Hi folks. Looking for some advice on repair of some old lime plaster.

Here's the background:

I live in a house built in 1791. All plaster is original to the house. Most is in fair shape.

Since we've been here, I redid one room using plaster washers and screws and then skim coated a wall using naturally hydraulic lime, which sets quicker than a slaked lime plaster. I got decent results, but even the manufacturer of the product didn;t recommend using it as a skim coat.

I have also plastered a bathroom using a three coat lime plaster, and that worked really well, but I was down to stone on the exterior surfaces and I installed new lath on the interior walls so it was a true three coat finish. Much easier to do than a skim coat(in my opinion).

Now I'm working in the center hall of the house. Allmost all the walls are interior walls which don't need to have moisture permeability of a true lime plaster, and all are in fair repair, so I'm wondering how to get them paint ready. The walls were formerly wallpapered, and prior to that is appears that they were painted with calcimine or distemper. In the previous room that I've completed, this was also the case and although I used a carbide scraper to remove the calcimine from those walls, I still have issues where the final paint is peeling and showing poor adhesion. (no adhesion issues where I skim coated things.) I even went back over those spots and rescraped down to the brown coat, washed with TSP and used a special binder in the paint, but the paint issues persisted, albeit less visible, but still there.

Back to the hall - there are some long cracks in the walls in some spots, there are former patches made with what looks like gypsolite or some other perlited gypsum plaster, and some areas where a ham handed electrician wasn't smart enough to fish a wire, so he cut a switch run into a wall. I don't need a full skim coat because there are large areas where the walls are fine, and I am ok that the walls show their age. I don;t need the finish to be smooth as glass and uniform across the whole wall. Also , if the skim coat gets too thick, it will cause an issue with the depth that some of the molding is set.

What compound have others used with success to repair this type of thing? Premix joint compound, quick set joint compound, actual gypsum plaster?

Should I use a mesh or paper tape over the cracks? Will plaster weld help things adhere or should I just wet the edge of the old stuff as I go along so it doesn't suck the patching material dry prematurely? I actually met a contractor that specialized in old houses and he indicated that he was using a full mesh covering of the wall and them skim coating over that mesh to ensure that no cracks would appear. I cannot recall what material he was using over hte mesh though.

I want to know what any pros out there have done with good results. I really want to preserve as much of the old material as possible, so a full rip and replace program is out of the question.

Thanks for any advice you can give.

I appreciate it/.

HB

"Dear, you can have quick, cheap or right - pick two....

 

Since I'm not well versed in plaster I normally use durabond to make plaster repairs. Our plaster pro should be along later so wait and see what he has to say

 

Hb2u, you have a variety of issues going on. Since you are in SE PA, you might find it beneficial to go to the "Historic Home Show" in Valley Forge this weekend. You will find at least one manufacturer there that may have products applicable to your situation.

I am a little puzzled by your reference to "scraping off the calcimine". Calcimine, to my experience, can be rubbed off with a wet rag. The whole purpose of the material was to provide a finish coat that could be applied over uncured plaster with the provision that it could be wiped off when the next calcimining was to be applied.

Have you been able to determine what the nature of the cracks are? If it is an ongoing structural issue then that should be dealt with before plastering.

I have done a variety of overlay applications. Usually I try to stay as true to original as possible.

I have used the fiberglass mesh approach with plaster-weld and veneer plaster base coat with a traditional putty lime finish coat. I have also done the mesh with a double coat of dura-bond joint compound. The first coat would be reinforced with fine sand and the second coat would be hard troweled with a spray of water. You can develop a finish that is close to traditional putty coat plaster finish.

There are lime products that can be applied in skim coat form over your existing material except for the calcimine issue. I'm not sure that there aren't some that can be applied over the calcimine. Again, this is not a dead industry, so new materials and methods do come about. I would still suggest a visit to the show this weekend.

 

Thanks for the input Calvert- I actually received a discount admission ticket to the home show this morning from the Degruchy masonary website.

I don't know if it's in the cards to go this weekend though. I've got three kids under the age of 5 and they're all a bit under the weather the past few days. I'm going through kleenex like a frat house goes through beer cups...

Anyway, here's what the calcimine looks like. It DOES NOT come off with a wet rag as all the articles I've read say it should. I have been after it with a scotch bright green scrubbing pad and it takes forever and a day to scrub any of it off.

It does seem like calcimine in that it degrades to a chalky white slurry with scrubbing, but it is well adhered to that wall.



The cracks are from age. The house was built with green timbers (I'm guessing) and they've settled over time. There has been no movement in the 14 years we've been here and it's not water damage.

Here's some of the cracks:



What kind of lime putty finish coat are you putting on? Are you slaking you own type S lime or do you have a supplier for quicklime? Does your lime putty finish coat use plaster of paris in it?

Thanks for the input!

HB

 

I it has been a long time since I looked but I think if you do a search for "Repairing Historic Flat Plaster". you will find the publication by the National Parks people that deals with the various materials and techniquesx for what you have in mind. They Are. Alex "Preservation Briefs".
to remove th Kalsomine try as strong vinegar solution. Maybe, just maybe if the Kalsomine was applied while the lime plaster was still green it may have cured right into the plaster. I think if you can't get e kalsomine off by hard scrubbing maybe it is bonded well enough to leave it.
Also do some looking for lime based Venetian plasters and talk to some of the folks at some of those companies. they can be a lot of help.

 

Thanks for the input. I read about using vinegar to loosen the calcimine, but that would also dissolve the lime in the top coat of plaster wouldn't it?

 

I figure the plaster is more durable than the kalsomine
probably you should rinse with clean water fairly quickly

 

I agree with tightcoat about the fact that if it is that well bound to the plaster you should try a test patch of new finish to see what issues evolve.

If you have not already found " The Master of Plaster" products you should look it over and call them. I got samples a few months ago and will be trying it soon. They have a user/distributor in NJ who is very helpful over the phone and will even come to your house to help with the job should you be so inclined.

Also, have you investigated the "Takcoat" product from Degruchy?

 

I was holding out to see if I would have the chance to stop in to visit the Degruchy booth at the home show to ask in person, but it looks like I'll have to call him next week.

I am going to experiment with an adhesive repair this
weekend. I'll post back on how it goes.

Thanks!

Hb

 

hb2u, I was at the home show yesterday and spoke to one of Degruchy's reps.. He felt that the Takcoat product would work as a base material and if you have a lot of cracks to embed the fiberglass mesh into the material and trowel over to bury it. After this has set you could apply the "Ecologic Topcoat " material they sell. That is available in a coarse, fine or extra fine aggregate version depending on your needs.

Of course if you get to the show you will find them available for discussion or as you stated call and verify the procedure, although everything seems fairly straightforward to me.