ASTM C11-23

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Designation: C11 − 18b C11 − 23
Standard Terminology Relating to
Gypsum and Related Building Materials and Systems
This standard is issued under the fixed designation C11; 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.
1. Scope*
1.1 This standard covers terminology relating to gypsum and related building materials and systems. The terms are generically
defined. More specific and expanded definitions may appear in appropriate standards.
1.2 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:
C22/C22M Specification for Gypsum
C28/C28M Specification for Gypsum Plasters
C35 Specification for Inorganic Aggregates for Use in Gypsum Plaster
C36/C36M Specification for Gypsum Wallboard (Withdrawn 2004)
C37/C37M Specification for Gypsum Lath (Withdrawn 2004)
C52 Specification for Gypsum Partition Tile Or Block (Withdrawn 1982)
C59/C59M Specification for Gypsum Casting Plaster and Gypsum Molding Plaster
C61/C61M Specification for Gypsum Keene’s Cement
C317/C317M Specification for Gypsum Concrete
C318/C318M Specification for Gypsum Formboard
C472 Test Methods for Physical Testing of Gypsum, Gypsum Plasters, and Gypsum Concrete
C473 Test Methods for Physical Testing of Gypsum Panel Products
C475/C475M Specification for Joint Compound and Joint Tape for Finishing Gypsum Board
C843 Specification for Application of Gypsum Veneer Plaster
C557 Specification for Adhesives for Fastening Gypsum Wallboard to Wood Framing
C587 Specification for Gypsum Veneer Plaster
C588/C588M Specification for Gypsum Base for Veneer Plasters (Withdrawn 2005)
C954 Specification for Steel Drill Screws for the Application of Gypsum Panel Products or Metal Plaster Bases to Steel Studs
from 0.033 in. (0.84 mm) to 0.112 in. (2.84 mm) in Thickness
C1007 Specification for Installation of Load Bearing (Transverse and Axial) Steel Studs and Related Accessories
C1396/C1396M Specification for Gypsum Board
E84 Test Method for Surface Burning Characteristics of Building Materials
This terminology is under the jurisdiction of ASTM Committee C11 on Gypsum and Related Building Materials and Systems and is the direct responsibility of
Subcommittee C11.91 on Terminology and Editorial.
Current edition approved Nov. 1, 2018Jan. 1, 2023. Published November 2018January 2023. Originally approved in 1916. Last previous edition approved in 2018 as
C11 – 18a.C11 – 18b. DOI: 10.1520/C0011-18B.10.1520/C0011-23.
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.
*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
C11 − 23
E96/E96M Test Methods for Gravimetric Determination of Water Vapor Transmission Rate of Materials
E119 Test Methods for Fire Tests of Building Construction and Materials
E337 Test Method for Measuring Humidity with a Psychrometer (the Measurement of Wet- and Dry-Bulb Temperatures)
3. Terminology
accelerator, n—a material that reduces setting time.
accessories, n—products fabricated for the purpose of forming corners, edges, control joints, or decorative effects.
adhesive, n—a substance capable of holding materials together by surface attachment.
admixture, n—a material other than water, aggregates, hydraulic cementitious material, and fiber reinforcement that is used as
an ingredient to modify properties and is added to the batch before or during its mixture.
aggregate, n—an inert granular material which may be added to gypsum plasters. (C35)
all purpose compound, n—a compound formulated and manufactured to serve as both a taping and a finishing compound.
anhydrite, n—the mineral consisting primarily of anhydrous calcium sulfate, CaSO .
arris (of an arch), n—the outside corner or angle formed by the meeting of a wall surface with the curved surface of an arch
(see Fig. 1).
base coat, n—any or all layers of plaster in place prior to application of finish coats.
