ASTM C842-99

Standard Specification for Application of Interior Gypsum Plaster

SCOPE
1.1 This specification covers the minimum requirements for full-thickness (in accordance with Table 6) interior gypsum plastering on gypsum, metal, masonry, or monolithic concrete bases designed or prepared to receive gypsum plaster.  
Note 1-To secure desirable results, this specification should be coordinated with the provisions of Specification C 841. General information concerning full thickness gypsum plastering is contained in Annex A2, A3, and A4.  
1.2 the values stated in inch-pound units are to be regarded as the standard. The SI (metric) values shown in parentheses are approximate and are provided for information purposes only.  
1.3 The text of this standard references notes and footnotes which provide explanatory material. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of the standard.

General Information

• Status: Historical
• Publication Date: 09-Oct-1999
• ICS: 91.100.10 - Cement. Gypsum. Lime. Mortar
• Technical Committee: C11 - Gypsum and Related Building Materials and Systems
• Drafting Committee: C11.03 - Specifications for the Application of Gypsum and Other Products in Assemblies

Relations

• Replaced By: ASTM C842-05 - Standard Specification for Application of Interior Gypsum Plaster
• Effective Date: 01-May-2005
• Referred By: ASTM C841-23 - Standard Specification for Installation of Interior Lathing and Furring
• Effective Date: 10-Oct-1999
• Referred By: ASTM C28/C28M-10(2020) - Standard Specification for Gypsum Plasters
• Effective Date: 10-Oct-1999
• Referred By: ASTM C206-14(2022) - Standard Specification for Finishing Hydrated Lime
• Effective Date: 10-Oct-1999
• Referred By: ASTM C471M-20ae1 - Standard Test Methods for Chemical Analysis of Gypsum and Gypsum Products (Metric)
• Effective Date: 10-Oct-1999
• Referred By: ASTM C1546-19 - Standard Guide for Installation of Gypsum Products in Concealed Radiant Ceiling Heating Systems
• Effective Date: 10-Oct-1999

