Figure 7-9.-Control joint.finish. They are removed after the plaster has dried.Narrow strip grounds (fig. 7-10, view B) can also beused around interior openings.In window and exterior door openings, the framesare normally in place before the plaster is applied. Thus,the inside edges of the side and head jamb can, and oftendo, serve as grounds. The edge of the window might alsobe used as a ground, or you can use a narrow7/8-inch-thick ground strip nailed to the edge of the 2-by 4-inch sill (fig. 7-10, view C). These are normallyleft in place and covered by the casing.A similar narrow ground or screed is used at thebottom of the wall to control the thickness of the gypsumplaster and to provide an even surface for the baseboardand molding. This screed is also left in place after theplaster has been applied.MixingSome plaster comes ready-mixed, requiring onlythe addition of enough water to attain minimum requiredFigure 7-10.—Plaster grounds.workability. For job mixing, tables are available givingrecommended ingredient proportions for gypsum, lime,lime-portland cement, and portland cement plaster forbase coats on lath or on various types of concrete ormasonry surfaces, and for finish coats of various types.In this chapter, we’ll cover recommended proportionsfor only the more common types of plastering situations.In the following discussion, one part of cement-itious material means 100 pounds (one sack) of gypsum,100 pounds (two sacks) of hydrated lime, 1 cubic foot7-9
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business