Plaster and Gypsumboard Construction Terms

Bed, or Bedding, Coat. The first coat of joint compound over tape, bead, or fastener heads.
Bed Mold or Bed. A flat area in a cornice in which ornamentation is placed.
Bench, Hangers. A low scaffold used by workers to reach the ceiling.
Binder. A chemical added during formulation of the gypsumboard core, often starch, to improve bond between the core and paper facings.
Bleeding. A discoloration, usually at a joint, on a finished wall or ceiling of gypsumboard.
Blister. Protuberance on the finish coat of plaster caused by application over too damp a base coat, or troweling too soon, or a loose, raised spot on the face of a gypsumboard, usually due to an airspace or void in the core. Also denotes a bulge under joint reinforcing tape, usually caused by insufficient compound under the tape.
Blow. Separation of a large area of paper facing from the core during the manufacturing process and usually appearing as a large, puffy blister or a full loose sheet of paper.
Board Knife. A hand tool that holds a replaceable blade for scoring or trimming gypsumboards
Board Saw. A short handsaw with very coarse teeth used to cut gypsumboards for framed openings for windows and doors.
Bond Plaster. A plaster formulated to serve as a first coat applied to monolithic concrete.
Boss. A Gothic ornament set at the intersection of moldings.
Broad Knife. A wide, flexible finishing knife for applying joint-finishing compound.
Brown Coat. Coat of plaster directly beneath the finish coat. In two-coat work, brown coat refers to the base-coat plaster applied over the lath. In three-coat work, the brown coat refers to the second coat applied over a scratch coat.
Bubble. A large void in the core of gypsumboard caused by entrapment of air while the core is in a fluid state during manufacture.
Buckles. Raised or ruptured spots in plaster that eventually crack, exposing the lath. Most common cause for buckling is application of plaster over dry, broken, or incorrectly applied wood lath.
Bull Nose. This term describes an external angle that is rounded to eliminate a sharp corner and is used largely at window returns and door frames.
Butterflies. Color imperfections on a lime-putty finish wall, caused by lime lumps not put through a screen, or insufficient mixing of the gaging.

Caging. Framing, usually of metal, used to enclose pipes, columns, beams, or
other components to be concealed by gypsumboard.
Capital or Cap. The ornamental head of a column or pilaster.
Case Mold. Plaster shell used to hold various parts of a plaster mold in correct position. Also used with gelatin and wax molds to prevent distortions during pouring operation.
Casing Bead. A bead set at the perimeter of a plaster membrane or around openings to provide a stop or separation from adjacent materials.
Casts. (See Staff.)
Catface. Flaw in the finish coat of plaster comparable to a pock mark.
Coffered. Ornamental ceilings composed of recessed panels between ribs.
Contact. Ceilings attached in direct contact with the construction above, without use of runner channels or furring.
Cross Furred. Ceilings applied to furring members attached at right angles to the underside of main runners or other structural supports.
Furred. Ceilings applied to furring members attached directly to the structural members of the building.
Suspended. Ceilings applied to furring members suspended below the structural members of the building.
Chamfer. A beveled corner or edge.
Chase. A groove in a masonry wall to provide for pipes, ducts, or conduits.
Check Cracks. Cracks in plaster caused by shrinkage, but the plaster remains bonded to its base.
Chip Cracks. Similar to check cracks, except the bond is partly destroyed. Also referred to as fire cracks, map cracks, crazing, fire checks, and hair cracks.
Circle Cutter. An adjustable scribe for cutting circular openings in gypsumboard for lighting fixtures and other devices.
Cockle. A crease-like wrinkle or small depression in gypsumboard paper facing, usually extending in the long direction.
All-Purpose. A joint treatment material that can be used for bedding tape, finishing, laminating adhesive, and texturing.
Joint. A cementitious material for covering joints, corners, and fasteners in finishing of gypsumboard installations, to produce a smooth surface.
Setting-Type. A joint compound that hardens by chemical reactions before drying and that is used for shortening the time required for patching and completing joint finishing.
Taping. A joint compound specially formulated for embedment of joint tape.
Topping. A joint compound specially formulated to serve as the final finishing coat for a joint, but not intended for embedment of tape.

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