020. Originally approved in 1955. Last previous edition approved in 20172020 as
E108 – 17.E108 – 20. DOI: 10.1520/E0108-20.10.1520/E0108-20A.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E108 − 20a
2. Referenced Documents
2.1 ASTM Standards:
D225 Specification for Asphalt Shingles (Organic Felt) Surfaced With Mineral Granules (Withdrawn 2012)
D226 Specification for Asphalt-Saturated Organic Felt Used in Roofing and Waterproofing
D227 Specification for Coal-Tar-Saturated Organic Felt Used in Roofing and Waterproofing
D312 Specification for Asphalt Used in Roofing
D450 Specification for Coal-Tar Pitch Used in Roofing, Dampproofing, and Waterproofing
D1227 Specification for Emulsified Asphalt Used as a Protective Coating for Roofing
D2178 Specification for Asphalt Glass Felt Used in Roofing and Waterproofing
D2626 Specification for Asphalt-Saturated and Coated Organic Felt Base Sheet Used in Roofing
D2898 Practice for Accelerated Weathering of Fire-Retardant-Treated Wood for Fire Testing
D3018 Specification for Class A Asphalt Shingles Surfaced with Mineral Granules
D3158 Specification for Asphalt Saturated and Coated Organic Felt Used in Roofing (Withdrawn 1983)
D3378 Specification for Asphalt-Saturated and Coated Asbestos Felt Base Sheet Used in Roofing (Withdrawn 1985)
D3462 Specification for Asphalt Shingles Made from Glass Felt and Surfaced with Mineral Granules
D4442 Test Methods for Direct Moisture Content Measurement of Wood and Wood-Based Materials
D4444 Test Method for Laboratory Standardization and Calibration of Hand-Held Moisture Meters
2.2 UL Standards:
UL 55A Materials for Built-Up Roof Coverings
UL790 Tests for Fire Resistance of Roof Covering Materials
2.3 NFPA Standards:
NFPA 256 Tests of Roof Coverings (Withdrawn 2008)
2.4 NIST Standards:
Department of Commerce (DOC) Voluntary Product Standard PS-1 Structural Plywood
Department of Commerce (DOC) Voluntary Product Standard PS-2 Performance Standard for Wood-based Structural-use
Panels
3. Terminology
3.1 Definitions:
3.1.1 significant lateral spread—surface flaming beyond 1-ft. from the lead edge, extending outward to both lateral edges of the
test deck assembly or to both inner edges of metal batten strips, if used, along the side edges of the test deck assembly.
3.1.2 sustained flaming—any flaming which continues uninterrupted for 5 seconds or more.
3.1.3 prepared roof covering—products consisting of shingles, tiles, panels or rolled materials that are typically used for steep
slope roof applications which are applied directly to the roof deck (usually with one or more layers of underlayment and with or
without battens) in accordance with installation instructions supplied with the products.
4. Significance and Use
4.1 The test methods described herein are intended to provide a basis for relative comparison of roof coverings. The test
methods include simulated fire exposure to the outside of the roof coverings, and, where applicable, a determination as to whether
the fire performance characteristics of the roof coverings will be adversely affected by prolonged exposure to rain.
4.2 These test methods measure the surface spread of flame and the ability of the roof covering material or system to resist fire
penetration from the exterior to the underside of a roof deck under the conditions of exposure.
4.3 These test methods also provide criteria to determine if the roof covering material will develop flying burning material,
identified as flying brands, when subjected to a 12-mph (5.3-m/s) wind during the simulated fire exposure tests.
4.4 These test methods do not necessarily illustrate the expected performance of roof coverings under all actual fire conditions,
but they do provide a basis for comparing roof covering materials when subjected to fire sources that are described herein.
4.5 These test methods do not provide any basis for determining the fire resistance characteristics when exposed to a fire
originating in the building to which the roofing material is applied.
