How to Surface a Wavy Plaster Wall

Old plaster walls are notorious for having ridges, dips and waves all over them. While this isn't a structural problem, it can look bad. One way of solving the problem without ripping out those walls and redoing them is to “skim coat” over them with new plaster. The plaster is applied in a thin, flat coat to fill in depressions and dips that give the entire wall a flatter look. You can buy the skim-coat plaster in powdered form and mix it yourself, but pre-mixed plaster is easier.

Dropcloths
10-inch-wide drywall knife
Pre-mixed skim-coat plaster
Sanding pad

Instructions

- 1
  Spread dropcloths along the length of wall. Scrape the drywall knife over the surface, pushing it forward and knocking off any peeling paint or other loose material on the wall.
- 2
  Use the knife to spread plaster over one section of the wall, along the top and at one end, covering about 4 feet on a side. Spread the plaster in a thin coat, with the knife held at a steep angle and the front edge dragged tightly over the surface. Dragging fills the dips and low areas while taking most of the plaster back off the flat areas.
- 3
  Repeat the process for the next section of the wall. Continue section by section, doing the whole wall.
- 4
  Let the plaster dry for six hours. Scrape the surface lightly with your drywall knife, knocking off any bumps or ridges in the new plaster.
- 5
  Repeat the skim-coating process, applying another thin layer of plaster section by section. Let it dry for eight hours. Sand lightly with a sanding pad. The wall is now ready for painting.

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