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| We have an 1820's Federalist house currently undergoing a major restoration. The dining room had wallpaper that we removed. Underneath is the original horse hair plaster. It is a little rough and has some cracks and fault lines in it.
When we did some of the other rooms a while ago, we hired someone who used joint compound (aka drywall "mud") on the entire wall. I have also heard recommendations for Redi-Patch. The walls have wainscoating and a plate rail, so the surfaces that will be painted are not more than 4' from top to bottom. What's the best way to prepare this surface for painting so I get a smooth surface? |
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- Posted by sombreuil_mongrel (My Page) on Wed, Mar 3, 10 at 11:07
| We did extensive R&D with horsehair plaster last year; we re-created lime plaster walls in a room of an 1817 house we were restoring, and used it for repairs in other rooms. We were able to buy materials from Virginia Lime Works, and apply three coat work over original hand-split lath. There is a learning curve, but the finished product really has the exact look, and substance of the original process. When you say hairline cracks, I wonder what you mean. It is typical for the white coat to develop spiderweb cracks on the surface that pose no problems or threats; if you mean large settling-type cracks (fissures) that originate at the lath, then those have to be addressed. Drywall materials are not suited for lime plaster repairs, especially not in a historic restoration setting. Beware of using any patching product that contains gypsum for skim-coat repairs, as it is not chemically compatible with lime-based plasters. If your plasterer wants to use them, he's running a risk of premature or rapid failures. The huge downside to lime plaster is the very long cure period, which precludes any paint application for at least 90 days on new walls (which is why gypsum became the standard; speed over quality). Lime plaster has great flexibility which is why it's lasted on the walls as long as is has done. Is your house brick or frame? Casey |
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| The house is brick. The east side of the dining room, however has a wooden bump out with three windows in a sort of "bay window" arrangement. The main ceiling is 9 ft, but the extension is 7'6". The south wall used to be an exterior brick wall, but the porch was enclosed about 100 years ago. The brick is now covered by the wainscoating with plaster above that. When we moved in 11 years ago, we didn't touch the dining room. It was the rental apartment and the wallpaper and wainscoating were in good enough shape. Now that this will become our DR, my wife wants the wallpaper gone. Most of the plaster is in good shape, it's just a little rough for painting. There are two or three significant cracks. The biggest is a triangle about 4" at the base of east wall where the bump out is. As I mentioned above, we had all of the walls skim coated 11 years ago and then we painted them. So far, there are no signs of any cracking or peeling of the paint or plaster. In some cases, with the renovation we moved doorways, so we cut into the skim coated plaster walls. There were no issues with the skim coat separating from the horse hair plaster. Is 11 years not long enough to see the effects of the incompatibility betwen the skim coat and the plaster? Thanks for the help. |
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| The usual problem with applying drywall mud is the use of pre-mixed mud that hardens by drying out. It can actually dry so fast it forms a poor bond. If the mud has stayed put for 11 years the plaster may have been rough enough to establish a good bond. While setting drywall compounds work well for lime-plaster repair, they have even more issues with premature drying. If the moisture is pulled out of them by the plaster they touch quickly they revert back to powder to some degree. Bonding compounds can prevent this, or just misting the plaster with a garden sprayer (or hand sprayer for smaller repairs) until the water barely stays on the surface. At that point wipe away ant visible drops of water and apply the mixed setting compound. Hydrated lime and gauging plaster are the origginal surface, and are still available. The problem is that thelime powder really needs to be mixed and aged for 5-7 days before adding the gauging plaster and additional water to get a workable product. In England they used straight lime putty plaster, but its setting time is months. |
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