DISCUSSION—
The first application is normally called a scratch coat and the second application is referred to as a brown coat.
bedding coat, n—that coat of plaster to receive aggregate or other decorative material of any size, impinged or embedded into
its surface, before it sets.
bond plaster, n—a calcined gypsum plaster specially formulated for application over rough monolithic concrete as a bonding
coat for a subsequent gypsum plaster layer. (C28/C28M)
bridging, n—in framing, sections of wood or metal pieces used between framing members to stiffen, give lateral support, and
minimize rotation.
FIG. 1 Arris (of an Arch)
C11 − 23
brown coat, n—the second layer in three-coat plaster application.
building construction joint, n—a designed division of a building that allows movement of all component parts of the building,
in any plane, which may be caused by thermal, seismic, wind loading, or any other force. The construction of the separation is
accomplished by one of the following methods: (1) manufactured devices suitable for this application, or (2) by field fabrication
of suitable materials.
calcined gypsum, n—a dry powder; primarily calcium sulfate hemihydrate, resulting from calcination of gypsum; cementitious
base for production of most gypsum plasters: also called plaster of paris, sometimes called stucco.
calcium sulfate, n—the chemical compound CaSO .
cementitious material, n—a material that, when mixed with water, with or without aggregate, provides the plasticity and the
cohesive and adhesive properties necessary for placement, and the formation of a rigid mass.
check cracking (in joint systems), n—short, narrow cracks randomly oriented in the surface of the dried joint compound.
coat, n—a layer of plaster applied in a single operation.
combined water, n—the water chemically held, as water of crystallization, by the calcium sulfate dihydrate or hemihydrate
crystal.
compressive strength, n—the maximum load sustained by a standard specimen of a material when subjected to a crushing force.
consistency, n—a property of a material determined by the complete flow force relation. (C557)
consistency (normal), n—the number of millilitres of water per 100 g of gypsum plaster or gypsum concrete required to produce
a mortar or a slurry of specified fluidity. (C472)
control (expansion-contraction) joint, n—a designed separation in the system materials that allows for movement caused by
expansion or contraction of the system. The construction of the separation is accomplished by one of the following methods:
(1) manufactured devices suitable for this application, or (2) by field fabrication of suitable materials.
core (of gypsum board), n—the hardened material filling the space between the face and back papers consisting substantially
of rehydrated gypsum with additives.
core (of gypsum panel products), n—the hardened material, consisting substantially of gypsum, with additives, that fills the
space between the face and the back of the gypsum panel product.
cored tile or block,n—see gypsum tile or block. (C52)
cornerbead, n—an accessory for outside corners.
corner reinforcement, exterior, n—a preformed section of wire or expanded sheet steel, for the reinforcement of exterior stucco
external corners (arrises).
C11 − 23
cure (portland cement plaster or stucco), v—(1) to provide conditions conducive to the hydration process of portland cement
plaster or stucco, or (2) to maintain proper temperature and a sufficient quantity of water within the plaster to ensure cement
hydration.
density, n—the weight per unit volume of a material. (C472)
dried sample, n—a sample devoid of free water.
edge (of glass mat gypsum panels), n—the bound edge as manufactured.
edge (of gypsum board), n—the paper-bound edge as manufactured.
edge trim, n—an accessory to cover exposed ends or edges of gypsum board.
embedding compound—see taping compound.
end (of glass mat gypsum panels), n—the end perpendicular to the bound edge. The gypsum core is always exposed.
end (of gypsum board), n—the end perpendicular to the paper-bound edge. The gypsum core is always exposed.
expansion joint,n—see control (expansion-contraction) joint.
face, n—the surface designed to be left exposed to view or to receive decoration or additional finishes.
facer, n—a woven or nonwoven fabric or membrane on the surface of a gypsum board or gypsum panel product that is an
integral part of the product.
featured edge, n—an edge configuration of the paper bound edge of gypsum board that provides special design or performance.
