My husband is planning to use joint compound to patch our plaster walls.  I recall reading somewhere that this is not a good idea as they are not compatable or something.  Also, I hear a great deal about Master of Plaster and how it will stick to any surface.  Is this to say that other products will not adhere to paint, etc.?  Finally, I would like to skim coat the walls but have NO experience.  Is it difficult to get a smooth wall surface?

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Try a wall in a closet if you want to do it yourself.  If you can make that smooth, then great. If not, only the inside of a closet will have weird waves in it, and no one looks at such walls.  I speak from experience, because I have done some pretty shoddy work on the walls and ceilings of some of my closets.  They were untouched when I bought the house in 1995 with original horse hair plaster and original paint on the plaster, having never been wallpapered.  Lots of crumbling and water damage for me to practice on.
My last house I hired a plasterer to skim coat the walls after all the paper was removed.  Some of the workers made some bad gouges in the walls.  He rolled the walls with some kind of sticky adhesive type paint, don't remember the name. After that he skim coated the walls and ceiling with something called "Hamiltons soft top" mud.  It came in a box and was yellowish.  It was great because it was soft and didn't need sanding,he just washed it with a sponge so no dust.  Once it was primed it was as hard as plaster.  I lived there for 14 years and never a problem.  Since I left the new owners stripped the wallpaper I put up in 1 room and said it came off and they had no problems. That means 24 years with no problems, you can't beat that.
Thanks for all your input!  Still not sure what's best to fix that cracks with, but Hamilton's sounds good.
Erin, I make my living teaching and consulting about traditional building materials and craftmanship. Your walls are likely a base material of calcined gypsum or lime. Because the walls are an old school material its very hard to get modern materials like joint compound with its glue and talc to bond with the older natural material that hardened over time by an air drying and absortion of CO2. Virginia lime works specializes in making repair materials that will bond in the old cracks and also keep your walks authentic. Jeff Price is the director of sales and these folks are the go to people for period lime materials for brick, stone and plaster prior to the advent of portland cement and drywall around 1917. The other method you mentioned is similar to what I had to do to my 1940 bathroom once the wallboard was stripped. All the damaged gypsum was sealed and consolidated with Zinsser Gardz and then skim coated with a blend of Plus 3 and mildew resistant latex paint. I used the new extra thin fiberglass tape over the dynamic cracks and the rolled out the skim coat with a good roller and finally smoothed out with a 14 taping knife. Great results! The rest of my house is 1860 lime plaster that gets treated with period materials. Cracks get sealed with a very special blend that goes back thousands of years and in our modern times is referred to as DHL lime injection. US Heritage in Chicago is the supplier. If you chose to use it I can give you some tips to make it come out well. Happy plastering knowing you are working with an ageless material of the highest skill level.
Thank you.  I'll look into this.  I don't have a lot of confidence in my skill level - none.  I guess I have to start somewhere.  No comment on the Master of Plaster?  Also, I've heard Big Wally's is the way to go to re-attach loose plaster to the lath.  Any experience with this?
Hamilton's just sounds like a brand of standard drywall compound ("mud").  Mud stays water soluble forever and can be smoothed with a damp sponge at any time after it dries.  Once painted, it's nearly impossible to tell painted plaster from where it was skimmed with mud.

I have no idea what any of you are talking about... I have had absolutely NO problems whatsoever using standard drywall compound ("mud") on any of my plaster walls over the last 21 years.  Some areas over bare plaster, some over old paint... no peeling, no chipping, no flaking, nothing.  There is no reason why "mud" wouldn't stick to a clean plaster surface (it even sticks to wood).  Areas with gouges down to the base coat I've filled with "mud" and had no issues at all.


The best part about drywall compound is that it's 100% NON-destructive.  If you think you ruined something, simple water or steam will remove the mud no matter how much time has passed.  However, try making your patch with plaster without enough skill or experience... no amount of sanding, water, or steam will undo that mistake... just get out the hammer & chisel.


And finally, the compound's ability to remain water soluble makes it very easy to work with even after it dries.  A damp sponge is a dust free way to re-smooth the surface.

Thanks for commenting.  I hope you're right because my husband went ahead and used it anyway.  I guess time will tell.  I appreciate everyone's input!

I'm sure you'll be fine.


I can only see it peeling, chipping and flaking if the original surface is peeling, chipping and flaking.

Did you use drywall compound that was premixed - out of the bucket, or did you use the powder setting drywall compound that you mix with water and has a certain set time? 

I am trying to figure the EASIEST but still effective way to just smooth over my bare horse hair (1900) plaster walls. I have done both of the above in my hallway. I just scraped it on... to fill the inconsistencies... but texture still shows through. The premixed product seemed to work the best, but it gets the most negative rap for longevity (though no one has said it has come off for them). The setting kind was difficult at such a thin application as it dried in spots before it ever activated (heated up) and hardened. So  I ended up with a patchwork of set and not set compound on the wall. Because I had put it up on a very awkward area (ladders., stairs, ) I just let it go, primed, painted, and hope it lasts as long as I am here. But I have 3 more rooms to go. 

