ASTM C 11 :- Standard Terminology Relating to Gypsum and Related Building Materials and Systems1

  This standard covers terminology relating to gypsum
and related building materials and systems. The terms are
generically defined.

3. Terminology

• Accelerator—a material that reduces setting time.
• Accessories—products fabricated for the purpose of forming
  corners, edges, control joints, or decorative effects. 
• Adhesive—a substance capable of holding materials together
  by surface attachment. 
• Admixture—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—an inert granular material which may be added
  to gypsum plasters. (C35) 
• All purpose compound—a compound formulated and
  manufactured to serve as both a taping and a finishing
  compound.
• Anhydrite—the mineral consisting primarily of anhydrous
  calcium sulfate, CaSO4. 
• 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
• Anhydrite, n—the mineral consisting primarily of anhydrous
  calcium sulfate, CaSO4.
• 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.
• Bridging, n—in framing, sections of wood or metal pieces used
  between framing members to stiffen, give lateral support,
  and minimize rotation. 
• 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 CaSO4. 
• 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.
• 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.
• 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 (arises).
  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
  FIG. 1 Arris (of an Arch) 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), No. 16 (1.18 mm), No. 8 (2.36 mm), No. 4 (4.75
  mm), 3⁄8 in. (9.5 mm), 3⁄4 in. (19.0 mm), 11⁄2 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 fireresistance and protective characteristics of a building construction or assembly. 
•  flame spread classification, n—a standard rating of relative
  surface burning characteristics of a building material as
  compared to a standard material.
•  flexural strength, n—the maximum load sustained by a
  standard specimen of a sheet material when subjected to a
  bending force.
  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. (
•  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, CaSO4·2H2O or calcium sulfate dihydrate.
• gypsum backing board, n—a 1⁄4 in. to 5⁄8 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. 
• (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. 
• Gypsum concrete, n—a calcined gypsum mixed with wood
  chips or aggregate, or both. 
• Gypsum core board, n—a 3⁄4 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. 
• 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. 
• 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. 
• Gypsum panel products, n—the general name for a family of
  sheet products consisting essentially of gypsum.
• Gypsum plaster, n—the generic name for a family of powdered
  cementitious products consisting primarily of calcined gypsum with additives to modify physical characteristics, and
  having the ability, when mixed with water, to produce a
  plastic mortar or slurry which can be formed to the desired shape by various methods and will subsequently set to a
  hard, rigid mass. 
• gypsum sheathing, n—a gypsum board used as a backing for
  exterior surface materials, manufactured with waterrepellant paper and may be manufactured with a waterresistant core. 
• gypsum tile or block, n—a cast gypsum building unit. (C52)
  gypsum veneer plaster systems, n—veneer plaster applied in
  accordance with Specification C843 to gypsum base for
  veneer plasters. 
• Gypsum wallboard, n—a gypsum board used primarily as an
  interior surfacing for building structures. 
• foil-backed gypsum wallboard—a gypsum wallboard with
  the back surface covered with a continuous sheet of pure bright
  finished aluminum foil. 
•  type X gypsum wallboard—a gypsum wallboard specially
  manufactured to provide specific fire-resistant characteristics
  (C36/C36M). 
• Gypsum wood-fibered plaster, n—a calcined gypsum plaster
  containing shredded or ground wood fiber added during
  manufacture. 
• Hemihydrate, n—the dry powder, calcium sulfate
  hemihydrate, resulting from calcination of CaSO4·2H2O,
  calcium sulfate dihydrate. 
• See calcined gypsum.
  joining, n—the juncture of two separate plaster applications of
  the same coat, usually within a single surface plane.
• joint compound, n—generic term referring to all compounds
  used for taping or finishing gypsum board, or both. See all
  purpose compound, finishing compound, taping compound. 
• joint tape, n—a strip of tape made from paper, metal, fabric,
  glass mesh, or other material, that is commonly used in a
  joint system to reinforce the joints between adjacent gypsum
  panel products. 
• glass-mesh joint tape, n—joint tape made from multidirectional glass yarn. 
