Botched repairs over cracked plaster

Anyone out there still know anything about repairing plaster walls? I have a 1920s home that had and still has in some other places cracks running up the walls and branching out. I've already had the foundation checked and it's ok, but inside they look terrible. Apparently just old settling. We just bought the home and the prior owners had tried to patch the cracks by it looks like putting one of the mesh drywall tape all over the cracks and spackling either drywall putty or plaster all over it. So it not only looks bad, but basically, the cracks were just covered over by about 1/2 inch thick compound that is bulged out from teh wall, that only draws your attention to where the cracks were and looks terrible, and in some of the repairs, the cracks are just coming back through the repair. I had our general contractor look at it and his solution was to tear the whole wall out and sheetrock it, which seems to be the only thing that most construction guys know these days, but it won't match the texture of the other walls, and I would like to keep the lath and plaster where ever possible in the house. My questions are: 1. If I sand the repair job off, how do I do a lasting repair that won't crack again and will look good? Someone suggested that I dig out the plaster along the crack after sanding, use drywall tape (solid tape, not mesh) and treat it like a normal gap in drywall. 2. Should I just bite the bullet and drywall the entire wall and forget about the plaster? Thanks so much for any information. Best Regards, David
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David:
I went through the same thing with my 1930s house. I wanted to drywall the whole thing, but my ex felt otherwise because all the shexpert newspaper columnists said "plaster removal is really messy". Yeah. No kidding. :-) They also said putting your hand on a rotating circular saw blade could ruin your weekend.
Fortunately, I had a hardware store two blocks away whose owner was apparently one of the last humans in this city who knew how to handle plaster. He suggested what's already on YOUR walls - the mesh tape, but covered with plaster, not drywall compound. The repairs done based on his instructions have lasted about 15 years so far. In your case, you'll have to add "Remove old mesh tape". Although you may have worse settling problems than other houses, let's assume for the moment that you don't, and assume your cracks returned because of bad materials, bad technique, or rushing the drying process.
First of all, find REAL plaster, not drywall compound. I haven't shopped for it in ages, so I have no idea if the big home improvement stores carry it. You may have to hunt down a smaller hardware store. You'll also need 2-3 sturdy plastic trays. You'll find out why later. You'll need a shop vac with a spare filter, and plenty of replacement bags. A second hose is a good thing. You can hook it to the exhaust and put it out the window so the vacuum doesn't blow around the dust that's at point B (behind you) when you begin vacuuming point A (in front of you). You'll want to keep the filters clean. They clog quickly, and the dust will raise hell with the vacuum motor. Some can be washed. Keep up with that task so they're dry when you're ready to continue the next day.
1) Open all hairline cracks to 1/4", even if you don't think they need it. In my house, some hairline cracks were just waiting to become wider ones, with loose plaster beneath, so all I had to do was sort of scrape them with a screwdriver blade. For some, I put on a mask & goggles and used a cylindrical Dremel bit. If, after widening a crack, it seems like the plaster's not adhering at all to the lath, widen it more.
2) For wider cracks, clean out all loose debris with whatever tool does the trick. For all cracks, finish by vacuuming out dust & fine debris. The best shape to strive for is an inverted "V" into which you can wedge the plaster as it's applied. Not that hard to do if you angle your destruction tool the right way.
3) The depth from the surface to the lath may be inconsistent from place to place. Where it's greater, you'll have to apply one or two initial layers of plaster and let them dry before you apply the tape and the final plaster layer. For the initial layer on wide cracks, try and press the plaster into the gaps between the lath, just like the original stuff. That helps it adhere. Color, feel and smell will tell you when it's dry. In my house, some areas took more than a week, especially on colder, outer walls.
4) Apply mesh tape by using your finger to "indent" the mesh slightly into the crack, maybe 1/8" deep. Then, flatten the tape onto the wall either side of the crack. If it won't stick, the wall's probably dusty. Vaccum it better. Obviously, don't create dimples by trying to make turns with the tape. Cut it into sections. Be precise, trying not to leave gaps between pieces of tape.
5) Use a spray bottle on its finest mist setting to dampen (not soak) the crack before plastering. If it gets wet, dab it up and wait a bit. It'll take forever to dry if you leave too much moisture. Use an even LIGHTER amount of mist to moisten first-coat layers before applying the second coat.
6) Mix small amounts of plaster. It begins getting warm and setting within minutes, especially if you mix it too much with the application tools. Experiment by mixing a cup of it first and just playing with it so you have an idea how fast you need to work. Initially, I found myself throwing away half of each batch because it became what potters call "leather hard" within 10 minutes or so. This is the reason for multiple trays. When the plaster you're working with begins hardening, just put down the tray and mix the next batch in another. In 1/2 hour, invert the first tray over the trash can and smack it to remove 99% of the plaster. No clogged sink that way.
7) Wait for it to dry. If it feels cold, it's obviously not dry. You'll figure it out. It'll also smell different when dry. Depending on depth and humidity, it could take two days to a week.
8) For sanding, buy the black sanding sheets - the mesh kind. With the plaster I had, the dust was pretty heavy. It fell through the sanding mesh and straight onto the floor, rather than floating around in the air. Not as messy as I thought it would be.
Other tips:
Serious: - Before working on each wall, place the palm of your hand on the wall in various spots, especially around the cracks, push and listen. In some spots, you'll feel that something's wrong. In others, you'll hear what sounds like large amounts of debris falling inside the wall. If you sense that the plaster has separated from the lath by more than 1/8 to 1/4", forget trying to fix just the cracks in that area. The repairs will not last. It's time for fun. Use the heel of your hand and slam the wall until large chunks come off. You're better off repairing areas the size of serving platters (or dinner tables) than returning to the same cracks a year later. Do this push test BEFORE you begin any work. Because you'll be applying very large amounts of plaster in these areas, you'll want to do them first so they have time to dry. A month is about right, since large areas require multiple applications to build up thickness.
- If anyone has dreams of ceiling fans or other electrical toys, now would be a really good time to rip out electrical boxes and replace with new ones, or just to rewire whatever you can. Take a good look at your wires, since you'll have switch plates off anyway. If they look old and crumbly, they ARE. Got a single-switch box in a room? Change it to a double, drop a spare wire into the basement, label it, and put a one-side-blank switch plate on the box. You never know. If your wife isn't sure about recessed lights or whatever, pay to have her tested on a polygraph machine.
- This could take months. Stop buying beer by the case. Buy kegs.
- If your wife thinks this is a better idea than you do, milk it for all it's worth if you're the one doing most of the work. And, begin discreetly asking YOUR friends if they know any good marriage counselors.
- What you called "texture" has another name: Decorating befuddlers. It's bad enough old homes have no right angles to speak of where various surfaces meet. What a great idea - adding ripples so that wallpaper or moldings are even harder to install. My ex hired a guy to hang our patterned wallpaper in one room. He said it would be easy. I was home for vacation that week. The guy was close to tears. :-)
- That reminds me: If anyone has ideas about tricky molding & chair rails, install them AFTER PLASTERING, BUT BEFORE YOU PRIME. It's not easy to create a flat plaster wall. You'll need to fool around with plaster & putty AFTER installing molding, in order to fill gaps and create the illusion of perfection.
- A really big straightedge is a good thing to have for this project. You can use it to check for what appear to be bulges in long expanses of plaster wall. Sometimes the light plays tricks and you THINK you see a stretch of plaster which has separated from the lath. Sometimes you're right. Or, if you have to repair huge sections of wall, you can monitor your sanding technique so YOU don't create bulges. If you don't think they look so bad after sanding, believe me, they'll look outrageous after you paint them, and especially if some crazy person chooses wallpaper with any sort of linear pattern.
-Doug

