Specification

Directions Preparation Protect the product from moisture during storage and on the job. In cold weather, heat the interior of the building to a
minimum of 55 °F (13 °C) for an adequate period before the application of plaster, while basecoat and finish is being applied,
and until the finish is dry. Air circulation should be kept at a minimum level during this period.
Warning: Store all I MPERIAL
Brand Gypsum Base flat. Panels are heavy and can fall over, causing serious injury or death. Do not move unless authorized.
Under normal working conditions, joints of veneer plaster systems may be treated by applying I
MPERIAL Brand Type P
(pressure-sensitive) or Type S (staple) to the joints and then applying the veneer plaster basecoat or finish to preset the tape.
However, there are a number of special situations that require the use of a setting-type joint treatment system.
— High building temperature, low humidity or excessive evaporation that creates “rapid drying” conditions.
— Metal framing is specified.
— Certain wood-framing applications with spacing of 249 o.c. (see Maximum Spacing table above).
Under any of these conditions, use S
HEETROCK Brand Joint tape and S HEETROCK Brand Setting-Type (D URABOND ) or Light-
weight Setting-Type (E
ASY S AND ) Joint Compound to treat all joints and internal angles. Allow the joint treatment to set and
dry thoroughly before plaster application.
Installation I MPERIAL Brand Gypsum Base may be installed either perpendicular (preferred) or parallel to the framing. All ends and edges
should be placed over framing members except where edge joints are perpendicular to framing. Use maximum practical
lengths to minimize end joints. Install gypsum base first on ceilings and then on walls. Over steel studs, arrange direction of
installation so that the lead edge of the base is attached to the open side of the stud flange first. Bring base panels into
contact with each other, but do not force into place. Fit abutting ends and edges neatly; stagger end joints; arrange joints on
opposite sides of partition so they occur on different studs.
Begin driving fasteners in center of panel and work toward ends and edges, holding gypsum base in firm contact with
framing. Space fasteners as shown in table and not less than 3/89 from edges and ends of panel. Drive fastener heads flush
with surface without breaking the face paper. If gypsum base appears to be loose from framing, install additional fasteners.
Float vertical and horizontal interior corners by placing fasteners 89 out from the corner. Where framing is parallel with the
corner, attach one panel to corner framing and float the abutting panel. Cut and fit gypsum base neatly around pipes and
other openings. Remove loose face paper around cuts and use quick-setting plaster to close openings.
Control Joints—Apply control joints, where required, over the face of the gypsum base. Cut to required lengths with fine-
toothed hack saw. Cut end joints square, align and butt together slightly gapped. Attach the control joint to gypsum base
temporarily with 9/169 rosin-coated staples spaced 129 o.c. along each flange. Complete the installation of the control joint
with fasteners (nails or screws) driven through the control joint flange into the framing on each side of the joint. The protec-
tive plastic tape over the open groove should be left in place until finishing is completed.
Metal Trim—Fasten gypsum base in normal manner but omit fasteners at framing member where metal trim is to be
installed. Leave a space 3/89 to 1/29 wide between edge of base and face of jamb or wall. This provides space for hardware
or door bucks and allows for expansion when trim is used for perimeter isolation. Slip trim over edge of base with expanded
mesh flange on face side. Fasten to base by nailing or stapling 129 o.c.
Vinyl Trim—Slip vinyl trim over gypsum base with long flange behind base. Install the base with the trim firmly abutting the
surface.
Corner Bead—Apply to all external angles. Hold tightly against angle and fasten to base by nailing or stapling 129 o.c. alter-
nately on both flanges along entire length.
Acoustical Sealant—Seal edges of gypsum base around entire perimeter of partition. Also, seal air-tight all penetrations of
the gypsum base, particularly electrical boxes. In addition to sealing the perimeter of electrical boxes, coat the back sides
with a layer of acoustical sealant. Apply acoustical sealant under control joints and similar openings between the gypsum
base and abutting materials.