To keep solutions concise, let’s divide drywall
for taping seams.
repairs into four groups: nail pops and surface
these tools are great for working
blemishes; fist-size holes through the drywall;
large expanses and creating uni-
larger holes; and discolored, crumbling, or moldy
form, flat surfaces that need little
drywall. Any repair patches should be the same
sanding. “you can put tape and
thickness as the damaged drywall. Drywall-repair
mud up almost as fast as you can
kits with precut patches are available at most
home centers.
run,” notes one pro. most rental
companies supply a video on how
Popped nails and screws are generally a quick
to use these tools, but taking a
fix: Drive another fastener 11⁄2 in. away from the
class in addition isn’t a bad idea.
popped one to secure the drywall. If it’s a popped
Working with paperless Drywall
paperless drywall is a great choice for mold-prone areas such as
basements and bathrooms because, lacking a paper facing, it
denies mold the organic matter it needs to grow. paperless drywall
paperless drywall has a fiberglass mat facing that can produce
hazardous dust. So when working with paperless drywall, use hand
has a fiberglass mat surface instead. Consequently, paperless pan-
tools to minimize dust, and wear a respirator, safety glasses, long-
els must be installed a bit differently.
sleeved apparel, and work gloves.
minimize dust. Airborne fiberglass particles are nasty to
breathe or get on your skin, so wear a respirator that fits tight to
your face, safety glasses, a long-sleeved shirt, and work gloves.
Use hand tools—rather than power tools—to cut panels whenever
possible. Use a utility knife to score and snap panels. When making
cutouts around door and window openings, use a drywall saw rather
than a drywall router.
use adhesive and screws. Because there’s no heavy
paper facing on these panels, it’s easy to drive screws too deep—
which reduces their holding power. So give the screws a little help
by applying a bead of adhesive to stud or ceiling joist edges before
attaching panels with screws. By the way, use 11⁄4-in. drywall
screws to attach 1⁄2-in. or 5⁄8-in. panels—the same as you would
for regular drywall.
use self-adhering fiberglass tape to reinforce panel
joints—rather than paper tape, which mold loves. Use the tape
with a setting-type joint compound, and take it easy with the
taping knife—it’s easy to cut through fiberglass mesh tape.
Finish Surfaces
439
screw, remove it and fill the hole. Cover the old
have metal-and-fiberglass mesh tape.) Use a light
hole and the new screw with at least two coats of touch when applying the first coat of joint com-
joint compound. If it’s a popped nail, don’t try to
pound, pushing the mud through the tape, but
remove it; drive it slightly deeper.
don’t press so hard that you dislodge the mesh.
P R O T I P
When a piece of drywall tape lifts, pull gently
Give the repair three coats of compound,
until you reach a section that’s still well stuck.
feathering out the edges as you go. Take it easy
Drywall seams that coincide
Use a utility knife to cut free the loose tape, cover when sanding. Especially after the first coat, the
with door or window openings
the exposed seams with self-sticking mesh tape,
tape frays easily. By the way, there are precut dry-
are likely to crack vertically.
and apply two or three coats of compound—
wall patches for electrical outlet boxes, which
That’s merely a cosmetic prob-
sanding lightly after each. Because the repair
save time.
lem. But large cracks running
area is small, it doesn’t matter what type of com-
Repairs in which only tape and joint com-
diagonally from the corners of
pound you use, though setting-type compounds
pound cover the hole are OK just for small holes
windows or doors (inside or out)
are preferred.
and gaps.
may be caused by foundation
To repair drywall cracks, cut back the edges of
settling—a problem worth a
Large holes should be cut back until you reach
closer look, perhaps by a struc-
the crack slightly to remove crumbly gypsum and solid drywall. Because mesh tape and compound
tural engineer. For more informa-
provide a good depression for joint compound.
will probably sag if the hole is much wider than
tion, see chapter 10.
Any time the paper face of drywall is damaged,
4 in., holes larger than that should be filled with
cover the damaged area with self-adhering fiber-
a patch of drywall roughly the size of the dam-
glass mesh tape. Then apply three coats of joint
aged area. These patches need to be backed with
compound.
something solid so they’ll stay put.
Small holes in drywall are often caused by door-
The easiest backing is a couple of furring
knobs, furniture, or removed electrical outlet
strips cut about 8 in. longer than the width of the
boxes. Clean up the edge of the hole so the sur-
hole and placed on both sides of the hole. To
face is flat. Then cover the hole with self-adhering install each furring strip, slide it into the hole,
fiberglass mesh tape. (Better drywall-repair kits
and while holding it in place with one hand,
Texturing Drywall and plaster
joint compound is a marvelous medium for texturing a drywall
For an open-pore, orange-peel look, use a stiff-bristle brush or
patch or matching the texture of existing plaster. All that’s needed is a
whisk broom to jab compound that is just starting to dry. jab lightly
little ingenuity.
and keep the bristles clean.