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: C 842 – 99
Standard Specification for
Application of Interior Gypsum Plaster
This standard is issued under the fixed designation C 842; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
TABLE 1 Thickness of Plaster
1. Scope *
Thickness of Plaster Including Finish
1.1 This specification covers the minimum requirements for
Plaster Base
Coat, in. (mm)
full-thickness (in accordance with Table 1) interior gypsum
Metal plaster base ⁄8 (16) min
plastering on gypsum, metal, masonry, or monolithic concrete
All other types of plaster base ⁄2 (13) min
bases designed or prepared to receive gypsum plaster.
Unit masonry ⁄8 (16) min
A
Monolithic concrete surfaces:
1.1.1 Gypsum plaster applied to the interior side of exterior
BC 5
Vertical ⁄8 (16) min
walls of masonry or concrete shall be isolated from the exterior
C
1 5
Horizontal ⁄8 (3) to ⁄8 (10)
wall.
A
Base coat plastering of the same proportions as specified for unit masonry is
1.2 Gypsum plasters shall not be used in exterior locations
not prohibited from being used over plain or reinforced monolithic concrete,
or interior “wet” areas. provided the surface is first covered with a metal plaster base or first coated with
a bonding compound.
B
NOTE 1—To secure desirable results, this specification should be Finish coat plaster applied direct to a bonding compound over vertical
monolithic concrete shall be not more than ⁄16 in. (4.8 mm) in thickness. Where
coordinated with the provisions of Specification C 841. General informa-
more than ⁄16 in. of finish coat is required to bring such vertical surface to a true
tion concerning full thickness gypsum plastering is contained in Annex
plane, a base coat of plaster shall first be applied to the bonding compound.
A2, Annex A3, and Annex A4.
C
Where horizontal or vertical monolithic concrete surfaces require more
3 5
than ⁄8 in. (9.5 mm) or ⁄8 in. (15.9 mm) of plaster, respectively, to produce
1.3 Details of construction for a specific assembly to
required lines or surfaces, metal plaster base shall be attached to the concrete
achieve the required fire resistance shall be obtained from
before application of plaster. Where concrete surface requires the application of
more than 1 in. (25.4 mm) of plaster to produce required lines or surfaces, lath
reports of fire-resistance tests, engineering evaluations, or
shall be applied over furring secured to the concrete.
listings from recognized fire testing laboratories.
1.4 Details of construction to achieve required sound con-
trol shall be obtained from reports of tests conducted at
C 35 Specification for Inorganic Aggregates for Use in
recognized sound testing laboratories in accordance with the
Gypsum Plaster
applicable sound tests of Test Methods E 90, C 423, or E 492.
C 59 Specification for Gypsum Casting and Molding Plas-
1.5 The values stated in inch-pound units are to be regarded
ter
as the standard.The SI (metric) values given in parentheses are
C 61 Specification for Gypsum Keene’s Cement
approximate and are provided for information purposes only.
C 206 Specification for Finishing Hydrated Lime
1.6 The text of this standard references notes and footnotes
C 423 Test Method for Sound Absorption and Sound Ab-
which provide explanatory material. These notes and footnotes
sorption Coefficients by the Reverberation Room Method
(excluding those in tables and figures) shall not be considered
C 631 Specification for Bonding Compounds for Interior
as requirements of the standard.
Gypsum Plastering
2. Referenced Documents
C 841 Specification for Installation of Interior Lathing and
Furring
2.1 ASTM Standards:
E 90 Test Method for Laboratory Measurement of
C 5 Specification for Quicklime for Structural Purposes
Airborne-Sound Transmission Loss of Building Partitions
C 11 Terminology Relating to Gypsum and Related Build-
and Elements
ing Materials and Systems
E 492 Test Method for Laboratory Measurement of Impact
C 28 Specification for Gypsum Plasters
Sound Transmission Through Floor-Ceiling Assemblies
Using the Tapping Machine
3. Terminology
This specification is under the jurisdiction of ASTM Committee C-11 on
Gypsum and Related Building Materials and Systems and is the direct responsibility
3.1 Definitions:
of Subcommittee C11.03 on Specifications for Application of Gypsum and Other
Products in Assemblies.
Current edition approved Oct. 10, 1999. Published January 2000. Originally
published as C 842 – 76. Last previous edition C 842 – 98.
2 3
Annual Book of ASTM Standards, Vol 04.01. Annual Book of ASTM Standards, Vol 04.06.
*ASummary of Changes section appears at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C 842
outdoor temperature extremes during construction.
3.1.1 Definitions shall be in accordance with Terminology
C11.
6.2 Ventilation—Sufficient ventilation shall be provided to
3.2 Definitions of Terms Specific to This Standard:
removeexcesswatergivenoffthroughthedryingprocess.(See
3.2.1 catfaces, n—blemishes or rough depressions in the
Appendix X2 for provisions for ventilating underside of roofs
finish coat.
and glazed buildings with and without operable windows.)
3.2.2 coat, n—a thickness or layer of plaster applied over a
surface in a single application. 7. Materials
3.2.2.1 base coat, n—the sum of the scratch and brown
7.1 Gypsum Plasters—Thefollowingplastersshallconform
coats or the total coats in place prior to application of finish
to Specification C 28:
coats.
7.1.1 Ready mixed.
3.2.2.2 brown coat, n—the second coat of plaster applied in
7.1.2 Neat.
three-coat work.
7.1.3 Wood-fibered.
3.2.2.3 finish coat, n—the last coat of plaster applied in
7.1.4 Gauging for finish coat.
either two-coat or three-coat work.
7.2 Gypsum Casting and Molding Plasters—Specification
3.2.2.4 scratch coat, n—the first coat of plaster applied over