So, premixed, or powdered setting type compound? Or something else? 

In additions, I have two areas about 1 ft square that need extra (1" deep) fill.. Can I still use either for these? I thought of using the setting compound to build up the level. The the premix for the top surface of all. 

Cured lime-based plaster does not have an affinity for gypsum. So, the worst case is using pure plaster of paris to lay a new white coat over an old lime brown coat where the original lime white coat has fallen off (due to water or physical damage). That repair has no chance of lasting.

At the opposite end of the spectrum, fixing a divot in the wall prior to repainting, almost 100% chance of success.

In the middle, where most real world repairs are, there are much better ways to remedy cracked plaster than the easy mud & tape, quick and dirty. And there are no shortage of articles and opinions.

My material list contains Bonding agent, to mop or spray into the cleaned cracks; Durabond 90 (setting-type joint compound mixed from a powder). Various compositions and shapes of corner beads and tapes. I like the metal-reinforced paper inside corner beads where inside corners are really separated. I like the new fiberglass mat tape. For topping I use Easysand or regular green lid mud. I avoid blue lid mud and the dustless mud.

The procedure is to clean out and open up cracks that have movement. Cracks that have not moved (spiderweb type) will not benefit from opening up further. If plaster has lost its keys into the lath (sponginess) or is severely de-laminated, you will need to use lots of plaster washers or the Big Wally's system. After mopping (sponge) and/or spraying bonding agent into the cracks, pre-fill them with Durabond and scrape level to the old topcoat. Do not mound the mud on. When this "blocking" is done, you can bed whatever tape you have chosen to use with the durabond, mixed a little thinner than peanut butter. As wet as you dare, but so it still sticks to the trowel. If there is a large network of cracks and voids, consider the very wide sheets of sticky fiberglass mesh, that will save you from a melange of many small strips of tape. Work quickly, or the mud will dry and the non-mesh type  tape will blister. Work in that tape or bead firmly and squeeze out a portion of the wet mud from under. This is a signal that it is not too dry. Do not topcoat the tape until its bedding has dried hard. After that, it's basic mudding 101, and feel free to use normal green lid premixed mud unto completion. Let everything dry out hard before priming, if it's clammy and cold, it is not ready. This takes longer in winter; a small space heater can help.  HTH


*Just realized this is an OLD thread...maybe it will still help someone out*

We also have had no issues skim coating with drywall mud.  We've used it all over our house to skim coat walls, ceilings, stubborn old wall paper (which was taking all the plaster with it) and level textured ceilings.

As for the crack repair:

I just finished repairing a badly cracking and detached ceiling in our parlor.  There was decorative plaster moldings and medallion in the room, so we really wanted to save the ceiling.

We checked out the Big Wally's system, and while I'm sure it works great, it was expensive.  After a lot of reading, we came up with our own solution that was inexpensive and appears to have great results.

Supplies: 300 sq foot ceiling with 80+ linear feet of cracks <$100 for all supplies

Box(es) of 1 3/8'' (or whatever you need) drywall screws

Tube(s) of Liquid Nails Heavy Duty Construction Adhesive or Subfloor Adhesive

Caulk Gun

A lot of plaster washers (our local hardware store had these, 100 for $10.)

1-2 3/16'' drill bits (they'll get dull, you may want more than one depending on size of project)

Power Drill

Drywall tape or mesh

Drywall compound

First, we got a 3/16'' drill bit and I spent two days drilling 700-800 holes in the ceiling, spaced about 2-3 inches apart on either side of the cracks.  You want to make sure you hit lathe with the hole, this will be important later.  We made sure we marked the ones that didn't hit lathe to avoid confusion and wasted supplies later.  We also drilled holes where the ceiling was noticeably detached from the lathe, but had not cracked yet.  

Then, we vacuumed out as much dust as we could from the holes and I sprayed water into the holes we'd be working on, only doing small sections at a time to slow the tack time of the Liquid Nails.

Next, inject Liquid Nails into each hole until it starts to come back out at you or comes out another hole.  You want to make sure that you're injecting between the plaster and lathe and not just up the keyway.  This is where marking the holes that don't hit lathe comes in handy.

Then, take the drywall screws, place a plaster washer over and slowly compress the ceiling until firmly on lathe.  There isn't a specific pattern to this.  In some sections, we felt it necessary to put a screw/washer in every hole.  In others, we would leave a few open in between depending on how loose the ceiling felt.

Next, wipe off excess Liquid Nails and allow to set for 24-48 hours.  Then, come back, remove screws/washers and fill holes and tape/mud cracks.  Finish sand.  Paint.  Done.

The pictures are of the parlor after finish sanding, then paint.  The other one is the same technique being used in my foyer (don't have access to the in process parlor shots at the moment).



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