fineness modulus, n—an empirical factor obtained by adding total percentages of a sample of aggregate retained on each of a
specified series of sieves and dividing by 100. The sieve sizes used are: No. 100 (150 μm), No. 50 (300 μm), No. 30 (600 μm),
3 3 1
No. 16 (1.18 mm), No. 8 (2.36 mm), No. 4 (4.75 mm), ⁄8 in. (9.5 mm), ⁄4 in. (19.0 mm), 1 ⁄2 in. (38.1 mm) and larger, increasing
in the ratio of 2 to 1.
finish coat, n—the final layer of plaster applied over a basecoat or other substrate.
finishing compound, n—(sometimes called topping compound) a compound specifically formulated and manufactured for use
over taping or all purpose compounds to provide a smooth and level surface for the application of decoration.
fire-resistance classification, n—a standard rating of fire-resistance and protective characteristics of a building construction or
assembly. (E119)
flame spread classification, n—a standard rating of relative surface burning characteristics of a building material as compared
to a standard material. (E84)
flexural strength, n—the maximum load sustained by a standard specimen of a sheet material when subjected to a bending
force.
C11 − 23
floating, v—the act of spreading, compacting, or consolidating to achieve a specified uniform appearance.
framing member, n—stud, plate, track, joist, furring, and other support to which a gypsum panel product, or metal plaster base
is attached.
free water, n—all water contained by gypsum board or plaster in excess of that chemically held as water of crystallization.
gauging plaster, n—a calcined gypsum plaster designed to be mixed with lime putty. (C28/C28M)
glass mat, n—a woven or non-woven fabric of glass fibers with or without a binder.
glass mat gypsum panel, n—a gypsum panel product with glass mat facers.
grout, n—gypsum or portland cement plaster used to fill crevices or to fill hollow metal frames.
gypsum, n—the mineral consisting primarily of fully hydrated calcium sulfate, CaSO ·2H O or calcium sulfate dihydrate.
4 2
(C22/C22M)
1 5
gypsum backing board, n—a ⁄4 in. to ⁄8 in. gypsum board for use as a backing for gypsum wallboard, acoustical tile, or other
dry cladding.
water resistant gypsum backing board—a gypsum board designed for use on walls primarily as a base for the application of
ceramic, or plastic tile.
gypsum base for veneer plasters, n—a gypsum board used as the base for application of a gypsum veneer plaster.
(C588/C588M)
gypsum board, n—the generic name for a family of sheet products consisting of a noncombustible core primarily of gypsum
with paper surfacing.
gypsum casting plaster, n—a calcined gypsum plaster used primarily to form objects, such as lamp bases, art ware, and
novelties, and so forth. (C59/C59M)
gypsum concrete, n—a calcined gypsum mixed with wood chips or aggregate, or both. (C317/C317M)
gypsum coreboard, n—a ⁄4 in. (19.0 mm) to 1 in. (25.4 mm) gypsum board consisting of a single board or factory laminated
multiple boards, used as a gypsum stud or core in semisolid or solid gypsum board partitions.
gypsum formboard, n—a gypsum panel product used as the permanent form for poured gypsum roof decks. (C318/C318M)
gypsum lath, n—a gypsum board used as the base for application of gypsum plaster. (C37/C37M)
perforated gypsum lath—a gypsum lath having perforations to provide mechanical keying of the basecoat plaster.
foil-backed gypsum lath—the same as plain gypsum lath except that in addition, the back surface shall be covered with a
continuous sheet of pure bright finished aluminum foil.
type X lath—a gypsum lath specially manufactured to provide specific fire-resistant characteristics.
gypsum molding plaster, n—a calcined gypsum plaster used primarily for plaster casts or molds, sometimes used as a gauging
plaster. (C59/C59M, C28/C28M)
C11 − 23
gypsum neat plaster, n—a calcined gypsum mixed at the mill with ingredients to control working quality and setting time.
(C28/C28M)
DISCUSSION—
Neat plaster is either fibered or unfibered. The addition of aggregate is required on the job.
gyps
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