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patching water damaged plaster on fireplace


Bruce-31's Avatar
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05-04-04, 06:12 PM   #1  
Bruce-31
patching water damaged plaster on fireplace

I have a old house with a rock fireplace[pre-1930's]. Water has leaked in and damaged the plaster that is covering the fireplace. The paint-covered plaster has cracked and bubbled to the point that I have no choice but to patch several big holes in the existing plaster. I have a good bit of experience in drywall and plaster repair but I've never had to repair over a fireplace. I've had to go close to a inch in depth in some places and attempt to build it up form there with joint compound. I'm encountering what I thought was a cement-like substance under the plaster. When I tried to clear away any loose debris with a wire brush it just wants to crumble under the force of the brush. I tried to vacuum the holes and gently apply a layer over this mystery substance, but, when the first layer dried, it pulled away from the wall. I guess because it wouldn't adhere to the sand-like material. The material I've encountered isn't falling down or crumbling to the ground, I would just like to know if I need to go deeper and maybe encounter some former backing or is there something I can put over this substance to seal it and make it able to hold the patching agent

 
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coops28's Avatar
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05-05-04, 06:32 AM   #2  
You need to remove all loose material and get to a solid base and work back from there.

 
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05-05-04, 07:25 AM   #3  
I agree with coops, mud will bond to most surfaces, but not to something sandy in nature. Going to have to strip down the wall further until you get to something solid. Good luck!

 
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05-06-04, 04:17 AM   #4  
Bruce-31
Need feedback on my experiment with spray paint

Thanks for the input guys. I knew from experience in the past that you must have a reasonably sound,dry, and debris free base for any mud or patching material to adhere to. I guess I was looking more for information on what the material is. I talked to some guys who said it probably is some kind of mortar or cement-like substance( he mentioned something called horse-hair cement) although he said my house probably isn't that old. But check this out. I was a bit reluctant to keep going further back to find rock-solid material to mud over so I used a can of old spray-paint to bind the gritty stuff together. I just sprayed the trouble areas good and waited for it to dry and recoated the same areas. Then I put about a 1/4" of mud over it and let it dry.Then I came back after it had dried and did it again. It seems to hold pretty well.
Thanks for all the advice. I'll write back before I paint to report on the end result so wish me luck!!!!!!!! Also write back and tell me if you guys have ever tried anything similar to this or have ever heard of this being done before.

 
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