Building Design and Construction Handbook - Merritt - Ventech!

WALL, FLOOR, AND CEILING SYSTEMS 11.67
wallboards, two parallel beads should be applied near each edge of the framing.
Along other supports a single, continuous, straight bead is adequate. Adhesive,
however, should not be applied to members, such as diagonal bracing, blocking,
and plates, not required for wallboard support.
The number and spacing of supplemental fasteners needed with adhesives depend
on adhesive properties. Stud adhesives generally require only perimeter fasteners
for walls. One fastener should be driven wherever each edge or end crosses
a stud. For edges or ends bearing on studs, fasteners should be spaced 16 in c to
c. The same perimeter fastening should be used for ceilings, but in addition, fasteners
should be spaced 24 in c to c along all framing crossed by the wallboard.
Where perimeter fasteners cannot be used, for example, with predecorated wallboard
for which joint treatment is unnecessary or undesirable, prebowing or temporary
bracing should be used to keep the wallboard pressed against the framing
until the adhesive develops full strength. Bracing should be left in place for at least
24 hr. Prebowing bends in wallboard so that the finish side faces the center of
curvature. The arc is employed to keep the board in tight contact with the adhesive
as the board is pressed into place starting at one end.
11.26.3 Multi-Ply Gypsumboard Construction
A multi-ply system consists of two or more layers of gypsumboard attached to
framing, furring, masonry, or concrete. This type of system has better fire resistance
and sound control than can be achieved with single-ply systems, principally because
of greater thickness, but also because better insulation can be used for the base
layer.
Face layers usually are laminated (glued), but may be nailed or screwed, to a
base layer of wallboard, backing board, or sound-deadening board. Backing board,
however, often is used for economy. When adhesives are used for attaching the
face ply, some fasteners generally are also used to ensure bond.
Maximum support spacing depends principally on the thickness of the base ply
and its orientation relative to the framing, as indicated in Table 11.11, and is the
same for wood or metal framing or furring.
Nails, screws, or staples may be used to attach base ply to supports. For wood
framing, when the face ply is to be laminated to the base ply, staples should be
spaced 7 in c to c (Fig. 11.24), and nails and screws should be single-nailed as
recommended for single-ply construction (Art. 11.26.2). If the face ply is to be
nailed, nails and staples for the base ply should be driven 16 in c to c, and screws
24 in c to c. For metal framing and furring, Type S screws for the base ply should
be spaced 12 in c to c if the face ply is to laminated, and 16 in c to c if the face
ply is to be attached with screws.
For attachment of the face ply with adhesive, sheet, strip, or spot lamination
may be used. In sheet lamination, the entire back of the face ply is covered with
adhesive, usually applied with a notched spreader. In strip lamination, adhesive is
applied by a special spreader in grouped parallel beads, with groups spaced 16 to
24 in c to c. In spot lamination, adhesive is brushed or daubed on the back of the
face ply at close intervals. Partitions with strip or spot lamination provide better
sound control than those with sheet lamination.
Supplemental fasteners or temporary bracing is required to ensure complete bond
between face and base plies. If a fire rating is not required, temporary fasteners
may be placed at 24-in intervals. For fire-rated assemblies, permanent fasteners
generally are required, and spacing depends on that used in the assembly tested