tape. Sand the first coat of joint compound light-
to countersink a hole 1⁄8 in. deep for each washer.
ly, leaving it a little rough so the second coat
Sunk below the surface of the plaster, the screw
adheres better. Then apply the second coat, feath-
heads and washers will be easy to cover with
ering it out to blend in the patch’s edges.
patching compound.
When the patch dries, sand it lightly with fine,
Place screws and washers every 8 in. to 10 in.
220-grit sandpaper, wipe it clean, allow it to dry
on both sides of the crack and anywhere else the
thoroughly, and prime the patch with an oil-
plaster seems springy and disconnected from the
based primer.
lath. Once you’ve stabilized the crack in this man-
ner, scrape, tape, and fill it, as described earlier.
Large cracks often accompany sections of
bowed or sagging plaster, which have pulled
Small holes, the size of an electrical outlet, are
free from the lath. If the plaster is sound—not
easy to fill if the lath is still in place. Remove any
crumbling—you can reattach it to the lath using
zzzzzz patching Cracked plaster
zzzzzz patching Holes in plaster
Plaster
Lath
Original
wood lath
missing
Plaster
1/8-in.
washer
recess
Spade bit
Metal lath
Wire loop
replacement
Pencil
holding lath
in place
If plaster lath has been cut out, replace it
before patching the hole. Insert and secure
a smal section of wire lath with a wire looped
around a pencil, as shown. Twirl the pencil
Cracked plaster often means that it has
to draw the wire lath tight to the back of
pulled free from its lath. Use screws and
the plaster, then fill the hole with two coats
plaster washers to reattach it, countersinking
of patching plaster. Unwind the wire and
them so they’ll be easier to patch.
snip it when the first coat is hard.
Finish Surfaces
443
loose plaster, brush out the debris, wet the lath
and the surrounding plaster well, brush on a PVA
bonder, and trowel in patching material. Leave
zzzzzz Casting larger
Replacement Molding
the first coat a little rough, let it dry well, and
apply bonder again before troweling in a second,
RTV-rubber-and-
Replacement
smooth coat.
cheesecloth mold
casting
If the hole has no lath behind it, you’ll need to
add some. Scrape the loose plaster from the edge
of the hole. As shown in “Patching Holes in
Plaster” on p. 443, cut a piece of metal lath larger
than the hole and loop a short piece of wire
through the middle of the lath. Then, holding the
ends of the wire, slide the lath into the hole. To
pull the lath tight against the back of the hole,
insert a pencil into the front of the loop and turn
the pencil like an airplane propeller until the wire
is taut. The pencil spanning the hole holds the
lath in place.
Sand bed to
After wetting the lath and surrounding plaster,
support mold
Box
spread a rough coat of compound into the hole.
When the coat has set, unwind the wire, remove
When a repetitive plaster pattern is
the pencil, and push the wire into the wall cavity.
damaged, replace damaged sections with
The hardened plaster will hold the metal lath in
castings made from sections that are intact.
place. Trowel on the finish coat.
Large holes with lath intact should be partially
patched with a piece of drywall slightly smaller
the lath—textured side out. The patching plaster
than the hole. Because a hole with square cor-
will ooze through the holes in the pegboard and
ners is easier to patch than an irregular one,
harden in the same manner that plaster keys into
square up the edges of plaster using an oscillat-
the spaces between lath strips.
ing multitool or an oscillating multitool with an
abrasive wheel. (Wear safety glasses.) Be careful
RESTORiNg plASTERWORK
not to cut through the lath. Use type W drywall
Restoring damaged crown molding, medallions,
screws to attach the drywall to the lath behind,
or other plaster ceiling ornaments takes patience,
stretch self-adhering fiberglass mesh tape around hard work, and a lot of skill. You may be better
the perimeter of the patch, and apply joint com-
served replacing the originals with plastic or
pound or patching plaster as described earlier.
composite reproductions. They are good looking,
For best results, the drywall should be slightly
lightweight, easy to install, and—once painted—
thinner than the existing plaster so you have
indistinguishable from plaster ornaments. Given
some room to build up and feather out the patch.
the hourly rates of a skilled plasterer, this strategy
As an alternative, pegboard is a dandy sub-
is usually far more cost-effective.
strate for these patches because you can cut it
However, if your plaster ornament has a repet-
easily with a jigsaw to fit irregular holes. Hold a
itive pattern with only a few damaged sections,
sheet of 1⁄4-in. pegboard over the plaster, eyeball
you can cast replacement sections by creating a
and trace the shape of the patch through the
mold from an original, undamaged section.