4.6 The test methods described herein involve calibrating the test equipment using a calibration deck inclined at a slope of 5
in. per horizontal ft (0.416:1). The tests described herein are performed on test decks inclined at slopes up to and including 5 in.
per horizontal ft. The severity of the test exposure decreases as the slope of the test deck decreases below 5 in. per horizontal ft.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
Available from Underwriters Laboratories Inc., 333 Pfingsten Road, Northbrook, IL 60062.
Available from National Fire Protection Assoc., 1 Batterymarch Park, Quincy, MA 02269.
E108 − 20a
5. Apparatus and Calibration
5.1 The essential elements of the fire test apparatus used for tests described in Sections 8-11 are illustrated in Fig. 1. They consist
of the following:
(a) A test deck to which the roof-covering materials to be tested are applied, mounted on a framework. The incline of the
framework is to be adjustable with respect to incline (slope) as well as the vertical position for fire testing decks with insulated
roof coverings.
(b) A construction of noncombustible boards, mounted on the front of the framework to simulate eaves and cornices.
(c) A gas burner (for intermittent-flame, spread-of-flame and flying brand tests) consisting of a 44-in. (1.12 m) length of
nominal 2 in. (2.38 in./60.3 mm OD) pipe having a ⁄2-in. (12.7 mm) wide, 36-in. (0.91 m) long slot in the side toward the test
deck. The burner is to be supplied with gas at both ends through nominal 1-in. (1.32 in./33.4 mm OD) pipe to provide uniform
gas pressure at the burner assembly.
(d) A blower and air duct for providing the required wind conditions.
(e) Adjustable fins mounted inside the air duct to straighten the air stream and reduce turbulence.
(f) A baffle mounted on the back edge of the test deck to prevent backfiring under the deck.
(g) Noncombustible boards extended from the sides and bottom of the air duct to the simulated-eaves-and-cornices
construction mentioned in (b) (not used during burning brand).
(h) Fire calibration exposure pattern (see 5.5.5).
5.1.1 During the test:
5.1.1.1 Provide free outlet to outside air beyond and above the test apparatus to exhaust air introduced into the test room by the
blower, and
5.1.1.2 Close all openings into the test room other than those mentioned in 5.1.1, such as doors and windows.
5.2 The temperature of the air supplied by the blower shall be maintained between 50 and 90°F (10 and 32°C).
(See Appendix X1 for metric equivalents.)
FIG. 1 Schematic Drawing of Fire Test Apparatus
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5.3 Fig. 2 illustrates an example of the essential elements of a rain test apparatus.
5.4 Calibrating Air Current:
5.4.1 Set up the test apparatus for the intermittent flame test and position a bare 3-ft, 4-in. by 4-ft, 4 in. (1 m by 1.3 m) plywood,
gypsum board or fiber cement board calibration deck on the framework at an incline of 5 in. per horizontal ft (0.416:1).
5.4.2 Measure the air velocity midway up the slope of the calibration deck at its center and 3 in. (76 mm) from each edge.
NOTE 1—Any direct reading instrument with scale graduated in increments of not more than 20 ft/min (6 m/min) or any timed instrument with scale
graduated (for a 1 min timed reading) in increments of not more than 5 ft/min (1.5 m/min) will be suitable.
5.4.3 Position the center of the air measuring device at a nominal 3 ⁄16 in. (94 mm) above the surface. The air flow through
and around the instrument shall be as free and undisturbed as possible.
5.4.4 Adjust the air supply system to produce a 1 min timed average velocity of 1056 6 44 ft/min corresponding to 12 6 0.5
mph (5.3 6 0.2 m/s) at each of the three locations detailed in 5.4.2. In order to comply with 5.5.5, it shall be permitted to adjust
the 1-min time averaged velocity at each location by 65 % from the initial value within the range 1012 to 1100 ft/min (5.1 to 5.5
m/s). This deviation in an individual 1-min timed average velocity shall only be permitted when the average of the 1-min timed
average velocity of all three locations is 12 6 0.5 mph (5.3 6 0.2 m/s).
