Eliminate as many hard-to-hide butt joints as you can
To hide “butt joints” (where two non-tapered
ends of drywall meet), you
have to build up a hump of joint compound
that's very thin and wide. This
is time consuming and difficult to do
well. So if you're a novice drywall finisher,
avoiding butt joints is smart.
The best way to avoid butt joints is
to use sheets of drywall that are long
enough to cover entire walls and ceilings.
As a result, you'll have only
tapered joints to finish. Drywall
sheets are commonly available in
8- and 12-ft. lengths, and specialty
suppliers carry 14-ft. sheets (in the
yellow pages under “Drywall”).
If your ceiling is longer than 14 ft.,
you can't avoid butt joints. But you
can avoid butt joints on a wall that
exceeds 14 ft. Simply hang the sheets
vertically rather than horizontally.
That way, you'll have several tapered
joints to cover, but no butt joints.
Hanging drywall vertically is slower
than hanging it horizontally because
you have to make sure the tapered
edges fall at the centers of studs. Cut
the first sheet to width so the tapered edge lands on the center of a
stud. After that, the edges of each
sheet should fall perfectly on studs. If
you run into misplaced studs, nail
2x2s to them. If you have 9-ft. ceilings,
call a drywall supplier to find
Use mesh tape, not paper
Pros use paper tape to strengthen
joints. But in less-skilled hands,
paper tape can ripple, slip out of
place or trap air bubbles. If you push
too hard as you embed paper tape,
you'll squeeze out all the joint compound
behind it and the tape will
peel off later. Adhesive-backed mesh
tape eliminates all those glitches. Just
stick it in place and it stays put, leaving
you free to concentrate on
spreading a smooth coat of mud.
And since it doesn't require an
underlying layer of compound, mesh
allows for a thinner buildup over butt
joints and repairs. You can use mesh
anywhere except inside corners.
But mesh tape has one weakness
(literally): It's not as strong as paper.
To compensate, you have to cover it with setting-type joint compound,
which is stronger than premixed compound
(see tip below). Apply mesh
tape no more than a few hours before
you're ready to cover it. Left uncovered,
it will eventually fall off.
Fill joints faster with setting-type compound
Mixing up setting compound is a messy nuisance,
but it's worth it. Setting compound has three key
advantages over premixed versions: It allows you to
use mesh tape, it hardens fast and it
shrinks much less. Quick hardening and low shrinkage
make setting compound perfect for deep filling.
A thick layer of premixed compound takes days to
dry and shrinks. You'll need several coats to fill the
depression, and the more layers you add, the harder
it is to get smooth results.
For small repair jobs, you can mix setting compound
with a paint paddle. For larger jobs, use a
corded drill with a 12-in. long mixer attachment. Don't buy a 24-in. mixer unless you
have a powerful 1/2-in. drill. The key to a smooth,
chunk-free mix is to let it stand for about five minutes
after the initial mixing.
That lets the chunks
absorb water before
final mixing. Setting
compounds have different
hardening times, ranging
from 5 to 210 minutes. The
45- or 90-minute versions are
best for most jobs. Be sure to
choose a “lightweight” setting
compound. Other versions become so hard that sanding away mistakes is nearly impossible. Even the lightweight versions are harder to sand than premixed
compound, so it's best to use setting compound for the
first coat and premixed compound for later coats. Be sure to
clean tools before the setting compound hardens.
Coat inside corners faster and smoother with a corner knife
It takes a steady hand to embed tape in
inside corners with a standard drywall
knife. One little slip of the knife
and you'll gouge one side while
you're smoothing the other. An
inside corner knife not only
eliminates that problem but does the
job faster. Outside corner knives are
also available, but we don't recommend
them, since corner bead makes smoothing outside
corners almost foolproof.
Apply compound and place the tape as usual. Then
load some mud onto the corner knife to lubricate the
knife and leave a thin coat of compound over the paper.
Start at the top of the corner and drag the knife down to
about 16 in. from the floor. Then start at the floor and
drag upward. Ease off when you reach the area that's
already smooth. You may have to repeat this process two
or three times to fully embed the tape and create a
smooth, straight corner. A corner knife doesn't ensure
straight corners, so reinforced corner tape is a good idea. Use a corner knife for the first coat only; after
that, coat one side at a time, allowing one side to harden
before you coat the other.