holes in the pegboard, and screw the pegboard to Removing an ornamental section. If you want
to make a casting, you need to remove an undam-
aged ornamental section. First, support the sec-
JUST
tion that you will remove. To do this, position a
Wiggle yOUR FinGeRS 2x4 tee, its head covered with rubberized floor
to mix plaster, pour it into water as you wiggle your fingers in the bottom of the pan.
padding, under the ornament to cushion and
mixed that way, the plaster will set slowly and will be usable longer. if you pour water
protect any delicate details. Then use a circular
into plaster, on the other hand, it will start setting within 5 minutes.
saw with a Carborundum blade or a recipro-
plaster is easier to clean up if you mix it in a plastic tub. allow it to dry, then strike
cating saw with an 18-teeth-per-inch (tpi), bimetal
or twist the bottom of the tub to make the plaster fall out in chunks.
demolition blade to cut around the section. The
section should include a complete pattern repeat
plus 2 in. on each end to allow for some damage
444 Chapter 15
when you remove the piece. This is dusty work
Before cutting the new casting to length, min-
and you’re sure to hit nails, so w
ear a respirator
imize fragmentation by first scoring the cutting
mask and goggles.
line with a utility knife and then cutting with a
Note: There may well be wires or pipes run-
fine-toothed hacksaw.
ning through the ceiling, so explore beforehand
How you attach the replacement piece
after turning off the electricity to the area. In
depends on its composition. If your casting is
many cases, ceiling joists will be exposed in the
plaster, use Durabond 90 quick-setting com-
attic above. Plan cuts so they miss wires and
pound to adhere the plaster ornament to the lath.
pipes. Replacing the section will be easier if you
Dampen the replacement piece so it doesn’t leach
don’t cut through the lath, but that’s sometimes
moisture from the Durabond, and use the 2x4 tee
impossible to avoid. After cutting around the sec-
to support it until the compound sets—about
tion, you can often slide a chisel behind it and try 90 minutes. For good measure, predrill holes at a
to break off the plaster keyed into lath spaces.
slight angle every 10 in. along the edge of the cast-
ing to receive drywall screws with plaster wash-
Casting replacement sections. To reproduce
ers. If your replacement casting is a lightweight
replacement sections, you must first create a
polymer, you won’t need screws; a few beads of
mold. Room temperature vulcanization (RTV)
construction adhesive or white glue will do the
silicon rubber, made by combining two compo-
job. Before setting the replacement piece, dry-fit
nents, is a good choice for molds: It can duplicate it to make sure it’s the same thickness as the old
fine details and is available from most arts-and-
plaster; you may need to build it up slightly. Last,
crafts stores and online. After you’ve removed an
fill the cracks or flaws where the new sections
original section in good condition, use a tooth-
join old before painting the restored ornaments.
brush to remove flaking paint, then repair any
small damage with plaster of paris. Shellac the
section so its surface will be slick, and let it dry.
Soundproofing
To make the mold, paint on a coat of RTV sili-
Soundproofing is serious science. Done correctly,
cone rubber, and allow it to dry. Thereafter, alter-
it’s much more complicated and expensive than
nate strips of cheesecloth and rubber, allowing
just adding fiberglass batts between studs or ceil-
each RTV-and-cloth layer to dry before applying
ing joists. Fortunately, there are commonsense
the next coat. Three or four layers should give you solutions that won’t cost all that much and will
a mold that’s sturdy enough. When the final coat
go a long way toward mitigating sound. But first,
is dry, peel the RTV mold off the original plaster
a little science about how sound travels.
section, and pour a new casting into the mold.
Basically, sound travels through the air or
Although plaster is a suitable casting material, through the structure of a building. Airborne
it’s heavy. If the original object is large—for
sounds travel in radiating waves through open-
example, a ceiling medallion—consider casting
ings of any size. Those sound waves continue
with a lightweight polymer such as polyurethane
until their energy is absorbed—and the more soft
or polystyrene, which won’t shrink, paints well,
or porous materials they encounter, the sooner
and is available in different densities. Or you may that energy is spent. Structure-borne sounds are
need to support the mold in a bed of sand so the
transmitted through contact between solid mate-
new casting material doesn’t distort the mold.
rials, and those solids can be as small as a copper
For larger casts, fill a large enough box with
supply pipe in contact with a wall plate or a dry-
sand, and—before peeling the mold from the
wall screw sunk in a ceiling joist. To stop struc-
original plaster section—press the mold into the
tural sounds, you need to isolate them, say, by
sand. Then lift out the mold, and peel the rubber
putting a piece of foam or heavy vinyl between a
carefully from the original plaster. Return the
vibrating appliance and the floor it sits on.