5.5 Calibrating Flame Temperature:
5.5.1 Following the calibration of the air current described in 5.4, position a fiber cement board calibration deck, 4 ft, 4 in. (1.3
m) long on the framework at an incline of 5 in. per horizontal ft (0.416:1).
5.5.2 Measure the temperature with a No. 14 B & S gauge (1.63 mm) Type K wire thermocouple located 1 in. (25 mm) above
the surface and ⁄2 in. (13 mm) toward the source of the flame from the lower front edge of the calibration deck.
5.5.3 Adjust the gas flow to produce a 2 min average flame temperature of 1400 6 50°F (760 6 28°C) for Classes A and B
and 1300 6 50°F (704 6 28°C) for Class C tests. Allow the response of the thermocouple to the test flame to stabilize before the
2 min average flame temperature is measured. Base the 2 min average on temperatures recorded at 10 s intervals.
5.5.4 Position the top surface of the leading edge of the calibration deck or the test sample flush with the top edge of the
simulated eave within a tolerance of − 0 + ⁄2 in. (13 mm).
5.5.5 When these calibration conditions are met, the flame shall be approximately 3 ft (0.9 m) wide at the bottom edge and in
the center of the width of the calibration deck and the flame shall gradually narrow to approximately a 6 in. (0.15 m) width in the
center of and at the top edge of the calibration deck. This described fire exposure pattern applied to the deck during flame
calibration is shown in Fig. 1, Item h. Intermittent flashes of flame extending another 1 to 2 ft (0.3 to 0.6 m) beyond the top edge
of the calibration deck shall be permitted.
5.6 Rain Test Calibration:
5.6.1 Measure the horizontal projected area over which each nozzle discharges water to the nearest square foot (square metre).
Measure the discharge of water for each nozzle for 1 min.
FIG. 2 Rain Test Apparatus
E108 − 20a
5.6.2 Monitor the total water use during the test (a commercial water meter is suitable for this purpose). For a four day cycle
2 2 2
the water usage shall be 42 6 1 gal/ft (1711 6 41 L/m ). For a seven day cycle the water usage shall be 73 6 1.7 gal/ft (2975
6 71 L/m ).
5.7 Frequency of Calibration:
5.7.1 Calibrate the apparatus for air velocity and flame temperature prior to each day’s use. Calibrate the apparatus for flame
temperature when shifting from Class A or B to Class C tests or vice versa.
5.7.2 Any indication of off-limit condition such as unusual flame appearance or flame contour, excess turbulence, or unusual
noise shall be cause for calibration prior to further use.
5.7.3 For the Rain Test, visually check the water flow from each nozzle (for obvious water obstruction in the nozzle and uneven
spray pattern) each day during the water cycle and make adjustments when necessary.
5.7.4 For the Rain Test, review the total water flow at the end of each day and at the end of each water cycle. Correct the cause
of any off-limit conditions.
6. Preparation of Test Specimens
6.1 Construction of Test Decks:
6.1.1 The test deck for the intermittent flame exposure, burning brand tests, flying brand test, and rain test, except as specified
in the following paragraphs, shall be 3 ft-4 in. (1.0 m) wide by 4 ft-4 in. (1.3 m) long and shall be made of No. 1 white pine lumber
with not less than 8 % nor more than 12 % moisture content. The lumber shall be free of large or loose knots, sapwood, rot, or
pitch pockets, and shall contain no edge knots. Individual deck boards shall be of nominal 1 by 8-in. lumber (S4S). Lay the boards
across the shorter dimension of the test deck space ⁄4 in. (6 mm) apart and securely nail to two nominal 2 by 4-in. wood battens
located under and flush with the outer edges of the deck (Fig. 3). Decks so constructed shall be even and uniform.
6.1.2 Where the roof covering is intended to be installed over other than solid deck, construct the test decks of nominal 1 by
4-in. lumber (S4S) spaced a minimum of 1 ⁄8 in. (41 mm) apart and securely nailed to two nominal 2 by 4-in. wood battens. The
lumber shall be of the same quality as specified in 6.1.1.
