Tip 1: Fill wide gaps with setting compound—it hardens quickly and won't shrink
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Photo 1: Fill wide gaps with setting-type compound
Mix the setting compound and completely fill all wide gaps. Don't overfill. Keep the fill flush with the drywall surface.
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Photo 2: Setting-type compound when dry
When dry and hard, setting compound completely fills the void, preparing the joint for the tape and next coat.
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Photo 3: Regular compound when dry
Regular compound shrinks as it dries and results in a weak joint that you have to refill. It also takes hours to dry and harden.
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Photo 4: Setting type joint compound bags
Setting-type compound comes in sacks with various hardening rates printed on the bags—20, 45- or 90-min. Buy "lightweight"
setting-type compound,
because it's
sandable in case
you overfill.
Regular drywall
compound shrinks
too much to be
used for wide gaps and
voids (Photos
2 and 3). And it takes days
to dry. Setting compounds, on
the other hand, harden
quickly and hardly shrink
at all. And you can apply
your tape coat as soon as
they harden. No waiting.
You buy setting compounds
powdered in sacks
(photo 4). Mix them
with water in your mud
pan to a paste consistency,
about the same as regular
compound, and press
them into gaps, especially
those wider than about
1/4 in. Keep the fill level
even with, or slightly
below, the surrounding
surface. Work quickly,
because the water activates
a catalyst that causes the
compound to harden. Setting
times vary, depending upon which mix you buy. Start with a 90-
minute setting compound
to give yourself plenty of
working time so it doesn't
harden in your pan (See Tip 4).
Tip 2: Completely fill tapered joints with setting compound
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Photo 1: Properly taped joint
The tape is embedded the in the setting compound, which completely fills the tapered drywall edges, making the wall flat. Regular compound would shrink when dry, creating a dip.
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Photo 2: Spread the compound
First, spread enough setting-type compound to fill the joint pocket.
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Photo 3: Lay on the tape
Lay on the tape and embed it in the compound with a stroke of the taping knife.
Tapered drywall
joints have special
edges that provide
a pocket for joint compound
and tape. They’re
deceptively easy to fill
because there’s plenty of
space for both tape and
“mud.” However, the trick
here is to completely fill the
joint, flush with the surrounding
surface, on your
first coat. If you tape with a
setting compound, it’ll
hardly shrink, so the joint
won’t need further filling (Photo 1).
That eliminates the need
for deft knife work later to
make all the surfaces even.
You can concentrate on
smoothness during the
next two coats.
Scoop up a large lump
of compound and lay it in
quickly, completely filling
the tapers (Photo 2). Lay
on the paper tape and
lightly smooth it into the
mud with your knife
(Photo 3).Finally, spread a
thin coat of mud over the
top of the tape. Make light
strokes with your knife.
Pressing too hard will flex
the blade and depress the
compound, leaving you
with more filling to do with
the next coat.
Tip 3: Bridge from the tape to the wall for smooth inside corners
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Photo 1: Bridge from corner to wall
Create a smooth, crisp joint by resting one end of the taping knife on the tape and the other on the wall. Stroke down to embed the tape.
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Photo 2: Begin with a smooth mud bed
First lay on two
even ribbons of
mud along the
corner. Then
crease the
paper tape in
the middle and
press it into the
mud.
Inside corners are the
easiest joints to tape
smoothly. The key is to
rest one end of your knife
blade on the tape in the corner
and the other on the
drywall surface to create an
even taper along each wall.
Begin by laying a ribbon
of mud about 1/8 in. thick
and 2 in. wide along each
side of the corner (Photo 2). Then sharply
crease the paper tape and
tuck it into the corner. The
crease stiffens the tape and
helps keep the corner
straight and crisp. Quickly
and lightly stroke your
knife over both sides of the
tape to position it exactly
in the corner. Then apply
more pressure and use the
tape on one side and the
wall surface on the other as
leveling guides to embed
the tape smoothly and
evenly. Some mud will
squeeze out, but leaving
about 1/16 in. under the
tape will do. You can leave
an irregular mud edge at
this stage. It’s easy to fill and
smooth during the second
coat.
Tip: Hold your knife at
a slight angle to the adjacent
wall (not square to
it) so you don’t gouge the
mud on it.
Tip 4: Completely fill the corner bead pocket on outside corners
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Photo 1: Corner bead fill
Completely fill corner bead pockets with setting compound. It's stronger than regular compound, and the deep fill won’t shrink.
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Photo 2: OOOPS!
The setting
compound suddenly
hardened! If you don’t
clean your pan completely
after using setting
compound, the leftover
compound will
catalyze the new batch
and it'll harden much
more quickly. You'll be
amazed and amused—
the first time.
Setting compound is
ideal for filling outside
corners or other
places where you use metal
or plastic edge beads. Corner
beads usually leave
about a 1/8-in.mud pocket
(Photo 1), which you want
to completely fill in one
coat. Lay on plenty of mud.
Then simply drag your
6-in. knife along the bead
on one side and the drywall
on the other. Use light pressure;
a heavy hand here will
squeeze out the mud, leaving
a hollow that’ll need
more filling later.
The most common
problems occur when the
corner bead is misaligned,
making the mud pockets
too thin or too thick. To
avoid this problem, always
run your taping knife down
each side of the corner bead
to check the pockets before
you apply compound.
Readjust the corner bead if
necessary.
Tip 5: Apply a thin coat of compound at butt joints
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Photo 1: Taping a butt joint
Since butt joints don’t have tapered edges, apply thin layers of compound below and on top of the tape to avoid a large bump in the wall.
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Photo 2: First, cut away loose paper
Trim away loose drywall paper to prevent lumps and bubbling under the tape.
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Photo 3: Apply compound
Apply a smooth, thin layer of compound over the joint.
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Photo 4: Tape and smooth
Lay on the tape and apply a smooth, thin layer of compound over the tape.
Butt joints, where two
non-tapered edges
meet, are the most
difficult to hide because the
tape sits above the surface of
the drywall. The best advice
is to avoid them like the
plague! Use longer pieces of
drywall if possible (10-ft. or
12-ft.) to span walls and ceilings.
Unfortunately, you
always end up with a few.
The secret of making a butt
joint invisible is to keep your
tape coat as thin as possible.
Begin by cutting a shallow “V”
along the edges (Photo 2).
This removes any fuzzy, torn
or loose paper; trims back
crushed edges; and removes
anything that might protrude
and lift the tape. Slice with a
sharp utility knife here.
Then apply about a 4-in.
wide ribbon of mud about 1/8
in. thick over the joint (Photo
3). Make sure to completely
fill the “V”. Lay on the tape and
embed it with a light stroke of
your knife, leaving no more
than about 1/16 in. of mud
under the tape (Photo 4). Be
sure to apply a thin second
layer of mud over the tape.
Then lightly stroke down each
side to taper the extra mud
away from the center. Once
the compound dries, taper the
edges out a foot or more with
later coats to hide the bump
left by the tape.
One common mistake is to
press too hard and squeeze all
the mud from under the tape.
Then the tape will lift (bubble)
when it dries. You can cut
out occasional bubbles with a
utility knife and remud. But
if whole sections become
loose, you have to scrape off
the old tape and retape.
