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Plaster Repairs - No Drywall Please!
I have a question: I really enjoyed your
instructions on how to repair drywall. I have to repair plastered walls
and I have already knocked some of the wall out down to the laths. I am on
a budget and I can do this work myself. I don't want to use drywall, I am
going to build the wall up with about 3 layers of material. My question is
what type of material should I use to build the wall up: Joint compound,
Plaster of Paris or pre-mixed spackle?
I am also curious about the term "mud" you used in the
instructions. Is this what you call joint compound? If not could you tell
me what it is?
Thanks for your time; any help you could give would be greatly
appreciated.
Sincerely,
DeeDee
It's
good to hear that you want to avoid using drywall to repair plastered
walls. But there is a good reason that people often replace old plaster
with drywall... plaster is labor-intensive and therefore expensive.
Old fashioned plaster on wood lath used 3 coats. I'm not entirely sure
of the names, and I can't find the info in my reference books, but I
believe the layers are called brown coat, scratch coat, and finish coat.
The brown coat has a lot of sand in it and is applied rather roughly.
The scratch coat was finer, and as it hardened a metal "rake"
tool was dragged through it to scratch it, that is, create tiny ridges
for the final coat to adhere to.
Supposedly you can still buy these three types of plaster today, and the
materials should be available in any larger city that has a lot of older
buildings. Look in the Yellow Pages for plaster suppliers or drywall
suppliers that cater to contractors.
Plastering is probably within the skill level of many people, but it is
HARD WORK. I've never done interior plastering, but I have applied
cement parge coatings to concrete walls, which is essentially the same
procedure, and it always made me sore and tired.
The first house I owned, built in 1950, had plaster over "rock
lath", which is 2' wide drywall panels. I relocated a doorway, and
put a window near the old door opening. I had to fill in a small area of
wall, perhaps 6 square feet, and I didn't want to just use drywall,
because I wanted to keep consistent with the surrounding walls. So I
installed 1/2" drywall and applied a coating of Plaster of Paris. I
had no idea what I was doing. The Plaster of Paris started to harden
before I was done applying it to the wallboard. I managed to make it
work out, though there was a tiny crack at the junction with the old
plaster, because I didn't know I had to use fiberglass mesh tape on all
the seams. I did that job in 1995. I was in my old house recently, and
the owner didn't mention anything about any problems in that spot, but I
also never thought to look at that repair. I know it didn't stand out as
an obvious failure. I guess the moral of the story is: Plaster of Paris
might work in a pinch, but it's not exactly the proper material to use.
Our 1907 project house has plastered walls, and the home's owner wants
to keep plaster in as many rooms as possible. Two years ago we tore out
the plaster from one bedroom and installed Imperial Blueboard, which is
a drywall-like wallboard that is used with "thin-coat" plaster
(also called skim-coat, veneer plaster, and many other names). Thin-coat
plaster is applied in two coats, and it is a very impressive, very
superior wall finish. Thin-coat plaster is far stronger and far harder
than drywall, because the surface is NOT PAPER! We have been really
impressed with thin-coat plaster and advocate it for all homes, new and
old. Here in Northern Michigan it costs about $15 to $18 per square yard
for this finish, in addition to the wallboard. We installed the
wallboard ourselves but hired a plasterer for the finishing. In fact,
we're doing another room next week, and this time we'll be taking some
pictures and writing an article.
Can you do your own thin-coat plaster? Maybe. I wouldn't recommend
starting with the most visible wall in your living room. Maybe a closet
or a bedroom. It must be difficult getting a smooth surface. These guys
have some special tools and a lot of finesse.
There are other options: You can plaster over regular drywall, even
painted drywall, by using a special bonding agent. A company called Larsen
Products (1-800-633-6668) makes a product called Plaster-Weld
that is supposed to let you plaster over drywall. Since this option is
available, your best option might be to just replace your plaster with
drywall and then later pay a plasterer to apply a thin coat using this
bonding agent. Since finishing drywall corners is by far the most
difficult part, you could even just cover the corners with a simple wood
trim, and remove them when it's time to plaster.
As much as I advocate doing things myself, plastering is one thing I
have yet to attempt, because it takes a lot of practice to get good.
Which is why on our 1907 house we are doing everything ourselves except
thin-coat plastering. We want this house to look professionally done.
Regarding your other questions... spackling is a pre-mixed paste
intended to fill very small holes and dents.
Setting-type drywall joint compound (which comes in a powder) might work
for repairing large sections of plaster. You need a mixing paddle and a
powerful electric drill to mix this stuff, or else you will be in for
some serious exercise. This
article shows what I mean.
Pre-mixed drywall joint compound is useless for applying in thick
sections (i.e. more than 1/16") It runs and sags, and takes forever
to harden. Pre-mixed top coat drywall compound (as opposed to General
Purpose compound) is useful for the final coat and is quite hard.
If you want to try using setting-type joint compound for the base coat
for small repairs, and then top coat for the final finish... it might
work, I don't know. Let me know if it does work.
The term "mud" is used throughout the the drywall trades to
mean joint compound, or any gooey material. Mud is also used to describe
thin-set mortar for laying tile, and mortar for laying cement block.
These guys call everything "mud".
Bruce W. Maki, Editor.
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