FIG. 3 Construction of Test Decks
E108 − 20a
6.1.3 Roof coverings are permitted to be applied to other test decks of the minimum thickness recommended by the
manufacturer. This deviation shall be noted in the report. Plywood, if used, shall be exterior Type A-C grade with face and back
veneers of Douglas fir conforming to PS1 for softwood plywood and shall be identified as a Group 1 species. Oriented Strand
Board (OSB), if used, shall be marked as conforming to PS2. These decks shall have ⁄8-in. (3.2-mm) vertical and horizontal joints
located as specified in 6.1.1 with all vertical joints centered on nominal 2 by 4-in. wood battens. If wood battens or tongue and
groove joints are specified for horizontal joints, this shall be so noted in reporting the tests. The decks for intermittent flame tests
1 1
shall have a ⁄8 in. (3.2 mm) metric horizontal joint 8 in. (203 mm) from and parallel to the 3 ⁄3 ft (1.0 m) long leading edge. In
addition, provide a ⁄8 in. (3.2 mm) metric vertical joint centered on the deck and extending from the leading edge of the deck to
1 1
the ⁄8 in. (3.2 mm) metric horizontal joint. Since the lower 1 ⁄2 in. (38 mm) of this joint is not protected by the 2 by 4-in. batten,
due to the mounting arrangement on the carriage, cover the underside of this joint from the end of the two-by-four to the leading
edge of the deck by a piece of sheet steel, 2 in. (51 mm) wide.
6.1.4 For Classes A and B burning brand tests on decks other than 1 by 8-in. metric nominal lumber, the ⁄8 in. (3.2 mm)
1 1
horizontal joint shall be 22 ⁄2 in. (572 mm) from and parallel to the leading edge of the deck. Class A test decks shall have a ⁄8
in. (3.2 mm) metric vertical joint centered on the deck that extends above the horizontal joint. For Class B test decks, provide two
⁄8 in. (3.2 mm) metric vertical joints, extending above the horizontal joint with each vertical joint located 10 in. (254 mm) from
and parallel to the edge of the deck. For Class C burning brand test, provide five evenly spaced horizontal joints, with a minimum
width of ⁄8 in. (3.2 mm) metric between joints in the plywood.
6.1.5 For the spread of flame test, construct the test deck in the same manner as specified for the intermittent flame test, except
that (1) the vertical and horizontal joints need not be provided, (2) the length of the deck shall be as specified in 6.1.6 and (3)
15/32-in. (12-mm) thick plywood, conforming to PSI-95, is an acceptable deck for materials or systems when minimal
discoloration, without char or no involvement of the plywood test deck occurs, during fire tests. For tests on materials intended
for use only on noncombustible decks, a noncombustible deck of the applicable length specified in 6.1.6 is permitted.
6.1.6 The length of the test deck shall be 13 ft (4.0 m) for Class C tests, 9 ft (2.7 m) minimum for Class B tests, and 8 ft (2.4
m) minimum for Class A tests.
6.2 Application of Roofing on Test Roof Deck—Apply representative samples of roof covering materials for Class B or C tests
to 14 test decks (two each for the intermittent flame, spread of flame, and flying brand tests, four for the burning brand test, and
six for the rain test). Apply representative samples of roof covering materials for Class A tests to 16 test decks (two each for
intermittent flame, spread of flame, and flying brand tests, four for the burning brand test and six for the rain test). Apply the roof
covering materials under investigation in accordance with the manufacturer’s instructions and extend to and flush with the side and
back edges of the deck. At the leading edge the material is to be positioned such that there is minimum coverage or a minimum
number of layers over the horizontal deck joints. It is permitted to provide an air-seal along the sides of the representative sample
of the roof covering material system to restrict air flow under the system during the fire test. The use of a 1-in. (25-mm) maximum
width metal batten strip fastened on top of and along each lengthwise side edge is permitted for mechanically attached single-ply
membrane roof covering systems.
