I need to do some repairs to my 53 year-old plaster walls. The lath is
metal mesh grid, which holds a sandy colored base. And the finish coat
(yes, there might be another layer between this and the base) is a
nice, smooth, creamy colored surface. I have a lot of patience and am
willing to do it the way professionals would if I have to.

I have some narrow cracks that I can dig out to hold the plaster patch.
Exactly what type of plaster is used here? Gauging plaster with lime?
Moulding plaster? The guy at my office who repaired the plaster walls
(and did a fantastic job) said he used lime and moulding plaster.

For larger areas, where pieces have broken away all the way down to the
lath, do I need to use two types of plaster?...One for the base to bond
with the lath and rest of the base and one for the finish surface?

And for cracks that might open up again, should I dig down a little and
bury fiberglass tape across the joint and below the surface?

Mike

For cracks, spackling compound will do as long as the base coat is sound
(no movement).

For small areas you could try finishing plaster, but do a couple of
layers or three. Your final coating should be quite thin, easily less
than an eighth of an inch. That is the only one that has to be level.

For larger areas, you need a base coat plaster (perlited gypsum) for the
base coat, leaving about a quarter inch for finishing coats (two is
best) with finishing plaster. Around here, perlited gypsum comes in 80
pound bags, which is a lot of plaster. But if you do have large areas
that need this, do the small areas in the same manner. Allow each coat
to dry thoroughly before putting on the next. I water each coat with a
sprinkler bottle before putting on the next coat.

Plastering is a real art (which is why so many now only do drywall), but
if your original walls are very smooth, you can usually match that with
careful work and probably some sanding. If the surface you are matching
is dimpled or patterned, matching it is quite a challenge, but I had
good results once patting it down with a damp sponge.

I don't know what moulding plaster is, but if it is plaster of paris, I
would not use it. Likewise, I've never seen a real plasterer use tape,
except possibly in corners if the lath doesn't meet, and even then, it
is just used to keep the base coat from falling through the gap, not
really as a strengthening measure. Tape is used with drywall, which is
not nearly as strong as a real plaster wall.

wrote:

I need to do some repairs to my 53 year-old plaster walls. The lath is
metal mesh grid, which holds a sandy colored base. And the finish coat
(yes, there might be another layer between this and the base) is a
nice, smooth, creamy colored surface. I have a lot of patience and am
willing to do it the way professionals would if I have to.

I have some narrow cracks that I can dig out to hold the plaster patch.
Exactly what type of plaster is used here? Gauging plaster with lime?
Moulding plaster? The guy at my office who repaired the plaster walls
(and did a fantastic job) said he used lime and moulding plaster.

For larger areas, where pieces have broken away all the way down to the
lath, do I need to use two types of plaster?...One for the base to bond
with the lath and rest of the base and one for the finish surface?

And for cracks that might open up again, should I dig down a little and
bury fiberglass tape across the joint and below the surface?

Mike

my neighbor is a ACE patching plaster. He uses drymall mud, and taped a
crack here that forever returned That was 9 years ago and its
imnpossible to find it.

So try some drywall mud it dries slower so you can work it! Patching
plaster sets up so fast theres no time to do anything

my neighbor is a ACE patching plaster. He uses drymall mud, and taped a
crack here that forever returned That was 9 years ago and its
imnpossible to find it.

So try some drywall mud it dries slower so you can work it! Patching
plaster sets up so fast theres no time to do anything

Thanks for the advice.

The only reason I mentioned tape is that there's an crack that goes
from the ceiling to a wall and it was repaired before (and recracked).
I was thinking about routing a shallow channel on either side of the
crack with a chisel and setting the fiberglass tape (not the paper
drywall tape) in it so that it wouldn't recrack.

Also, is there any trouble getting finishing plaster to bond with the
top layer of plaster that's already there? I have some small dings,
like something sharp hit the wall and left a divot.

Mike

Plaster should really be used where the edges are undercut to help it
hold. For small cracks and dents and nailholes, spackling compound
would be a better choice, as it has some sort of glue in it and will
adhere better without the undercutting.

As to the recurring crack, I suspect the lath is not well secured, or
possibly the house is settling (not really likely in a house that old
unless there are foundation problems). I'm no fan of tape; if the
problem is unsecured lath, I would think you would end up with two
cracks, one on each side of the tape. I'm also no fan of mud, but it is
getting harder and harder to find real plaster; I went into Home depot
once and asked where the plaster was; they pointed to the drywall compound.

wrote:
Thanks for the advice.

The only reason I mentioned tape is that there's an crack that goes
from the ceiling to a wall and it was repaired before (and recracked).
I was thinking about routing a shallow channel on either side of the
crack with a chisel and setting the fiberglass tape (not the paper
drywall tape) in it so that it wouldn't recrack.

Also, is there any trouble getting finishing plaster to bond with the
top layer of plaster that's already there? I have some small dings,
like something sharp hit the wall and left a divot.

Mike

My experience regarding plaster repair is that it is not too
complicated
if you know what you are doing. In general, a crack is not going to
stay closed using the old "finger and spackle" trick. It needs
reinforcement, and that means drywall tape. Paper tape works fine
if you first clean the crack and prefill it. You want to make sure the
plaster surface is clean. You can embed and coat the tape with
multipurpose joint mud but setting type compounds are tougher.
Just use those with longer setting times and mix small batches
and you will find that it works well.
A good trick to keep in mind: if you are worried about getting good
adhesion over painted plaster, brush on a plaster bonding agent
over the crack and surrounding area before you tape. Let dry then
tape, coat etc.
BTW, a good website with lots of free info for fixing plaster:
www.plaster-wall-ceiling-solutions.com

wrote:
I need to do some repairs to my 53 year-old plaster walls. The lath is
metal mesh grid, which holds a sandy colored base. And the finish coat
(yes, there might be another layer between this and the base) is a
nice, smooth, creamy colored surface. I have a lot of patience and am
willing to do it the way professionals would if I have to.

I have some narrow cracks that I can dig out to hold the plaster patch.
Exactly what type of plaster is used here? Gauging plaster with lime?
Moulding plaster? The guy at my office who repaired the plaster walls
(and did a fantastic job) said he used lime and moulding plaster.

For larger areas, where pieces have broken away all the way down to the
lath, do I need to use two types of plaster?...One for the base to bond
with the lath and rest of the base and one for the finish surface?

And for cracks that might open up again, should I dig down a little and
bury fiberglass tape across the joint and below the surface?

Do yourself the favor and save the effort. This stuff is easy to use
and it works great. A good paint store will have it.
http://www.tuffkoteco.com/kkapply.htm

R

Not@home wrote:
I went into Home depot
once and asked where the plaster was; they pointed to the drywall compound.

They're just numbskulls. They do have it; it's over in the building
materials in 80lb bags.

Mike