International Building Code Section 2512


International Building Code 2512.1

General. Plastering with cement plaster shall not be
less than three coats where applied over metal lath or wire fabric
lath and not less than two coats where applied over masonry,
concrete or gypsum board backing as specified in Section
2510.5. If the plaster surface is to be completely covered by
veneer or other facing material, or is completely concealed by
another wall, plaster application need be only two coats, provided
the total thickness is as set forth in ASTM C 926.

On-grade floor slab. On wood framed or steel
stud construction with an on-grade concrete floor slab system,
exterior plaster shall be applied in such a manner as to
cover, but not to extend below, the lath and paper. The application
of lath, paper and flashing or drip screeds shall comply
with ASTM C 1063.

Weep screeds.Aminimum 0.019-inch (0.48 mm)
(No. 26 galvanized sheet gage), corrosion-resistant weep
screed with a minimum vertical attachment flange of 31/2
inches (89 mm) shall be provided at or belowthe foundation
plate line on exterior studwalls in accordance withASTMC
926. The weep screed shall be placed a minimum of 4 inches
(102 mm) above the earth or 2 inches (51 mm) above paved
areas and be of a type that will allow trapped water to drain
to the exterior of the building. The water-resistive barrier
shall lap the attachment flange. The exterior lath shall cover
and terminate on the attachment flange of the weep screed.

International Building Code 2512.1.1

On-grade floor slab. On wood framed or steel
stud construction with an on-grade concrete floor slab system,
exterior plaster shall be applied in such a manner as to
cover, but not to extend below, the lath and paper. The application
of lath, paper and flashing or drip screeds shall comply
with ASTM C 1063.

International Building Code 2512.1.2

Weep screeds.Aminimum 0.019-inch (0.48 mm)
(No. 26 galvanized sheet gage), corrosion-resistant weep
screed with a minimum vertical attachment flange of 31/2
inches (89 mm) shall be provided at or belowthe foundation
plate line on exterior studwalls in accordance withASTMC
926. The weep screed shall be placed a minimum of 4 inches
(102 mm) above the earth or 2 inches (51 mm) above paved
areas and be of a type that will allow trapped water to drain
to the exterior of the building. The water-resistive barrier
shall lap the attachment flange. The exterior lath shall cover
and terminate on the attachment flange of the weep screed.

International Building Code 2512.2

Plasticity agents. Only approved plasticity agents and
approved amounts thereof shall be added to portland cement.
When plastic cement or masonry cement is used, no additional
lime or plasticizers shall be added. Hydrated lime or the equivalent
amount of lime putty used as a plasticizer is permitted to
be added to cement plaster or cement and lime plaster in an
amount not to exceed that set forth in ASTM C 926.

International Building Code 2512.3

Limitations. Gypsum plaster shall not be used on exterior
surfaces.

International Building Code 2512.4

Cement plaster. Plaster coats shall be protected from
freezing for a period of not less than 24 hours after set has
occurred. Plaster shall be applied when the ambient temperature
is higher than 400F (40C), unless provisions are made to
keep cement plaster work above 400F (40C) during application
and 48 hours thereafter.

International Building Code 2512.5

Second-coat application. The second coat shall be
brought out to proper thickness, rodded and floated sufficiently
rough to provide adequate bond for the finish coat. The second
coat shall have no variation greater than 1/4 inch (6.4 mm) in any
direction under a 5-foot (1524 mm) straight edge.

International Building Code 2512.6

Curing and interval. First and second coats of cement
plaster shall be applied and moist cured as set forth in ASTM C
926 and Table 2512.6.

International Building Code 2512.7

Application to solid backings. Where applied over
gypsum backing as specified in Section 2510.5 or directly to
unit masonry surfaces, the second coat is permitted to be
applied as soon as the first coat has attained sufficient hardness.

International Building Code 2512.8

Alternate method of application. The second coat is
permitted to be applied as soon as the first coat has attained sufficiently
rigidity to receive the second coat.

Admixtures. When using this method of application,
calcium aluminate cement up to 15 percent of the
weight of the portland cement is permitted to be added to the
mix.

Curing. Curing of the first coat is permitted to be
omitted and the second coat shall be cured as set forth in
ASTM C 926 and Table 2512.6.

International Building Code 2512.8.1

Admixtures. When using this method of application,
calcium aluminate cement up to 15 percent of the
weight of the portland cement is permitted to be added to the
mix.

International Building Code 2512.8.2

Curing. Curing of the first coat is permitted to be
omitted and the second coat shall be cured as set forth in
ASTM C 926 and Table 2512.6.

International Building Code 2512.9

Finish coats. Cement plaster finish coats shall be
applied over base coats that have been in place for the time periods
set forth in ASTM C 926. The third or finish coat shall be
applied with sufficient material and pressure to bond and to
cover the brown coat and shall be of sufficient thickness to conceal
the brown coat.