ASTM C208-22

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Designation: C208 − 12 (Reapproved 2017) C208 − 22
Standard Specification for
Cellulosic Fiber Insulating Board
This standard is issued under the fixed designation C208; 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.
ε NOTE—Editorially added missing SI conversions in September 2017.
ε NOTE—Editorially corrected Table 1 in November 2019.
1. Scope
1.1 This specification covers the principal cellulosic fiber insulating board types, grades, and sizes. Requirements are specified for
composition, construction, physical properties, tolerances, sampling procedures, and test methods.
1.2 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.
1.3 When the installation or use of thermal insulation materials, accessories, and systems may pose safety or health problems, the
manufacturer shall provide the user appropriate current information regarding any known problems associated with the
recommended use of the company’s products and shall also recommend protective measures to be employed in their safe
utilization. The user shall establish appropriate safety and health practices and determine the applicability of regulatory
requirements prior to use.
1.4 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.
2. Referenced Documents
2.1 ASTM Standards:
C165 Test Method for Measuring Compressive Properties of Thermal Insulations
C168 Terminology Relating to Thermal Insulation
C209 Test Methods for Cellulosic Fiber Insulating Board
C390 Practice for Sampling and Acceptance of Thermal Insulation Lots
C846 Practice for Application of Cellulosic Fiber Insulating Board for Wall Sheathing
D1037 Test Methods for Evaluating Properties of Wood-Base Fiber and Particle Panel Materials
D1554 Terminology Relating to Wood-Base Fiber and Particle Panel Materials
D2164 Methods of Testing Structural Insulating Roof Deck (Withdrawn 2005)
This specification is under the jurisdiction of ASTM Committee C16 on Thermal Insulation and is the direct responsibility of Subcommittee C16.22 on Organic and
Nonhomogeneous Inorganic Thermal Insulations.
Current edition approved Sept. 1, 2017March 1, 2022. Published December 2017March 2022. Originally approved in 1946 . Last previous edition approved in 20122017
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as C208 – 12.C208 – 12 (2017) . DOI: 10.1520/C0208-12R17E02.10.1520/C0208-22.
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volume information, refer to the standard’s Document Summary page on the ASTM website.
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C208 − 22
TABLE 1 Physical Property Requirements for Cellulosic Fiber Insulating Board
Sound Deadening Roof Insulation Board
Board
Grade 1 Grade 2
Physical
⁄2 in.
7 1 1
⁄16 in. ⁄2 in. 1 in. 2 in. ⁄2 in. 1 in. 2 in.
Requirements
(13 mm)
(11 mm) (13 mm) (25 mm) (51 mm) (13 mm) (25 mm) (51 mm)
thick
thick thick thick thick thick thick thick
Thermal conductivity (k), max, 0.38 0.38 0.38 0.38 0.38 0.50 0.40 0.40
Btu· in./h· ft ·°F (W/m·K) at mean (0.055) (0.055) (0.055) (0.055) (0.055) (0.072) (0.058) (0.058)
temperature of 75± 5°F (24 ± 3°C)
Transverse strength either direction, 12 7 7 14 28 12 24 36
min, lbf (N) (53.4) (31.1) (31.1) (62.3) (124.6) (53.4) (107) (160)
Tensile strength parallel to surface, min, 150 50 50 50 . 150 150 .
B
lbf/in. (kPa) (1034) (345) (345) (345) (1034) (1034)
Tensile strength perpendicular to 600 500 500 500 500 600 600 600
surface, min, lbf/ft (kPa) (28.7) (23.9) (23.9) (23.9) (23.9) (28.7) (28.7) (28.7)
Water absorption by volume, max,% 7 10 10 10 10 7 7 7
Linear expansion, 50–90 % RH, max,% 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5
Flame Spread Index, finish surface, . . . . . . . .
max
Vapor permeance, grains/h·ft ·in. Hg 5 . . . . . . .
pressure differential, (mg/s·m ·kPa) min (0.287)
Modulus of rupture, min, lbf/in. (kPa) 240 140 140 80 40 275 140 70
(1655) (965) (965) (552) (276) (1896) (965) (483)
Deflection at specified min load, max, 0.85 1.25 1.25 0.62 0.31 0.75 0.42 0.21
in. (mm) (22) (32) (32) (16) (8) (19) (11) (5)
2 3
Modulus of Elasticity, min, lbf/in. × 10 . . . . . . . .
