3.2.3
Control And Expansion Joints
See Section 09205N FURRING AND LATHING for [wall] [and] [ceiling] joint
installation requirements. [Install control joints at locations indicated
before applying gypsum plaster. Vertical joints must be continuous and butt
horizontal joints against the vertical joints.] Check expansion, control
joints and accessories to ensure unrestrained movement, metal lath not
continuous behind the joints, and
area between joints do not exceed 14 sq m 150 sq ft.
3.2.4
Curing
3.2.4.1
Gypsum Plaster
Before the plaster has set, provide environmental controls to prevent the
plaster from drying too fast. After the plaster has set, provide for rapid
drying to develop high strength.
3.3
GYPSUM PLASTER WORK
ASTM C 842.
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NOTE: Gypsum basecoat plaster may be by one of two
methods for a three-coat or two-coat (double back)
systems. The three-coat plaster system will require
a basecoat of a scratch coat, cross raked, partial
drying, and a brown coat. The two-coat plaster
system requires a scratch coat and a brown coat that
is applied (double back) within a few minutes to the
unset (moist) scratch coat. The cross raking of the
scratch coat is omitted in the double back system.
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3.3.1
Gypsum Plaster Thickness Requirements
Plaster thicknesses are from face of metal lath plaster base (scratch coat)
or solid base surfaces.
a.
Vertical Surfaces
Base Types
Base Coat
Finish Coat
Total Thickness
Metal Lath
13 mm
3 mm
16 mm
Masonry
13 mm
3 mm
16 mm
Concrete
13 mm
3 mm
16 mm
Other Bases
10 mm
3 mm
13 mm
Base Types
Base Coat
Finish Coat
Total Thickness
Metal Lath
1/2
in
1/8
in
5/8
in
Masonry
1/2
in
1/8
in
5/8
in
Concrete
1/2
in
1/8
in
5/8
in
Other Bases
3/8
in
1/8
in
1/2
in
b.
Horizontal Surfaces.
Total plaster thickness for metal lath
SECTION 09210
Page 14
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