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1950s to 1960 house with rock lathe (dry wall) covered with a grey brown coat (wire mesh in corners) and then a thin white plaster coat. Was used as a doctors office and we are putting back to the original floorplan (adding a laundry room). Plaster of Paris should work as the top skim coat, but does Any one know the formula of the sandy grey brown coat???

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  • and where to get the glue to apply to new drywall ?
    – Chrisj750
    Commented May 13, 2020 at 13:34
  • I do not understand "glue for drywall" it has always been nailed to the framing.
    – Jack
    Commented May 13, 2020 at 15:15
  • The "glue" is to increase plaster adhesion to the drywall
    – Chrisj750
    Commented May 13, 2020 at 15:20
  • The glue was the stickiness of the mix itself, much like thinset for tile
    – Jack
    Commented May 13, 2020 at 15:24
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    I just use liquid nails or some other construction adhesive, I tend to remove the old lath and plaster and just use Sheetrock usually updating the wiring in each room as I go.
    – Ed Beal
    Commented May 13, 2020 at 18:54

2 Answers 2

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The brown coat s a very weak mix of mortar. Back in the day it may have been a specialized mix for stickiness, so it stuck to the rock lathe. You could use as an alternative a ready mixed mortar for stone veneer. All or at least many repairs I seen in homes with rock lath and plaster, were made by using metal lath, scratch coat, base coat, then white coat.

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  • thanks. Guess I will use the metal lathe and 3 coat method. It is time tested.
    – Chrisj750
    Commented May 13, 2020 at 15:26
  • @Chrisj750 if you'll take the tour, you'll note that the proper way of saying "thanks" is to up vote all answers (sure, there's only one here at the moment) that help you, then click the check-mark next to the one that helped you the most.
    – FreeMan
    Commented Feb 10, 2021 at 13:11
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Plaster from 1945 - 1977, on wire lath? The brown coat was likely a mill mixed product. If the plaster contains vermiculite, it also gypsum, sand, 1-5% asbestos, and most likely doesn't contain any animal hair. ... might want to wear a mask, if disturbing the brown coat.

Are you trying to do a repair? I would use USG StructoLite, for repairing the base and scratch coat. The white coat, Use USG Diamond finish if you have confidence in your troweling skills, and can locate it... Durabond if you can't, or some sort of sand-able setting compound which you could make smooth easily.

Don't use Plaster of Paris, unless your just dealing with holes and not redoing part of a wall.

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