For a stippled plaster look, place joint compound in a paint tray,
To achieve the flat but hand-tooled look of real plaster, apply
thin it with water until it is the consistency of thick whipping cream,
the compound in short, intersecting arcs. Then knock down the high
and roll it onto the wall or ceiling using a stippled roller. Don’t over-
spots with a rubber-edged Magic Trowel®, as shown below.
roll the compound, or you’ll flatten the stipples.
if you’re trying to duplicate a slightly grainy but highly finished
Create an irregular “splatter” texture by thinning the compound
plaster surface, trowel on the topping coat as smoothly as possible and
to a heavy-cream consistency, sucking it into a turkey baster, and
allow it to dry. Then mist the surface slightly and rub it gently with a
squirting it onto the wall.
rubber-edged grout float.
you can achieve the irregular, hand-tooled look of plaster by covering
Before the compound starts to set, us
e a rubber-faced Magic Trowel to
drywall with joint compound applied in tight, intersecting arcs. Because
knock down high spots and partially smooth out the knife marks. The
of its crack resistance, use 90-minute or 120-minute setting-type
trowel should glide. Unload excess compound into your mud tray after
compound. It’s OK if the drywall isn’t completely covered.
each pass, and sponge the rubber edge clean every four or five passes.
440 Chapter 15
screw through the drywall into the wood. Screws pLASTeRIng
will pull the furring strips tight to the back of the
drywall. Then cut the drywall patch, place it in
the cutout area, and screw it to the strapping.
Cover the edges of the drywall patch with self-
adhering mesh tape, fill the screw holes, and
apply joint compound—three coats in all. Here, a
setting-type compound, such as Durabond® 90, is
a good bet because it dries quickly and is unlikely
to sag. The more skillfully you feather the com-
pound, the less visible the patch will be.
For holes larger than 8 in., cut back to the
centers of the nearest studs. Although you should
have no problem screwing a replacement piece
to the studs, be sure to back the top and the bot-
tom of the new piece with lengths of 1x4 furring.
The best way to install backing is to screw fur-
ring strips to the back of the existing drywall.
Then position the replacement piece in the hole
1. If casing, baseboards, or floors are already
and screw it to the gussets, using drywall screws,
installed, cover them with paper and tape to
protect them from plaster splatters.
of course.
Discolored, crumbling, or moldy drywall is
caused by exterior leaks or excessive interior
moisture. Be sure to attend to those causes before
repairing the drywall. Excessive moisture is often
the result of inadequate ventilation, which is
especially common in kitchens and baths. Leaks
2. Mix the plaster to the consistency of soft-
around windows and doors are often caused by
serve ice cream before ladling it onto a
inadequate flashing over openings.
mason’s hawk. For skim-coat plaster, follow
If the drywall is discolored but solid and if
the manufacturer’s mixing instructions,
which typically recommend adding 12 qt. to
you’ve remedied the moisture source, wash the
15 qt. of water for each 50-lb. bag of plaster.
area with soap and water, allow it to dry thor-
oughly, and prime it with white pigmented
shellac or some other stain-resistant primer.
The same solution works for minor mold on
sound drywall.
However, if there’s widespread mold and the
drywall’s crumbling, there’s probably extensive
mold growing inside the walls. You’ll need to rip
out the drywall—and possibly some of the fram-
ing—and correct the moisture problems before
replacing the framing and finish surfaces. In
basements where condensation is common in
summer months, however, you’ll be well advised
to install paperless drywall when it comes time to
replace finish surfaces.
Chapter 14 covers mold abatement at greater
length.
Plastering
This section is limited to plaster repairs because
applying plaster takes years to master. The tools
3. To prevent cracking, cover blueboard seams
4. . . . . sweep the trowel in an upward arc to
needed for plaster repair are much the same as
with self-adhering mesh tape. Load your trowel
spread the plaster, then back down to embed
those needed for drywall repair: a screw gun or
from the hawk and . . .
it (make it adhere). As you apply plaster, the
cordless drill; 6-in. and 12-in. taping knives; a
blade shouldn’t lift off the surface. Sweep the
mason’s hawk; and a respirator if you’ll be
blade back and forth, covering bald spots and
removing or cutting into plaster. There’s a lot of
erasing trowel marks. Use a double-bladed
knife on the corners.