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I agree with everything here except use of tape. Get a bag of perlited gypsum plaster (known to the old timers as brown coat) and use that for your first coats (unfortunately, it usually comes in very large bags). Get some finishing plaster, often called patching plaster, and use that for your final coats. The final coat should be about as thick as very thick paint, and it is pretty easy to get that smooth to the point where little sanding is needed. If, in the course of getting down to solid plaster, you end up with large areas you will have to do, I would suggest finding a real plasterer, as there is a lot of talent involved in doing larger areas, and corners. Around here decorators usually seem to know someone who can do real plastering, although there are fewer and fewer of them left.
Doug Kanter wrote:

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Interesting....some of the old plaster in my home was darker near the lath than at the surface. Maybe that was the brown coat you're referring to.

True. There used to be a small group of architects in my office building. One of them was involved with redesigning a local office building lobby, and it required some fancy texture plastering. Because they couldn't find anyone local (Rochester NY), they ended up hiring a bunch of guys from Florence, Italy. They were just slightly more expensive than people from the NYC area.
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David wrote:

I bought a home build in 1910 and many of the walls appear to have drywall over plaster. When I was correcting some of the outlets with hot/neutral reversed, I noticed extenders to bring outlets and wall plates to the drywall surface. I figure this gives the home thermal mass, so it maintains an even temperature when heated by steam, and does not heat up so quickly on summer days (suck the heat out with a fan at night, so A/C is rarely needed).
There are things that can be applied to the walls to give them texture. When my sister build their home in the late 70's they used something pigmented applied with a rag or sponge that gave the drywall sort of a stucco appearence. So even if it got chipped or worn, it would still have the same color.
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