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Old 01-06-2018, 07:23 PM   #1
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What was done to this plaster top coat? Trying to replace it


Going to have cabinets put in soon, and upon taking down and old cabinet a large chunk of a top coat type material cracked and fell to the floor and exposed what looks like good condition plaster. This used to be a rental unit, and it looks like the previous owner covered up some old imperfections from prior tenants - plus this used to be where the stove was (heat and humidity probably took a toll)

The coating was "floating" and didn't feel like it was adhered to the plaster, and cracks were there from movement with more likely to come . The pieces I took off had a dark and light color - as if it were two coats of different types of compound.

I took it all down, sanded the old plaster wall cover, and am going to patch the old holes.

My question is: what exactly was done to this wall to start? I took a picture of what I took off of it. Is skimcoating and feathering to the secure portions OK to do? Finally, should I use some sort of primer on the plaster cover to prep for the skim coat?

Pictures attached



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Old 01-06-2018, 08:01 PM   #2
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Re: What was done to this plaster top coat? Trying to replace it


It appears that a bonding agent like Plaster Weld was used over a painted plaster surface & than a Setting compound / Joint compound was used to top coat the existing plaster. Also in the photo the top coating appears to be about 3/8 inches in thickness which is to thick for a setting / joint compound. The use of a drywall product over a plaster product will over time cause failure due to moisture. The reasoning is Plaster can hold moisture with little or no effect were as drywall products can not take the moisture and a separation will occur . I know of only one product that will bond to the existing painted plaster that will not fail. It is a veneer plaster topping but it should be limited to a thickness of no more that about 1/8 inch in thickness. USG hand book also states that Sheet rock joint compound not recommended for interior plaster & masonry subject to moisture. For a repair you can look at using some of these products.
TexSton
American Clay ( on this one watch the moisture statement )
Variance veneer plaster
Master of Plaster ( this is my proffered product )
There are also many others on the market which i have never used.
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Old 01-06-2018, 10:49 PM   #3
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Re: What was done to this plaster top coat? Trying to replace it


Wow thanks for the details on this, very appreciative!

Quote:
Originally Posted by ClarenceBauer View Post
USG hand book also states that Sheet rock joint compound not recommended for interior plaster & masonry subject to moisture.
So I wasn't clear in my original post, but this area going forward will no longer have a stove against it, just cabinet and countertop pushed against it. Since it will no longer be exposed to moisture, would joint compound work in this case or still not?

I was also considering a primer before covering it with compound/the other solutions - like Rx-35
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Old 01-07-2018, 08:33 AM   #4
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Re: What was done to this plaster top coat? Trying to replace it


On the question of will joint compound work i am not a fan of drywall products used over a plaster product. If you can not find a good Veneer plaster that will work over the painted plaster than you could use a setting type compound. For repairs over existing try to keep the repair material from 1/8 inch to no more than 1/4 inches thickness. As for a bonding agent i have used Peel Stop worked very well for the very BEST look for BA57 bonding Agent from Master Wall. If another type bonding agent is selected MAKE sure it is NOT Re- Emulsion able. You will also need to plug the holes before a plaster coating is applied. From the photo that corner bead was used up until about the late 1950's I have not seen one in the last 30 years.
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Old 01-07-2018, 06:07 PM   #5
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Re: What was done to this plaster top coat? Trying to replace it


I see you have a pipe going up vertically along the corner. So this area will be covered up by cabinet up top and bottom, with only a smaller mid section exposed?

It may be easier to locate the framing behind the plaster, put in a few 1/4" thick furring strips, then mount a 1/4" plywood sheet over the whole thing instead of struggling with the plaster.
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Old 01-07-2018, 09:14 PM   #6
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Re: What was done to this plaster top coat? Trying to replace it


Quote:
Originally Posted by ClarenceBauer View Post
On the question of will joint compound work i am not a fan of drywall products used over a plaster product. If you can not find a good Veneer plaster that will work over the painted plaster than you could use a setting type compound. For repairs over existing try to keep the repair material from 1/8 inch to no more than 1/4 inches thickness. As for a bonding agent i have used Peel Stop worked very well for the very BEST look for BA57 bonding Agent from Master Wall. If another type bonding agent is selected MAKE sure it is NOT Re- Emulsion able. You will also need to plug the holes before a plaster coating is applied. From the photo that corner bead was used up until about the late 1950's I have not seen one in the last 30 years.
I went ahead and took the setting compound routed and did Durabond with the Peel Stop as prep (sanding the paper to get some better adhesion). A lot of waves and lines from my first time doing this. There's only going to be a small part visible after the top and bottom cabinets go in though. I'm going to sand what I can, even though I know Durabond is tough to sand and maybe spot repair a few other areas to finish before painting. I know plaster is harder to handle, and even though my work is not so hot with the Durabond, I knew it would be the same with Plaster and I wanted the ability to sand - thank you for your help!
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