Finish Surfaces
441
grit, so wear goggles, too. The tools and tech-
Brown
niques for plaster are similar to those needed for
coat
stucco, which is discussed in chapter 7.
zzzzzz Keying plaster to Wood Brown
Scratch
ANATOMy OF A plASTER jOB
coatcoat
Traditional plastering has several steps:
Scratch
Finish
1.
coat
Nail the lath to the framing.
coat
2. Trowel a scratch coat of plaster onto the
Finish
Lath
lath. The wet plaster of this coat oozes through
coat
the gaps in the lath and becomes a mechanical
Lath
key when it hardens.
Stud
3. Trowel on, then roughen the brown coat
after it has set slightly.
Stud
4. Trowel on a finish, or white coat, which
becomes the final, smooth surface.
In the old days, plasterers often mixed animal
hair into scratch and brown coats to help them
stick. As a result, old plaster that’s being torn out
is nasty stuff to breathe. The finish coat was usu-
ally a mixture of gauging plaster and lime for
uniformity. Scratch coats and brown coats were
This plaster cross section shows how the
left rough and were often scratched with a plas-
scratch coat of plaster oozes through the lath
terer’s comb before they set completely so the
and hardens to form keys, the mechanical
This plaster cross section shows how the
next coat would have grooves to adhere to. Finish
connection of plaster to wood.
scratch coat of plaster oozes through the lath
coats were quite thin (1⁄16 in.) and very hard.
and hardens to form keys, the mechanical
Lath can be a clue to a house’s age. The earliest about the same time, plasterers b
connection of plaster to wood. egan using
wood lath was split from a single board so that
small paper-coated panels of gypsum instead of
when the board was pulled apart (side to side), it
wood or metal lath. Called gypsum lath or rock
expanded like an accordion. Although metal lath
lath, the panels were so easy to install that they
was available by the late 1800s (it was patented
dominated the market by the 1930s. But time and
in England a century earlier), split-wood lath
techniques march on. After World War II, drywall
persisted because it could be fashioned on site
all but replaced plaster as a residential surface.
with little more than a hatchet. By 1900, however,
most plasterers had switched from lime plaster to
SMAll REpAiRS
gypsum plaster, which dried much faster. And
Small cracks or
holes in plaster can be filled with
patching plaster or a setting-type joint compound
such as Durabond 90, which sets in 90 minutes.
Repair or Replace plaster?
Because joint compound is softer, sands easily,
and sets slower than patching plaster, it’s easier
To decide whether plaster should be repaired or replaced, first assess how well it is
to work with. Setting-type joint compounds are
attached to the lath. To do this, near stains, cracks, holes, or sagging sections, press
better for patching than drying-type joint com-
the plaster with your hand. if the plaster is springy, it has probably separated from
pounds, which just aren’t as strong. To ensure a
its lath and must be reattached before you try to repair it.
good bond, strip paint from the surfaces you’re
if the plaster has a few surface cracks and isolated holes but is stable, it can
patching and sand the adjacent areas lightly
be repaired.
before applying compound.
if there’s widespread discoloration and cracks wider than 1⁄4 in., but the plas-
Small cracks in plaster are repaired by stripping
ter’s basically stable, cover it with 1⁄4-in. or 3⁄8-in. drywall or replace it.
surface paint, cleaning loose plaster, and under-
if you see water stains, crumbling plaster, and widespread cracking or sagging
cutting the cracks slightly with a knife or a small,
surfaces, remove the plaster and replace it with drywall. if there are water stains, of
sharp-pointed lever-type can opener (also called a
course, find and repair the leak before doing any other work. Widespread sagging
“church key”). Undercutting allows the patching
suggests that lath has pulled away from framing. Although lath can be reattached,
material to harden and form a key that won’t fall
concomitant plaster damage will usually be so extensive that you’re better off tear-
out. Before patching, wet the exposed plaster
ing out the plaster.
well and brush on a polyvinyl acetate (PVA)
442 Chapter 15
bonder such as Plaster-Weld® or Elmer’s White
type W drywall screws and plaster washers,
Glue to bond the patch to the old plaster.
which fit under the heads of the screws. A screw
Over the crack, stretch a length of self-adhering gun is good for this operation.
fiberglass mesh. Then use a taping knife to spread
However, before you attach the screws, mark
the joint compound or patching plaster over the
their locations on the plaster, and use a spade bit
Renovation 4th Edition Page 103