• Paper joint tape, n—joint tape made from paper and designed to be embedded in the joint compound. 
• Self-adhering joint tape, n—a glass-mesh joint tape designed
  to adhere without requiring mechanical attachment. 
• Keene’s cement, n—an anhydrous gypsum plaster characterized by a low mixing water requirement and special setting
  properties, primarily used with lime to produce hard, dense
  finish coats. 
• key, n—the grip or mechanical bond of one coat of plaster to
  another coat, or to a substrate.
  DISCUSSION—It may be accomplished physically by the penetration of
  wet mortar or crystals into paper fibers, perforations, scoring
  irregularities, or by the embedment of the lath.
  lath—see gypsum lath.
• load-bearing partition, n—a partition designed to support a
  portion of the building structure. 
• Machine direction, n—the direction parallel to the paperbound edge of the gypsum board. 
• Manufactured sand, n—the fine material resulting from the
  crushing and classification by screening, or otherwise, of
  rock, gravel, or blast furnace slag.
• masonry cement, n—a hydraulic cement for use in mortars for
  masonry construction, containing one or more of the following materials: portland cement, portland blast furnace slag
  cement, portland-pozzolan cement, natural cement, slag
  cement, or hydraulic lime; and in addition usually containing
  one or more materials such as hydrated lime, limestone,
  chalk, calcareous shell, talc, slag, or clay as prepared for this
  purpose. 
• Mechanical bonds, n—the attachment created when plaster
  penetrates, into or through, the substrate, or envelops irregularities in the surface of the substrate. 
• Members (in application of gypsum panel products),
  n—framing to which gypsum panel products are attached. 
• Mill-mixed plaster (ready-mixed plaster), n—material formulated and dry-blended by the manufacturer, requiring only
  the addition of and mixing with water. 
• Mortar, n—a mixture of gypsum plaster with aggregate or
  hydrate lime, or both, and water to produce a trowelable
  fluidity. 
• Natural sand, n—the fine granular material resulting from the
  natural disintegration of rock or from the crushing of friable
  sandstone. (C35)
  neat gypsum plaster—see gypsum neat plaster. 
• Nominal thickness (of gypsum panel products), n—the
  manufacturer-stated thickness of the gypsum panel product.
  perlite aggregate, n—a siliceous volcanic glass expanded by
  heat.
• perm, n—a unit of measurement of water vapor permeance; a
  metric perm, or 1 g/24 h·m2
  ·mm Hg. U.S. unit, 1 grain/
  h·ft2
  ·in. Hg. 
• (E96/E96M) permeability, n—the property of a porous material that permits
  a fluid (or gas) to pass through it; in construction, commonly
  refers to water vapor permeability of a sheet material or
  assembly and is defined as water vapor permeance per unit
  thickness. Metric unit of measurement, metric perms per
  centimetre of thickness. See water vapor transmission,
  perm, permeance.
• permeance (water vapor), n—the ratio of the rate of water
  vapor transmission (WVT) through a material or assembly
  between its two parallel surfaces to the vapor pressure
  differential between the surfaces. Metric unit of measurement is the metric perm, 1 g/24 h·m2
  ·mm Hg; U.S. unit, 1
  grain/h·ft2
  ·in. Hg. See water vapor transmission,
  permeability, perm.
• Plaster bond, n—the adhesion between plaster coats or between plaster and substrate. 
• Plastic cement, n—a hydraulic cement to which one or more
  plasticizing agents (but not more than 12 % by volume) have
  been added during intergrinding or blending to increase the
  workability and molding qualities of the resultant cement
  paste, mortar, or plaster. 
• Plasticity, n—the property of freshly mixed cement paste,
  mortar, or plaster which determines its workability and
  molding qualities. 
• Portland cement, n—a hydraulic cement produced by pulverizing clinker consisting essentially of hydraulic calcium
  silicates, and usually containing one or more forms of
  calcium sulfate as an interground addition. 
• portland cement plaster, n—a plaster mix in which portland
  cement or combinations of portland and masonry cements or
  portland cement and lime are the principal cementitious
  materials mixed with aggregate. 
