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Can someone tell me how the finish coat on old three coat plaster work was applied?
After the scratch and base coats on my 100 yr old house, the final finish coat is about 1/8″ thick, white, and glass smooth and with a very hard surface. When it gets wet (from leaks before the roof was fixed), it gets soaked but once it dries out it doesn’t seem damaged in any way. Is this typical of a lime putty finish?
I need to patch large holes (1sq ft and up) and have researched different methods. Seems like the suggested route is to install lathing (exp. metal lath), spray/roll on plaster bond (Larsen plaster weld or USG bonder), then use a three coat system to match up with the old. Does this sound right?
Then that leaves me with the final finish coat. I have bags of Ivory Finish Lime from USG that I was going to aggregate with gypsum plaster for the finish coat – but I would like to match up the finish that was on the existing walls. Is there a way to determine if this was a lime putty finish? Does the finish coat have to be troweled repeatedly to burnish it and compact it after it’s initial application to get it glass smooth and with a very hard surface?
For new walls that are covered with drywall, can I coat them with plaster bonder and install a veneer coat of plaster?
Thanks
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I can answer the last two Q's: yes, yes.
After the final coat, the gauging plaster (gauging here just means "make it flat" -- one such plaster is sold as Champion), begins to set up, which is immediately, you wet the finish coat with a paintbrush immediately followed by a trowel. As the plaster hardens the troweling will take more angle and pressure; the brushed on water softens it momentarily. This is a whole lot easier if you did a good job of truing up the previous scratch or brown coat -- the finish coat can vary in thickness but is intended to be 1/8 or less.
There is a lot of skill involved in troweling the wall, so my walls have a bit more ... character. Which, if consistent, can look nice too. I've occasionally cheated and troweled mud into the tiny flaws to make them go away (don't tell anyone). The added lime, incidentally, is what gives the plaster plasticity. A tip: definitely use a mechanical mixing paddle on a drill or equivalent to blend the plaster & lime putty, and make small batches.
Drywall can be coated with a plaster bonding agent then veneer plastered. Or you can buy blueboard, which is already prepped to accept USG's veneer plaster system. Visit http://www.usg.com, the contractor's section. Blue board may be hard to find with the drywall shortage.
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Can someone tell me how the finish coat on old three coat plaster work was applied?
After the scratch and base coats on my 100 yr old house, the final finish coat is about 1/8" thick, white, and glass smooth and with a very hard surface. When it gets wet (from leaks before the roof was fixed), it gets soaked but once it dries out it doesn't seem damaged in any way. Is this typical of a lime putty finish?
I need to patch large holes (1sq ft and up) and have researched different methods. Seems like the suggested route is to install lathing (exp. metal lath), spray/roll on plaster bond (Larsen plaster weld or USG bonder), then use a three coat system to match up with the old. Does this sound right?
Then that leaves me with the final finish coat. I have bags of Ivory Finish Lime from USG that I was going to aggregate with gypsum plaster for the finish coat - but I would like to match up the finish that was on the existing walls. Is there a way to determine if this was a lime putty finish? Does the finish coat have to be troweled repeatedly to burnish it and compact it after it's initial application to get it glass smooth and with a very hard surface?
For new walls that are covered with drywall, can I coat them with plaster bonder and install a veneer coat of plaster?
Thanks