Table 7-1.Base Coat Proportions for Different Types of Work
of lime putty, or 94 pounds (one sack) of portland
FINISH COAT PROPORTIONS. A lime finish
cement. One part of aggregate means 100 pounds of
sand or 1 cubic foot of vermiculite or perlite. Note:
Vermiculite and perlite are not used with lime plaster.
While aggregate parts given for gypsum or portland
cement plaster may be presumed to refer to either sand
or vermiculite/perlite, the aggregate part given for lime
plaster means sand only.
BASE COAT PROPORTIONS. Two-coat
plasterwork consists of a single base coat and a finish
coat. Three-coat plasterwork consists of two base coats
(the scratch coat and the brown coat) and a finish coat.
Portland cement plaster cannot be applied to a
gypsum base. Lime plaster can, but, in practice, only
gypsum plaster is applied to gypsum lath as a base coat.
For two-coat work on gypsum lath, the recommended
base coat proportions for gypsum plaster are 1:2.5. For
two-coat work on a masonry (either monolithic concrete
or masonry) base, the recommended base coat
proportions are shown in table 7-1. Also shown in table
7-1 are proportions for three-coat work on a masonry
base and proportions for work on metal lath.
For three-coat work on gypsum lath, the recom-
mended base coat proportions for gypsum plaster are
shown in table 7-2.
can be applied over a lime, gypsum, or portland cement
base coat. Other finishes should be applied only to base
coats containing the same cementitious material. A
gypsum-vermiculite finish should be applied only to a
gypsum-vermiculite base coat.
Finish coat proportions vary according to whether
the surface is to be finished with a trowel or with a float.
(These tools are described later.) The trowel attains a
smooth finish; the float produces a textured finish.
For a trowel-finish coat using gypsum plaster, the
recommended proportions are 200 pounds of hydrated
lime or 5 cubic feet of lime putty to 100 pounds of
gypsum gauging plaster.
Table 7-2.Recommended Base Coat Proportions for Gypsum