My friend has an 80 year old house with mostly plaster walls. In some
places, old paint and surface plaster has fallen off, leaving uneven patches
(maybe 1/16 of an inch deep and 1 square foot in size).
The problem is that, when using the pre-mixed light compounds, during
sanding some of his patches detach themselves from the substrate, even
though he has rough-sanded the surfaces before spackling.
Are there spackling coumpounds that have better adherence than others?
Don't know of compounds with more grip. Perhaps adding some glue might
Rather than that, I would make each hole as deep as the plaster and
then patch away. Also, sanding before applying spackling leaves a
smooth surface with which the compound doesn't have a good bond.
The pre-mixed compound is not the best because it hardens through
evaporation. Some of that moisture will go back into the underlying
plaster and give a poor bond. If the dust from the rough sanding
wasn't thouroughly removed with a vaccuum that can also to contribute
to the problem. Mixing plaster of paris or a setting compound, such as
Durabond, is not as hard as it seems and will work much better than the
pre-mixed. Just follow the directions and safety precautions. This is
one time you really want to wear a dustmask, gloves and goggles. It's
more work, but you'll have a longer lasting patch.
Find a broken window-screen and replace it. Cut a portion of the old
window screen out. Coat the area you are patching with a light coat of
mud and then press the window screen into the wet mud. Use short
(3/4") drywall screws to firmly attach the taught window screen to the
wall. Don't skim on the screws; use a lot. Go back over the screen
with another layer of mud.
Hope this helps,
Probably the finish coat of plaster leaving the brown coat visible.
Don't use the "light" pre-mix; it's the weakest there is. The only
advantage is ease of sanding -- oh, yeah, it's lighter to carry home
too <g>. Better is to use the regular pre-mix.
Another poster suggested using plaster. Bad idea for the last 1/16".
Impossible to level and sand. Even plasterers use drywall compound for
the final skim coat.
The wire screen idea sounded interesting but an awful lot of work. If
it were me I'd scratch the brown coat (a dog grooming rake works well
but you could probably use an old screwdriver), then apply Plaster
Weld (in the paint section), then fiberglass mesh tape or patch, and
finally regular drywall compound.
Plaster Weld is really good stuff even when used contrary to the label
on powdery plaster. Slosh it on. Two coats even.
Adhesion to what? It's not the adhesion of the compound that's the
problem; it's the solidity of the surface you're applying it to.
Use regular joint compound IMHO. I usually moisten the bare spot with water
to keep the moisture from the new compound being sucked into the
sub-surface, and allowing the new compound to dry a bit slower. Never had a
patch come unstuck. YMMV.
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