• Purity, n—the percentage of CaSO4·
  1⁄2 H2O in the calcined
  gypsum portion of a gypsum plaster or gypsum concrete, as
  defined by Specification C28/C28M, for Gypsum Plasters.
  The percentage of CaSO4·2H2O in the gypsum or the
  gypsum portion of fully hydrated, dry, set gypsum plaster. 
• Ready-mixed plaster, n—a calcined gypsum plaster with
  aggregate added during manufacture. (C28/C28M)
  recessed edge, n—see tapered edge 
• Relative humidity, n—the ratio of actual water vapor pressure
  to the saturation water vapor pressure at the same
  temperature, expressed as a percentage. 
• Retarder, n—a material that extends setting time.
  round edge, n—a rounded, paper-bound edge formation on
  gypsum board, commonly used for gypsum lath.
• Saddle-tie, for furring, n—a single or double strand of wire
  used to attach furring members to framing members of wall
  or ceiling assemblies. See Fig. 2.
  saddle-tie, for furring, v—to attach furring members to framing members of wall or ceiling assemblies using a single or
  double strand of wire. See Fig. 2.
  saddle-tie, for wire hangers, v—to attach wire hangers to main
  runners. See Fig. 3.
  sample as received, n—a representative portion of product or
  material in the state received by the testing laboratory. 
• Scratch coat, n—the first layer of plaster applied over lath or
  other substrate.
  set, n—the chemical and physical change in plaster as it goes
  from a plastic, workable state to a rigid state. See setting
  time. 
• Setting time, n—the elapsed time required for a gypsum plaster
  to attain a specified hardness and strength after mixing with
  water. 
• Shipment (of gypsum panel products), n—the quantity of
  gypsum panel products shipped by a manufacturer and
  included on a single invoice. 
• Smooth-trowel finish, n—a uniform finish free of grainy or
  coarse areas, trowel marks, or other avoidable imperfections. 
• Spinout,, n—the continued rotation of a screw without further
  penetration into the substrate. 
• Steel drill screw, n—self-drilling screw with the ability to drill
  its own hole and form or cut mating threads without
  deforming its threads or breaking.
• Stucco, n—a portland cement-aggregate plaster mix designed
  for use on exterior surfaces. See portland cement plaster. 
• Synthetic gypsum, n—a chemical product, consisting primarily of calcium sulfate dihydrate (CaSO4·2H2O) resulting
  primarily from an industrial process. 
• Tapered edge, n—an edge formation of gypsum board which
  provides a shallow depression at the paper-bound edge to
  receive joint reinforcement. Also known as a recessed edge. 
• Taping compound, n—(sometimes called embedding compound) a compound specifically formulated and manufactured for use in embedding of joint reinforcing tape at
  gypsum board joints.
  temper, v—to mix or restore to a workable consistency. 
• Texture finish, n—any applied decorative finish other than
  smooth.
  three-coat work, n—plaster applied in three successive coats
  with time between coats for setting or drying, or both.
  topping compound—see finishing compound. 
• Veneer plaster, n—a calcined gypsum plaster formulated to be
  applied in thin coats. (C587)
  vermiculite aggregate, n—a micaceous mineral that expands
  with heat. (C35)
  wallboard—see gypsum wallboard. 
• water absorption, n—the amount of water absorbed by a
  material under specified test conditions commonly expressed
  as weight percent of the test specimen. 
• water-repellent paper, n—gypsum board paper surfacing
  which has been formulated or treated to resist water penetration. 
• water-resistant core, n—a gypsum board specially formulated
  to resist water penetration.
  water vapor transmission (WVT), n—the rate of water vapor
  flow, under steady specified conditions, through a unit area
  of a material, between its two parallel surfaces and normal to
  the surfaces. Metric unit of measurement is 1 g/24 h·m2
  . See
  permeability,permeance, perm. 
• Wood-fibered plaster, n—a calcined gypsum plaster containing shredded or ground wood fiber added during manufacture.