Joint compound/sanding questions


Is joint compound the right material to patch old walls of plaster and lathe that have cracks from the house settling?
What happens to joint compound if it freezes/thaws a few times? (Not long term freezing, probably just a day or two.) Is it best to discard it and buy more or is it still usable? This is an unopened 42# container that got left in an unheated part of the house.
And after we get over those hurdles, what's the best way to sand the walls after patching? Belt sander? Orbital? Any sandpaper grit suggestions? The plaster at the edge of the cracks is slightly peaked outward and we want to gently sand that down as much as possible without causing BIGGER problems.
Thx.
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wrote:

I seldom use joint compound on the restoration of my 1930 home. The stuff sucks, it's water soluble....just add water & it turns to mud again, it has no strength or flexibility but it is cheap.
How old is the house? Obviously you are located where the weather can get pretty nippy. Has the settlement ceased? Are the wall smooth or some sort of texture? (I've got some smooth / some textured) Cracks only or loose / missing plaster / loose plaster?
I use different techniques depending....
textured walls with cracks get vac'd & a flexible caulk worked into the crack, sponge work to minimize the caulk down to the crack only. IMO a single smooth line on textured wall looks better than a wide swath of smooth mushed over the texture.
Smooth walls get patching plaster, good knife work will minimize the need for sanding.
Why does "The plaster at the edge of the cracks is slightly peaked outward...." ?
Is the plaster loose from the lath?
If it is loose, you need to remove & replace unsound section or attempt to re-adhere it. I have successfully injected liquid Bondo or epoxy through small holes drilled in the plaster & then jammed the plaster back up against the lath with a "wall to wall" strut. The stuff has held for YEARS. This only works if the plaster keys do not prevent "fit up".
Otherwise, chip out bad section; scratch coat, brown coat, finish coat.
Sanding sucks, try to minimize the need. A belt sander can remove a lot of matl quickly; which is good & bad. But you can always use patching plaster to get the surface back again if you gouge it.
I wouldn't risk using the frozen stuff....is $25 of mud worth your potentailly wasted time if the stuff is bad? But I hate the stuff anyway so take my advice with a grain of salt.
I used some really old patching plaster last week; too cheap & lazy to drive to the store......but I did test it, the stuff kicked in about 5 minutes but never really gained strength.
Luckily I didn't use on the repair first. I used some interior / exterior spackle instead to fill in some small imperfections around a ceiling light install.
cheers Bob
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Around a 100 years old.

Central Indiana.

We assume so. I'm helping a friend who bought the house a few months back. The cracks are in the oldest part of the house.

Well, I *think* they're supposed to be smooth but that's probably just an ideal that was never achieved in the original plaster work. The ceilings have me a bit more concerned since they look a little rough (but not a stucco look) and they have fine cracks running the width of the ceiling about every 2' or so. It almost looks like wallpaper but I'm pretty sure it's just plaster up there.

Cracks only -- although there a crack down one corner that's maybe 1/3" - 1/2" wide.

Any particular type of caulk?

Hard to explain and I don't have enough experience with old plaster to explain it any better. The edges are sort of raised outward toward the room. If you ran your hand over it, each side of the crack edge would be the first thing that your hand came into contact with. I assume that's just decades of humidity/drying making the plaster sort of curl at the edges. ??

It doesn't seem to be. Everything seems solid except for those cracks. When we actually get on ladders and start working with those cracks, though, we might get a nasty surprise, I suppose.

I think THIS part is where I'll tell him he needs to call in a pro. I've done a bit of house repair but this is beyond where I want to go. Hey, I'm just a girl. ;)

So you'd recommend a belt sander? For versatility around the house down through the years, which sander would be more valuable to have? It'll be his first power tool purchase and he'll want one that will serve well for a variety of jobs, I'd suppose.

It's gone then. I'm pretty Scots about this stuff but I'm not wasting my time on something that might cause me more work in the long run.

Thanks, Bob!
About ready to start tackling this, Giselle
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On Jan 28, 10:54 am, FragileWarrior

Sorry about the slow answers.....DIY'ing it today
........Any particular type of caulk?
I use & recommend PolySeamSeal, I have had very good luck with this product.....others in the ng don't like it so much. I live in SoCal & it works for me but for interior work even in the mid west anything is probably ok. Water clean, smooth with a wet finger or sponge.
..........I've done a bit of house repair but this is beyond where I want to go. Hey, I'm just a girl. ;)
No worries, even a girl can learn this suff.... j/k
here is a great little blurb if you need / want to get into plaster repair
http://windsweptsoftware.com/myhouse/plasterrepair.pdf
the plaster in my house (1930) appears to have some sort of natural fiber (horse hair?) in the first or second coat. I've been lucky haven't had to do much repair....sometimes I use a structural epoxy paste.
www.abatron.com but it's kinda expensive and towards the overkill end of the spectrum but the stuff is strong & I have a 20 year history with the stuff.
If you really want to go nuts checkout this paint I used on my house's exterior trim
http://www.solventfreepaint.com /
organic linseed oil, no solvent, linseed soap cleanup
works best on bare wood
About sanders.... I have a belt sander (3 x21) , a couple of palm sanders, a 4.5" angle grinder w/ sanding disc
My suggestion...instead of babying the raised crack, I have a go at it with a belt sander or an angle grinder setup for sanding. Grit? Maybe 60 or 80 with a light touch....but if the plaster is soft BE CAREFUL & try 120 or 100.
In any case you can always bring it back with a little plaster.
I like the Porter Cable belt sanders, mines a little small but I get into less trouble that way. Makita palm sander & DeWalt or Milwaukee angler grinder. Ebay is good source for used tools.
cheers Bob
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Maybe.
Throw it out. At about $10 it's not worth the risk.
I presume you're talking about ready mixed. Instead get the setting type, not the lightweight stuff but the real thing. It comes in various grades and if you read the bag you'll see that the most popular one "90" has an open time of 60 minutes. Much better than patching plaster or Plaster of Paris. Setting type compound cures by chemical reaction like concrete not by evaporation as does the ready mix type. It forms a very hard surface and can be used to fill deep holes like your crack. However only bring it to just below the surrounding surface and finish it off with ready mix (not the lightweight stuff).
If you want to do a really long lasting job coat the inside of the cracks (after appropriate excavation to solid plaster) and the lath with Plaster Weld. This is like a glue which stabilizes the current plaster edges and helps the new plaster/jointing compound adhere. Then when you're near the top usually just before the ready mix, layer fiberglass tape (joint tape) over the entire crack. Then apply the finishing compound.

Grrrr! No machine sanders! The dust will be terrible and you shouldn't need them anyway. Between each coat run the scraper across the surface to remove nibs and ridges. If it's really too hard and you've really screwed up and have to remove lots of compound they sell a steel mesh on a wooden block that you can use to take lots off. Don't worry about the gouges; they'll be filled with the next coat. They also sell (paint department) sponge blocks with fine and medium sandpaper glued on for the final finishing. They work well but you really don't need much. For ridge removal the carbide tipped scrapers (Sandvik; expensive) used usually for floors work like a dream.

Break them off. It's almost always easier to patch than to sand or scrape these old pieces.
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