Composition
Plaster is a cement-like material that primarily contains gypsum (CaSO4 2H²O) or lime.
It may also
contain aggregate or fibers (horse hair or fiberglass) to stabilize and strengthen the
compound. "Gypsum was introduced in the United States in 1785 by
Benjamin Franklin. He had encountered the material known as 'Plaster of Paris' in France, where it was used as a wall finish,
casting material and soil nutrient."(1)
Drywall is essentially pre-manufactured boards of compressed plaster
with a paper skin.
When plaster is applied to a (wood, rock
or metal) lath substrate on walls and ceilings, it is
applied in two or
three coats. The first or scratch coat is a sand, cement and gypsum or
lime mix.
The second coat of the same material is then applied after the first
coat has dried. The final coat is a white coat that contains
white plaster and a high lime content that forms a smooth, hard surface.
Plaster-Drywall Hybrid – 1/2-inch gypsum blue-board with a hard skim
coat of plaster provides a gypsum board base and the rock hard finish of
real plaster. This material is used in some custom construction when a buyer
does not want drywall. At approximately $1.75 per SF, its cost is roughly
50% more than finished drywall and approximately 40% less than three-coat
plaster.
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Interior Main Page
Ceiling and Wall Main Page
Drywall Wood Lath
Rock Lath
Wire (Metal) Lath
Other
Finish Material Other
Ceiling Types
Interior Trim
