Plaster
Board
Question
Some of the plaster has come off my walls, revealing some sort of
plasterboard underneath. Can I put up new plaster on that under layer
material?
Answer
That plasterboard stuff is Rocklath, a good lath that took the place
of wood lath in 1930's, 1940's, and the 1950's. You can put up new plaster,
or you can buy gypsum plaster and put on a rough coat, then scratch
that rough coat before it sets completely. After the gypsum plaster
dries completely, finish with a smooth plaster coat. You'll need a steel
trowel to put the new plaster in place. If the Rocklath is soft or yields
to the poke of a finger, it has gotten excessively wet, and will not
hold the plaster and has to be replaced. Measure the thickness of the
old plaster, and substitute a piece of plasterboard of an appropriate
thickness. Use an adhesive caulk or construction adhesive to do the
gluing.
*****
Question
I patched a wall with plasterboard, about 29 by 15 inches. The patch
fits well enough, but the top is slightly off. It sticks out beyond
the plane of the wall but just a little bit. How can I fix that?
Answer
Check the stud behind the patch; there might be a wayward nail that
is keeping the patch from correctly settling on the stud. Or, the patch
might be warped a little and nailing along the edge should flatten it
out, If not try a new patch, If that fails, check the stud to make sure
it is not warped. If it is, plane it down a bit. When putting drywall
patch, make sure you have a least two nailing surfaces, opposite each
other, to secure the patch properly. And leave a 1/4- inch gap around
the patch so you can fill it with joint compound, smooth it out and
apply paper tape, and finish off the tape with three super-thin layers
of joint compound. If you do not use the paper tape, the joint will
crack within weeks.
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