Georgia-Pacific ToughRock Gypsum Board - Manual (Page 5)

Finishing
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5
Bead should be installed in one piece. Corner beads,
depending on the type, may be nailed, crimped or
embedded in place with drywall joint compound.
Joints
Finish the joints in four steps. First, apply a coat of
all-purpose joint compound to the joints. Then, imbed
wallboard tape in the all-purpose joint compound,
smooth out bubbles and allow to dry. Next, apply
two successive finish coats over the tape and allow
to dry between coats.
Sand when dry.
Bedding
With your 59 (127 mm)
joint finishing knife, apply
a smooth, full, even coat of
all-purpose joint compound
into the recess created
by the tapered edges of
adjoining boards.
Center a strip of wallboard tape over the joint, and
press it firmly into the wet bedding compound with
your wallboard knife at a 45° angle. Press hard enough
to squeeze a little compound out from the edge of the
tape, but leave enough compound for a good bond.
Let dry about 24 hours.
Taping & Finishing
When the taped bedding coat is dry, apply your first
finish coat of all-purpose joint compound. Extend this
coat a few inches beyond the tape, and feather the
edges. Let dry about 24 hours. Then apply a second
finish coat with your 109 (254 mm) joint finishing
knife. Extend this coat 1
1 ⁄
2 9 (38 mm) wider than the
first finish coat. Wait 24 hours, and sand lightly with
your sanding block and medium grit sandpaper such as
120 or 180 grit. Don’t sand down to the tape. Be very
careful not to sand or scratch the face paper of the
wallboard. Wipe off dust with a damp sponge.
Nail Heads
Draw your 59 (127 mm) joint finishing knife across
the nail head to make sure it is below the surface of
the board. Apply your first coat of all-purpose joint
compound so that it just fills the nail dimple. Don’t
use excess pressure when applying, or your knife may
scoop compound from the dimple. Let the first coat
dry. At least one more coat will be required. A third
coat of all-purpose joint compound may be needed.
Sand lightly after each coat dries.
Butt Joints
Butt joints (square cut edge joints) are finished the
same way as regular joints, with one exception.
Because butt joints are not tapered, you need to be
careful not to allow the joint compound and tape to
build up any more than necessary. To reduce the
effect of the build-up, feather the edges of your finish
coats wider than you would for a regular joint.
Outside Corners
Be sure the cornerbead is attached firmly (see “Corner
Bead’’ in previous section). Use your 59 (127 mm) knife
to spread all-purpose joint compound about 39-49
(76-102 mm) past outside corner. Be sure to cover the
edges. Let dry 24 hours. Apply second coat with your 109
(254 mm) knife. Feather edges 29-39 (51–76 mm) beyond
first coat. Sand lightly when dry.
A third coat may be needed.
Inside Corners
Cut a strip of wallboard tape
the length of the corner you’re
going to finish. Crease the tape
down the center. Use your 59
(127 mm) knife to spread
all-purpose joint compound
about 1
1 ⁄
2 9 (38 mm) on both
sides of the corner. With the
knife press the tape into the corner. Use enough pressure
to squeeze some compound from the edge of the tape,
but leave enough compound to form a good bond.
Feather the compound 29 (51 mm) from the edge of
the tape. Let dry 24 hours, finishing only one side at a
time. Let dry, finish other side of corner. Let dry, then
sand corner. Be careful not to let the compound build
up in the very corner of the tape. Excess compound in
the corner could cause hairline cracks.