USG IMPERIAL Finish Plasters - Manual (Page 5)

Finish Plaster as a Apply D IAMOND or I MPERIAL Brand Interior Finish Plaster only to interior, structurally sound, clean, smooth monolithic
Base Or Finish Coat Over surfaces that have been treated with a high-quality bonding agent, such as USG ™ Plaster Bonder. Grind ridges and
Monolithic Concrete
high points flush, and brush the concrete surface clean of loose particles. Slight irregularities (less than 1/8 Љ) will
not interfere with smooth application. Treat voids and depressions with bonding agent and fill them with I MPERIAL
Brand Basecoat Plaster, D IAMOND Brand Veneer Basecoat Plaster, or with D IAMOND Brand Interior Finish Plaster job-
aggregated with one-half to one full part sharp, clean, fine silica sand. After application, leave these areas rough
and open, and allow them to set. The pre-fill should not be more than 1/4
Љ thick. If pre-filled areas are allowed to
dry overnight, recoat these areas with USG Plaster Bonder prior to application of the plaster product. If pre-filled
areas are still “green’’ (set, but not dry), there is no need to recoat the surface with the bonding agent.
Job-aggregate the finish coat of finish plaster with one-half to one full part sharp, clean, fine silica sand. Although
this material may be applied unaggregated, the sand promotes good mechanical bond between the finish coat
and the bonder/concrete substrate. The sand-aggregated finish also builds up material over slight irregularities,
producing an acceptable monolithic finished surface without detracting from smooth finishing. In addition, the
aggregated finish provides options for sand float or other sand textured surfaces. Note: Delay smooth troweling
or texturing until finish plaster surface has become firm and stiff enough for texturing.
D IAMOND Brand Finish When applying finish to I MPERIAL Brand Gypsum Base, first apply a fill coat of job-sanded D IAMOND Brand Interior
Plaster to Radiant Heat Finish Plaster (1/2 to 1 parts by weight sand per bag) parallel to the direction of the cable and of sufficient thick
Ceilings, Gypsum Base
ness to completely cover the cable. Do not use the cable as a screed. Level the fill coat with a trowel, rod or darby
Radiant Heat Ceiling
to fill any low spots or to remove any high ridges, etc. “Tooth” fill coat to provide a key for the finish coat by the use
of a serrated darby or by lightly brooming prior to set. The average thickness of the fill coat should be 3/16
Љ.
Do not apply finish coat until after the fill coat has developed sufficient suction. In good drying weather this takes
about two hours after the fill coat has set; in damp and/or cold weather the time interval might extend overnight.
Thus proper heat and ventilation should be provided. Apply job-sanded D
IAMOND Brand Interior Finish Plaster
(1/4 to 1 parts by weight sand) to a finish thickness between 1/16 Љ minimum and 3/32Љ maximum. Scratch in a
tight, thin coat over the entire area, immediately doubling back to the full thickness. Fill all imperfections.
Scratch and double back with the same mix of D IAMOND Brand Interior Finish Plaster. When the surface has become
firm, hold the trowel flat and final trowel using water sparingly. Best results are obtained by continuous application
of an entire ceiling. The total thickness of fill and finish coats should be 1/4
Љ.Always work to a wet edge to avoid
dry joinings.
Radiant Heat Ceilings Use USG ™ Plaster Bonder on concrete in accordance with the manufacturer’s directions, prior to the application
Over Monolithic Concrete of D IAMOND Brand Interior Finish Plaster. The concrete surface must be clean, free of dirt, dust, grease, wax, oil or
other unsound conditions and level.
Coat all metal components in the concrete surface to prevent rusting in the plaster. Remove form ridges. Locate
uneven ceiling areas that may require filling prior to installation of electric cable and plastering. Treat these areas
with USG Plaster Bonder. Then apply D
IAMOND Brand Interior Finish Plaster (fill-coat mix) as a leveling coat and
allow it to set. Caution: Temperature of concrete ceiling with bonding agent and cable must be above 32 °F
before plastering is started. Air temperature must be above 55 °F.
Apply job-sanded D IAMOND Brand Interior Finish Plaster to a thickness of 3/8 Љ in two coats to provide a level sur-
face. First apply a fill coat of finish (sanded 1/2 to 1 parts by weight sand per bag of product) parallel to the direc-
tion of the cable averaging 5/16
Љ thick and of sufficient thickness to cover the cable and anchor device. Do not use
cables as a screed. Level the fill coat with a trowel, rod or darby to fill any low spots or to remove any high ridges,
etc. The surface should be made rough to provide mechanical key or “tooth” for the finish coat by the use of ser-
rated darby or by lightly brooming prior to set.
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