NOTE 2—A practice used to provide an air-seal for mechanically attached, fully-adhered and partially-adhered flexible single-ply membrane systems
is to pull the membrane taut over all four edges of the assembly to fit snugly against the deck and secure it to the wood supports of the test deck.
6.3 Storage and Conditioning of Test Specimens:
6.3.1 Pieces of any hygroscopic materials from the same stock from which the test deck was constructed shall be tacked to the
assembly during construction in such a manner that they are easily removed. These pieces shall be conditioned with the completed
assemblies as described in 6.3.2.
6.3.2 The completed test assembles are to be stored indoors at temperatures not lower than 60°F (16°C) nor higher than 90°F
(32°C) for the period of time necessary to cure the assembly components. Test decks are to be stored so that each will be
surrounded by freely circulating air.
6.3.3 Just before the deck is tested the pieces of hygroscopic materials prepared in 6.3.1 shall be tested for moisture content.
6.3.3.1 Make the moisture determination on two samples from each piece and report the average. For lumber and other
wood-based materials, use Test Methods D4442. Use of an appropriately calibrated moisture meter, as described in Test Methods
D4444, to determine the moisture content of wood or wood products is also permitted. For other hygroscopic materials, use test
methods appropriate for those materials.
6.3.3.2 For lumber, the moisture content shall not be less than 8 % nor more than 12 %. For plywood or OSB, the moisture
content shall not exceed 8 %. For other hygroscopic materials, the moisture shall be within ranges specified by the manufacturer
before the assembly is constructed. These specified ranges shall be typical for exposure at 77 6 9°F (25 6 5°C) and 55 6 10 %
relative humidity. If there is any indication that the lumber, plywood, or other hygroscopic materials have moisture contents outside
these ranges, measure moisture content and replace any out of range materials before building test decks. Out of range pieces shall
be dried or rewetted using methods that do not damage the materials.
6.4 The flying brand tests are required when there is a possibility that the roof covering will break into pieces of flying, flaming
brands or particles which continue to glow after reaching the floor of the test facility. See Appendix Appendix X3.
E108 − 20a
7. Tests—General
7.1 When a roof covering is restricted for use on noncombustible decks, only the spread of flame test is required. Materials
intended for use only on noncombustible decks are permitted to be tested when applied to a noncombustible deck or any type of
combustible deck of the length specified for the spread of flame test.
7.2 When a roof covering is not restricted for use on noncombustible decks, the spread of flame, intermittent flame, and burning
brand tests are required.
7.3 The rain tests are required whenever the fire-retardant characteristics of the roof covering materials or construction has the
potential to be adversely affected by water. See Appendix X2.
7.4 The weathering tests are required for wood shakes and shingles or when the fire-retardant characteristics of the roof covering
materials or construction has the potential to be adversely affected by weathering outdoors.
7.5 The flying brand tests are required when there is a possibility that the roof covering will break into pieces of flaming
particles that support combustion on the floor. See Appendix X3.
7.6 In all of the fire tests described in Sections 8 – 12, trowel noncombustible mortar into the joint formed by the leading edge
of the roof covering material and the framework of the carriage. This is to prevent air or the test flame from traveling under the
material being tested.
7.7 In these tests subject all decks to an air current as calibrated in 5.4.
7.8 Test prepared roof coverings at a slope of 5 in. per horizontal ft (416 mm per horizontal m). Test roof covering systems at
the maximum slope specified by the manufacturer but not to exceed 5 in. per horizontal ft (416 mm per horizontal m). Note the
slope used in the report.
8. Intermittent Flame Exposure Test
8.1 A minimum of two test decks must be tested and passed in sequence.
8.2 Mount a test deck 4 ft-4 in. (1.3 m) long on the framework at the required incline and maintain the calibrated air supply
to produce the specified air current. Subject the test deck to a luminous gas flame and profile as calibrated in 5.5.