Dunk paper tape to avoid bubbles and bulges
Paper tape can ripple, slip, bulge and bubble. But you can
minimize these problems by dropping it into a bucket of
water. Wet paper tape is more pliable than dry tape, so it
traps fewer air bubbles behind it. Water also makes the
paper slick, so your knife slides over the tape without creating
ripples or creases. Wetting doesn't eliminate the
squeeze-out problem, so you still have to be careful to leave
a thin layer of mud between the tape and the drywall. Don't
let the tape soak—that will soften the paper and make it
more susceptible to scuffs and tears.
Keep corners straight with reinforced tape
Inside corners are tough to keep neat and straight. Unless
you have a very steady hand, your knife can wander as you
embed the tape. And if you create a wavy corner with the
first coat of mud, creating a straight corner with subsequent
coats is almost impossible.
The solution is to use tape that's backed with metal or
plastic strips (available in100 ft. rolls at home centers). This tape is
especially helpful on odd-angled corners, which are very
hard to keep straight. It's still possible to create
a wavy corner if you push too hard, so
apply light, even pressure as you smooth
the joint compound. The strips reduce
ripples and bubbles too, so there's no
need to wet the tape. Don't overlap the
tape where inside corners meet the ceiling.
Instead, cut the tape short to avoid a
triple-thick buildup of tape.
Flatten bumps and bulges between coats for less sanding later
Everyone hates the dust cloud raised
by sanding drywall. And the best
way to minimize sanding later is to
knock down high spots between
coats. Left alone, these high spots
will grow higher and wider (and
harder to fix) with each coat. Don't
worry about low spots; subsequent
coats will fill them.
If you used setting-type compound,
inspect the joints before the
compound has hardened completely.
Run a 12-in.-wide knife over every
joint. The blade will scrape off small
ridges and nubs. More important, it
will act as a straightedge, revealing
larger bumps and bulges. When the
compound is about the consistency
of a bar of soap, you can easily shave
down bulges without gouging. You
can sand and scrape setting compound
after it's completely hard, but
that's more work.
With standard joint compound,
however, it's best to let each coat dry
completely before inspecting, scraping
and sanding. The surface of partially
dry standard compound may be
firm while the underlying material
remains soft and easy to gouge.
Create a smooth surface with a knockdown knife
Feathering out a butt joint or skim-coating a whole wall
is difficult because your knife leaves ridges on the broad
surface—and touching them up often creates even more
ridges. The solution is a “knockdown” knife. With its soft
rubber blade, this squeegee-like tool floats over the surface,
flattening ridges without creating new ones.
A knockdown knife won't scrape down big bulges or
fill wide depressions, so make the surface as flat as you
can with a 12- or 14-in. metal knife first. Then drag the
knockdown knife gently over the surface in one continuous
pass. Apply light, even pressure and don't stop or hesitate.
On a butt joint, you'll have to make two or three
passes to smooth the whole surface. You can make more
passes if necessary, but stop before the compound starts
to harden. Although the rubber blade is soft, it can still
make a mess of partially hardened compound.
Knockdown knives are available in 18- and
22-in. widths at drywall suppliers and some home centers
and hardware stores. A 22-in. version is best for butt
joints. To order one online, search for “knockdown knife.”
For smooth walls faster, finish with topping compound
Any type of joint compound can hold tiny air or water
bubbles that leave pockmarks on the surface. But you'll get
fewer pockmarks with “topping” compound. Topping
compound looks just like other versions of premixed joint
compound, but it has a creamier texture. That smooth consistency
makes it easier to feather out and creates a glossy
surface with very few pockmarks. It also shrinks less as it
dries. With all these advantages, topping compound helps
you get to the final sanding stage with fewer coats and fewer
fixes between coats. And when the time comes, you'll find
that topping compound is the easiest compound to sand.
Topping compound has poor bonding strength, so don't
use it for the first coat.
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Keep crumbs out of your mud to prevent scars
You can't create a smooth surface using joint compound
that has crumbs of hardened compound in it. One tiny
chunk clinging to your knife will leave a scar across the
whole joint. Cleanliness is the key to keeping your mud free
of chunks. Scrape down the insides of the bucket every
time you scoop out mud. Then wipe the sides clean with a
wet rag. At the end of the day, cover the compound with a
thin layer of water. The water will remain on top of the
compound, so you can pour it off before you use the
Never dump leftover
compound from your
mud pan back into the
bucket; just throw it
away. To keep the
pan and tools clean
between uses, scour
them with an abrasive
sponge or immerse
them in water. Setting-type
continue to harden
even under water, so
wash tools as soon as
you're done. Never
send large amounts
of setting compound
down the drain—it
can plug pipes.