How to Repair Plaster Walls and Ceilings
Repairing Plaster
In modern construction gypsum
wallboard is used to provide the finish on interior
walls and ceilings. Gypsum wallboard (commonly
called sheetrock) came into existence during the
1950s. Thanks for gypsum wallboard!
Prior to the 1950s plaster was very commonly used
for finishing interior walls and ceilings. Plaster
is very hard and durable but because it isn’t
resilient it has a tendency to crack as a home
settles or slightly moves from earthquakes. Once a
crack is formed larger pieces of plaster may
eventually work loose.
How to Repair Plaster Walls and Ceilings:
A simple mixture of Portland cement, fine sand, and
water makes a good plaster repair and can be
applied over wood lath, metal mesh, special gypsum
wallboard (blue board), or a masonry surface. To
perform the repair a scratch coat is applied onto
the backing material, then a thick undercoat is
toweled onto the surface, and then a finish coat is
applied.
Most home supply centers sell a plaster repair
cement that will work well for making these
repairs.
For small cracks and holes usually can be repaired
with regular drywall spackling compound. Simply
widen the small cracks to about 1/8 of an inch and
clean the opening of any dust and debris. Fill the
crack with the spackling compound and then sand the
compound in a circular motion after it is dried
using fine grade sandpaper. Prime the patch with a
sealer before painting.
For larger cracks undercut the crack to help bond
the new plaster to the old plaster. Clean out the
dust and debris. Dampen the crack with water and a
sponge then fill the crack over half the depth of
the crack with patching plaster. Score the plaster
when firm (not hard) to provide a rough surface for
the next layer. Dampen the dry patch again and
apply the next layer to within 1/8 of an inch of
the surface. Let the patch thoroughly dry before
applying the finish coat. Fill with finishing
plaster and remove any excess.
For a smooth finish to the texture use a metal
float or taping knife dipped in water and smooth
out the surface. When dry, sand to remove minor
imperfections, prime, and paint.
For a more textured surface, use a paintbrush,
sponge, or wire brush to achieve the desired
finished texture. Swirl the plaster in a uniform
overlapping pattern. To create peaks in the plaster
use a brush with bristles. When the surface starts
to stiffen, draw a clean taping knife over the
surface to smooth out the peaks. Let the plaster
dry and prime and paint.
Steps for repairing plaster:
1.
Prepare the hole by removing any cracked plaster
from the edges of the hole with a cold chisel and
hammer. Undercut the edges to ensure a good bond.
Clean any dust or debris and then dampen the edges
with a sponge.
2.
Apply the first coat of plaster material by filling
a little more than half the holes depth with
patching plaster. Force it through any gaps in the
lath underneath. Score the plaster when firm and
let it dry so the second coat will adhere to the
surface.
3.
Apply a second coat by dampening the patch again
and apply the second layer of plaster to within 1/8
inch of the surface. After it dries score the
plaster to provide rough surface for the next
layer.
4.
Apply the finish coat using a taping knife to apply
finishing plaster. Feather the edges an inch or
more beyond the edges of the patch. Remove any
excess wet plaster. For a smooth finish to the
existing texture use a metal float or taping knife
dipped in water and smooth out the surface. When
dry sand to remove minor imperfections, prime, and
paint.
That is all there is to it. Repairing plaster walls
and ceiling cracks and holes is different than
repairing gypsum drywall. It takes a little
practice and patients buy most home owners can
perform the repair themselves.
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