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  1. #1
    Join Date
    Dec 2009
    Posts
    1

    Default Old Plaster on Stone Repairs

    We bought a two-story 1870s historical building that has stone walls and what appears to be horse hair plaster holding them together. The plaster is crumbling, which is a little scary structurally. It's not an option to remove all plaster and start over. What can we do to seal what's there and reinforce it without much current structure for the new plaster to grip to? Is there a clear coat or something to harden it?

  2. #2
    Join Date
    Aug 2009
    Location
    Ladson,SC
    Posts
    192

    Default Re: Old Plaster on Stone Repairs

    For starters plaster is NOT STRUCTURAL it is a cosmic.
    The structural part would be the mortar holding the stone in place.Does the plaster failure follow the mortar joints?
    IT sounds like there is a moisture problem.Keep in mind that there are two natural things that cause plaster to fail WATER & FIRE.Check the mortar joints on the exterior for signs of failure.
    Being constructed in 1870 I would think that the joints are a lime sand mixture? If this is correct than anything containing portland would cause further failure at a very slow rate.
    Do not apply any sealers or any mixture that is higher in a PSI rating than Maybe a type O mortar this mortar should test no higher than 750 PSI.
    I would have a Lab test the existing material for make up and match the existing.For repair products check the following;
    U.S.HeritageGroup.Also Virginia Lime Works ( ask for Jeffery Price )The above will also test the existing material.

  3. #3
    Join Date
    Oct 2013
    Posts
    4

    Default Re: Old Plaster on Stone Repairs

    [IMG][/IMG]

    How do you fill voids behind plaster? When I tap on the walls, I can hear where it is no longer attached to the limestone. Will the glues and "goo" used for lath and plaster repair work on stone?
    Last edited by Cawker City Museum; 10-02-2013 at 10:33 PM.

  4. #4
    Join Date
    Oct 2013
    Posts
    4

    Default Re: Old Plaster on Stone Repairs

    [IMG][/IMG]

    I am just getting started restoring the plaster in our little museum. When I tap the walls, I can tell where the plaster is no longer attached to the limestone. Will the glue and "goo" used for lath and plaster repair adhere to limestone?


    Thank you "This Old House" for finding reproductions of our original metal shingles. I was watching TOH's Florida Keys episode which used these Berridge metal shingles. The raised triangle, metal shingle was patented April 1882, and the cornerstone of our library was laid Thanksgiving day 1884.

  5. #5
    Join Date
    Oct 2013
    Posts
    4

    Default Re: Old Plaster on Stone Repairs

    [IMG][/IMG]

    I am in the process of restoring the plaster in our local museum, an 1884 limestone building. I can tell where the plaster is no longer attached to the stone by tapping on it--it sounds hollow. What do I use to fill the gap behind the plaster? Will the glue and "goo" used for lath and plaster repair adhere to the limestone? Will the "goo" run endlessly behind the plaster? There is also no way to clamp the plaster in place while it dries. Any suggestions?

    By the way, Thank you This Old House for our reproduction shingles! I was watching the Key West TOH project when I immediately exclaimed "there is our shingles!" That got our whole restoration project started. The original metal shingles were patented in April, 1882 and the cornerstone of our library building was laid on Thanksgiving Day 1884. Visually, the Berridge shingles are an exact duplicate. To help pay for the new roof, we had people buy a shingle for $5 and then write a message on the back side.

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