USG Manufactured Housing Handbook User Manual

Page 21

removed from the working area,
along with any other material or
tools that may have been left on
the floor. It is easy to trip over
something while you are concen-
trating on the wall or ceiling you
are finishing.

3 Mixing

Mix the chosen joint compound in
accordance with the manufac-
turer’s instructions. Be sure to
use the amounts of water and
compound indicated on the joint
compound package.

Tips
Always give ready-mixed com-
pound a quick initial mix before
adding water; compound varies in
its initial thickness.

For fill coats on corner bead, add
only a small amount of water.

For taping or finish coats with
mechanical tools, the compound
should be very thin. Add almost a
quart of water per bucket.

Always add your water gradually,
in half-pint increments, until the
desired thickness is reached.

Check viscosity by lifting the mixer
from the compound and watching
the mixture drip from the tool. For
a final viscosity determination,
pass a knife blade through the mix
and observe how the compound
flows back together.

When mixing powder com-
pounds, sift powder into the water
while agitating with the mixer. A
thick initial mix will provide shear
to break down lumps. After a
short soak time, adjust the mix to
the desired consistency.

4 Prefill

Prefill all gaps over 1/8

Љ wide.

Prefilling makes for stronger
joints and a better finished sur-
face. The time spent on prefilling
will be made up during later
stages, because wiping down will
be easier, and finish coats will dry
more quickly.

5 Taping (Automatic Taping

Tool Method)
Make sure that the prefill material
has set. Check the consistency of
your compound to ensure that it
will pump easily into the auto-
matic taping tool. Thin with water
if needed. Pump compound into
the automatic taping tool from the
pail using a hand pump and
gooseneck attachment.

Apply joint tape and compound to
the butt joints first. Wipe down
with a flexible 8

Љ knife, removing

excess compound.

Apply tape to the tapered joints
next.

Last, apply tape to the inside cor-
ners. The creaser wheel on the
automatic taping tool folds tape
into the corner.

When the inside corners have
been taped, use the corner roller
to press the tape into the corner.
Then, pass a 2

Љ-3Љ corner fin-

isher (attached to its pole handle)
over the corner, leaving a uniform
coat of compound over the tape
(except at the ends).

Remove any excess compound
using a hand knife.

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ning of the row. Draw the spotter
smoothly along the entire row, apply-
ing moderate pressure to force the
compound onto the wallboard sur-
face. The blades of the nail spotter
will skim off excess compound, leav-
ing a slight crown directly over each
dimple.

After passing over the last dimple,
gradually break contact with the sur-
face using a sweeping motion. This
will result in properly filled dimples
without leaving excess compound to
be removed by hand.

Hand Pump

A hand-operated pump is used to
transfer compound into mechanical
tools from the pail. It comes with dif-
ferent attachments to fit the various
types of tools that may be used. You
may also wish to fill your pan using
the pump when doing handwork.

A screen in the intake opening of the
pump filters particles in the com-
pound. Use a coarse screen with tap-
ing compound, and a fine screen
with finish compound. If pumping
becomes difficult, scrape off the par-
ticles that have accumulated on the
screen.

Drill with Figure 8 Drywall Mixing Bit

For mixing compound, a 7 amp, 450
max. rpm drill with a figure-8-type
drywall mixer bit is effective. The
heavier amp drill does not wear out
as quickly as lesser amp drills, and
the figure 8 paddle mixes quickly and
thoroughly. Faster drills may whip
more air into the mix, resulting in
craters in the compound when it is
applied.

Hand Stomper

This tool provides an alternative to
electric drills for mixing. The hand
stomper, which looks like an over-

sized potato masher, is especially
handy for making slight adjustments
to the thickness of a mix. It is also
useful for scraping down compound
from the sides of the bucket, and for
moving compound to the bottom of
the bucket so that air is not sucked
into the intake of the pump. A long-
handled stomper may also be used
to move compound from the bucket
into a banjo or pan.

Procedures for Joint Finishing
Using Mechanical Tools

1 Choosing Materials

When choosing joint tape and
compound for use in mechanical
drywall tools, always consult the
tool manufacturer’s recommen-
dations. If you decide to use a set-
ting-type joint compound, bear in
mind that this type of compound
sets fairly quickly, and will cause
clogging if allowed to harden
inside of your tools. Prompt and
frequent cleaning is required
when setting-type compounds
are used with mechanical taping
tools.

2 Drywall Inspection and

Preparation
Inspect and prepare surface as
described in the section on hand
finishing. That is: set fasteners
below surface of panels; ensure
that panels are tightly attached to
framing; cut away any soft spots
or bulges; remove torn or loose
face paper; cut butt joints in a “V”
groove. Brush away all dust and
other foreign materials.

Tip
Mechanical tools operate more
smoothly when you move quickly.
Be sure to eliminate any potential
obstacles that may slow your
progress or create dangerous sit-
uations. Drywall scrap should be

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