8.3 Apply the flame intermittently for specified periods with specified time intervals between applications as follows:
Flame On, Flame Off, No. of Test
Method of Test min min Cycles
Class A 2 2 15
Class B 2 2 8
Class C 1 2 3
8.4 Maintain the air current throughout the test and after the last application of flame until all evidence of flame, glow, and
smoke has disappeared from both the exposed surface of the material being tested and the underside of the test deck, or until failure
occurs, but in no case is the air current or test duration to be maintained for more than 1 h after the last flame cycle for a Class
A or B test or ⁄2 h after the last flame cycle for a Class C test.
8.5 During the intermittent flame test, including on and off periods of flame application, observe for the appearance of sustained
flaming on the underside of the test deck, production of flaming or glowing brands displacement of portions of the test sample,
and exposure or falling away of portions of the roof deck.
9. Spread of Flame Test
9.1 A minimum of two test decks must be tested and passed in sequence.
9.2 Mount a test deck long enough for the desired Class A, B, or C rating in 6.1.6 in the same manner and use a luminous gas
flame as described in 8.2.
9.3 For Classes A and B tests, apply the gas flame and air current continuously for 10 min or until the flame (actual flaming
of the material being tested) permanently recedes from a point of maximum spread, whichever is shorter. For Class C test, apply
the gas flame and air current for a period of 4 min.
9.4 During the application of the test flame, observe the test sample for the distance to which flaming of the material has spread,
production of flaming or glowing brands, and displacement of portions of the test sample.
10. Burning Brand Test
10.1 A minimum of four test decks for Class A fire test exposure and two test decks for Class B or C fire test exposure must
be tested and passed in sequence.
E108 − 20a
10.2 Mount a 4 ft-4 in. (1.3 m) long test deck on the framework at the required incline and maintain the calibrated air supply
to produce the specified air current in the same manner as described in 8.2 for the intermittent flame test, except that the framework
shall be 60 in. (1524 mm) from the air duct outlet (see Fig. 1), and the gas piping and burner are removed so as not to obstruct
the air flow.
10.3 Size and Construction of Brands—Construct the brands (Fig. 4), as follows, and condition in an oven at 105 to 120°F (41
to 49°C) for at least 24 h.
10.3.1 The Class A test brand shall consist of a grid 12 in. (305 mm) square and approximately 2 ⁄4 in. (57 mm) thick made of
dry Douglas fir lumber free of knots and pitch pockets. Use 36 nominal 1 by 1 by 12 in. (25 by 25 by 305 mm) strips, dressed
3 3 1
on all four sides to ⁄4 by ⁄4 in. (19 by 19 mm), and placed in three layers of twelve strips each with strips spaced ⁄4 in. (6.35 mm)
apart. Place these strips at right angles to those in adjoining layers and nail at each end of each strip on one face and in a diagonal
pattern (Fig. 4) on the other face. The dry weight of the finished brand shall be 2000 6 150 g at the time of test.
10.3.2 The Class B test brand shall consist of a grid 6 in. (152 mm) square and approximately 2 ⁄4 in. (57 mm) thick made of
dry Douglas fir lumber free of knots and pitch pockets. Use 18 nominal 1 by 1 by 6 in. (25 by 25 by 152 mm) strips, dressed on
3 3 1
all four faces to ⁄4 by ⁄4 in. (19 by 19 mm), and placed in three layers of six strips each with strips spaced ⁄4 in. (6.35 mm) apart.
Place the strips at right angles to those in adjoining layers and nail at each end of each strip on one face and in a diagonal pattern
(Fig. 4) on the other face. The dry weight of the finished brand shall be 500 6 50 g at the time of test.
10.3.3 Nails used in the construction of Classes A and B brands are No. 16, 1 ⁄2 in. (38 mm) long bright, flat head, diamond
point, wire nails. Sixty-eight nails weighing approximately 42 g are used for Class A brand, and 32 nails weighing approximately
21 g are used for the Class B brand.
10.3.4 The Class C test brand shall consist of a piece of dry nonresinous whit
...