F
(mPa)
F
Deflection Span Ratio, max . . . . . . . .
Moisture content by weight, max,% 10 10 10 10 10 10 10 10
G
Racking Load , min plf (N/m) . . . . . . . .
H 2
Compressive Strength , min, lbf/in. . 14.5 14.5 14.5 14.5 15 15 15
(kPa) (100) (100) (100) (100) (105) (105) (105)
E72 Test Methods of Conducting Strength Tests of Panels for Building Construction
2.2 Federal Standard:
4900.1 Rev-1 U.S. Dept. of Housing and Urban Development Minimum Property Standards, One and Two Family Dwellings
3. Terminology
3.1 For definitions of terms used in this specification, see Terminology C168 and Definitions D1554.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 cellulosic fiber insulating board—a fibrous-felted, homogeneous panel made from ligno-cellulosic fibers (usually wood) and
3 3 3 3
having a density of less than 31 lb/ft (497 kg/m ) but more than 10 lb/ft (160 kg/m ).
3.2.1.1 Discussion—
Cellulosic fiber insulating board is characterized by an integral bond which is produced by interfelting of the fibers, but which has
not been consolidated under heat and pressure as a separate stage in manufacture. Other materials may be added during
manufacture to improve certain properties.
4. Classification
4.1 Insulating board covered by this specification consists of six types:
4.1.1 Type I—Sound deadening board, for use in wall assemblies to control sound transmissions.
4.1.2 Type II—Roof insulation board, for use as insulation and cover boards in various roofing systems.
4.1.2.1 Grade 1—Primarily for use under built-up, and modified bitumen roof systems.
4.1.2.2 Grade 2—Primarily for use under single-ply, built-up, and modified bitumen roofing systems.
4.1.3 Type III—Ceiling tiles and panels.
Available from the U.S. Department of Housing and Urban Development, Construction Standards Division, HUD Building, Washington, DC 20410.
C208 − 22
4.1.3.1 Grade 1—Nonacoustical, for use as decorative wall and ceiling coverings.
4.1.3.2 Grade 2—Acoustical, for use as decorative, sound absorbing wall and ceiling coverings.
4.1.4 Type IV—Wall Sheathing.
4.1.4.1 Grade 1—Regular, for use as wall sheathing in frame construction.
4.1.4.2 Grade 2—Structural, for use as wall sheathing in frame construction. When installed in accordance with Practice C846,
structural wall sheathing provides adequate racking resistance for use as exterior wall bracing.
4.1.5 Type V—Backer board, for use behind exterior finish in wall assemblies where there are no structural requirements.
4.1.6 Type VI—Roof deck, for use as roof decking for flat, pitched, or shed-type, open-beamed, ceiling-roof construction.
4.2 On occasion these products are used for other applications. The manufacturer and the purchaser shall agree upon any special
requirements for such end uses.
5. Materials and Manufacture
5.1 Cellulosic fiber insulating board shall be manufactured from refined or partially refined ligno-cellulosic (usually wood) fibers,
by a felting or molding process, into homogeneous panels. Other ingredients may be added to provide or improve certain properties
such as strength and water resistance, in addition to surface finishes for decorative products and special coatings which impart
resistance to flame spread. The material is subjected to such drying temperatures as to effect complete destruction of rot producing
fungi.
5.2 The finished board may be either single or multiple ply. When multiple-ply boards are supplied, a suitable moisture-resistant
adhesive shall be used to join the plies.
6. Physical Properties
6.1 The insulating board shall conform to the physical properties in Table 1.
1 1
6.2 Roof products with a thickness of 1 in., 1Type II roof insulation products may be laminated from multiple plies of ⁄2 in., 2 ⁄2
in. (25 mm, 38 mm, 64 mm), or greater, are post-laminated using thinner board stock whose properties are covered thinner board
stock. For those thicknesses of roof insulation products not listed in Table 1. When laminated, tests shall be performed on the thin
board stock. , and which are laminated from thinner board stock, the thinner board stock shall be tested for conformance to physical
property requirements of the respective thinner board stock’s grade and thickness listed in Table 1.
7. Dimensions, Mass, and Permissible Variations
7.1 The materials covered by this specification are available in the sizes shown in Table 2.
7.2 Length and Width Tolerances—Unless otherwise specified, the tolerance for length and width of any size panel shall
1 3
by + 0, − ⁄16 in. per ft ( + 0, − 5.2 mm ⁄m), but the total tolerance in any dimension sh
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