empty mold into the impression it made in the
Point being, because noise—the sounds we
sand. Pour the new plaster (or polymer), and
don’t want to hear—can travel through tiny open-
level it off to the top of the mold. When the cast-
ings or be transmitted through structural ele-
ing is completely dry, lift it and the mold out of
ments as small as a screw, successful soundproof-
the box, and peel off the mold.
ing is all about paying attention to details. How
installing new castings. Once you have cast
many details you can attend to will depend on
replacement sections, measure both the damaged the extent of your renovation. If you’re gutting
and replacement sections carefully so the repeti-
the interior, you can do a lot. But even a room
tive pattern will match exactly when you install
left intact can be improved.
them. Then cut out the damaged ceiling sections,
leaving the lath intact and being careful to cut
the ends as cleanly and squarely as possible.
Finish Surfaces
445
THREE SiMplE SOlUTiONS
glass insulation. ABS or PVC waste pipes are
inherently noisy, however, so if you want to
It’s finally happened: You’re somebody’s parent
silence flushing noises in waste pipes forever, bite
and you’re telling your kid to TURN IT DOWN!
the bullet and install cast-iron DWV pipes. Less
So next birthday or holiday, get that sonic-busting expensive is making sure that DWV pipes are
offspring or your hard-of-hearing mother a pair
well secured with pipe straps, hangers, and
of really nice headphones, ones so nice and cushy clamps (see the top right photo on p. 333) and
that he or she will want to wear them. You will be supply pipes are immobilized by Acousto-Plumb
spared exploding aliens or the evening news at
clamps (see the top photo on p. 345) and other
60 decibels (db.), and peace will reign. Second,
plastic pipe-support flanges.
if footfalls in a room overhead have you edgy, a
Electrical cables and devices are pretty quiet
carpet with a substantial pad can be a better
as mechanical systems go, but their routing holes
sound suppressor than installing insulation
and cutouts for outlet boxes will transmit air-
between floor joists. Third, heavy curtains, over-
borne sounds—especially when outlet boxes are
stuffed furniture, and rugs will all absorb sound,
back to back in a shared wall. Fill holes in fram-
whereas hard, reflective surfaces such as tile or
<
br /> ing with expanding foam, caulk around outlet
laminate counters can make living spaces sound
boxes, and, if you want to do an A1 job of stop-
as homey as a hospital corridor.
ping air leaks and hence sounds, wrap outlet
Appliance science. Any appliance with a motor
boxes in dense vinyl jackets. However, do not
will vibrate and create noise. Washers, dryers,
wrap recessed ceiling cans. IC-rated light fixtures
and refrigerators are the biggest offenders
(see pp. 393–394) can be covered with loose
because they have the biggest motors. Your appli- insulation or insulation batts (but not vinyl
ances aren’t noisy? Put your ear to the floor when jackets). However, non-IC-rated fixtures must
they’re running. To mitigate appliance noises in
not be covered with insulation—or anything else
P R O T I P
an upstairs in-law unit, master carpenter Alan
that would cause these fixtures to overheat and
Jencks of Berkeley, Calif., installed the type of
cause a house fire.
When using resilient channel
thin foam pad typically used under floating
for soundproofing, use screws of
floors, covered that with 1⁄4-in. plywood under-
SOUNDpROOFiNg BETWEEN FlOORS
two different lengths. The longer
screw, typically 11⁄4 in., will
layment, and then installed resilient flooring atop Correctly soundproofing between floors may
attach the channel to the fram-
that in the apartment’s kitchen and laundry
require gutting finished ceilings and exposing
ing. The shorter screw, say, 1 in.,
room. But Jencks wasn’t done. He mounted the
joists. The soundproofed ceiling on the facing
will attach the drywall to the
washer and dryer on a plywood platform fas-
page shows one approach, which requires access
channel— but not to the framing.
tened to the steel-and-neoprene vibration isola-
from above and below to create a “sandwich”
in other words, if the screws
tors often used to mount commercial cooling
of doubled 5⁄8-in. drywall panels filled with
attaching the drywall reach the
units to roofs. Granted, his solution took a few
R-19 fiberglass batts. Two noteworthy details:
framing, they will transmit sound
Google searches, but it solved the problem with-
The doubled drywall on the ceiling is not screwed
through the structure.
out tearing up the floorboards.
to joists but to resilient channels, which allow
Renovation 4th Edition Page 104