C 59.
a lath or other substrate.
7.3 Gypsum Keene’s Cement—Specification C 61.
3.2.2.5 three-coat work, n—plaster applied in three succes-
7.4 Lime:
sive coats, leaving time between coats for setting or drying, or
7.4.1 Finishing Hydrated Lime—Specification C 206, Type
both, of the plaster.
S.
3.2.2.6 two-coat work, n—scratch and brown coats applied
7.4.2 Quicklime for Structural Purposes—Specification
from the same mix with no time allowed for setting of the
C5.
scratch coat before the brown coat is applied.
7.5 Lime Putty—Lime putty exceeding 8 weight % of
3.2.3 gypsum ready mixed plaster, n—calcined gypsum
unhydrated magnesium oxide shall not be used for finish coat
plaster, mixed at the mill with a mineral aggregate, designed to
plaster.
function as a base coat to receive various finish coats.
7.6 Aggregates:
3.2.4 metal bases, n—expanded metal, welded or woven
7.6.1 Aggregates for Base Coat Plaster—Specification
wire, or punched sheet metal plaster bases.
C 35.
3.2.5 smooth-trowel finish, n—a finish resulting from steel
7.6.2 Aggregates for Finish Coat Plasters—Specification
troweling.
C 35, except that gradation shall be within the limits specified
3.2.6 texture finish, n—a finish resulting from (1) trowel
in Table 2.
applicationfollowedbyfloatingortexturingofthesurfacewith
7.6.3 Sand for job mixed lime putty-gypsum gauged, sand
any of a variety of tools using a minimum of water or (2)
float finish (see 9.6.6.1) shall be graded within the limits
machine application which is or is not hand textured.
specified in Table 3.
7.7 Water—Water used in mixing and finishing plaster shall
4. Delivery of Materials
be potable, and free of such amounts of mineral or organic
4.1 All manufactured materials shall be delivered in the
substances that affect the set, the plaster, or any metal in the
original packages, containers, or bundles bearing the brand
system.
name and manufacturer (or supplier) identification.
NOTE 3—Water containing salt or alum, or water in which tools have
been washed, accelerates the “set” and may cause efflorescence. Water
5. Protection of Materials
from stagnant pools and wells frequently contain organic or vegetable
matter which may retard the “set,” cause staining, or interfere with the
5.1 Plasters and other cementitious materials shall be kept
bond.
dry until used; they shall be stored off the ground, under cover,
and away from walls with condensation and other damp
7.8 Bonding Compounds—Specification C 631.
surfaces. Metal products shall be protected, while stored,
8. Surface Preparation
against rusting.
8.1 Substrates—Surfaces of substrates for the application of
6. Environmental Conditions
gypsum plaster shall be free of materials that will inhibit bond
or adhesion, shall be straight, plumb, level, square, and true to
6.1 Temperatures—Where the ambient outdoor temperature
required plan angles and curves. See A2.5.
at the building site is less than 55°F (13°C), a temperature of
not less than 55°F (13°C) and not more than 80°F (27°C) shall
be maintained continuously inside the building for a period of
TABLE 2 Aggregate for Finish Coat Plasters, Percentage
Retained on Each Sieve, Cumulative
not less than one week prior to the application of plaster (Note
2), while the plastering is being applied, and for one week after
Perlite, Natural and Manufactured Sand
Sieve Size Volume,% Weight, %
the plaster has set, or until the plaster has dried. Heat shall be
max min max min
distributed evenly by using deflective or protective screens to
No. 20 (850 µm) 0 . 0 .
prevent concentrated or uneven heat or cold on the plaster. No. 30 (600 µm) 10 . 0.5 .
No. 100 (150 µm) 100 40 100 40
NOTE 2—The requirement should minimize the possibility of plaster
No. 200 (75 µm) 100 70 100 70
cracking due to structural movements caused by thermal changes from
C 842
TABLE 3 Sand for Job-Mixed Lime Putty-Gypsum Gaged Sand
9.4.1 Gypsum Neat Plaster—Proportions of sand, perlite, or
Float Finish, Percent Retained on Each Sieve by Weight,
vermiculite aggregate to 100 lb (45.4 kg) of gypsum neat
Cumulative
plaster shall be not more than those specified in Table 4. (See
Sieve Size max min
A2.3 for equivalent measure for aggregates.)
No. 16 (1.18 mm) 0 0
9.4.2 Gypsum Ready Mixed Plaster—Shall be used with the
No. 30 (600 µm) 50 20
addition of water only.
No. 50 (300 µm) 70 50
No. 100 (150 µm) 100 80 9.4.3 Gypsum Wood-Fibered Plaster—Proportion of damp,
loose sand or perlite or vermiculite shall be not more than 1 ft
(0.028 m ) to 100 lb (45.4 kg) of gypsum wood-fibered plaster.
9.5 Preparation of Lime Putty:
8.1.1 All accessories shall be securely attached to the
9.5.1 Lime putty shall be prepared from Type S hydrated
substrate and be installed to accommodate embedment of
lime or pulverized quicklime, in accordance with the manufac-
flanges.
turer’s printed directions.
8.1.2 Gypsum and Metal Lath—Shall have been installed in
9.5.2 Hydrated Lime—Type S lime shall only be used after
compliance with Specification C 841.
soaking for the time period required in accordance with the
8.2 Conditioning of Surfaces—All depressions in masonry
manufacturer’s printed directions.
and concrete surfaces deeper than ⁄8 in. (3.2 mm) shall be
9.6 Finish Coat Proportions:
brought flush to the surface with compatible materials prior to
9.6.1 Finish coats shall be either ready mixed or job mixed
plaster application. Fins or protrusions extending more
in accordance with Table 5 and Table 6.
than ⁄16 in. (1.6 mm) from the surface shall be removed.
9.6.1.1 Wherethicknessofthefinishcoatismorethan ⁄8 in.
Protrusions less than ⁄16 in. (1.6 mm) shall be feathered out
(3.2 mm), the proportion of the gypsum gauging plaster shall
with compatible materials prior to plaster application.
be increased to minimize shrinkage type cracks.
8.2.1 Masonry—All masonry surfaces shall be wetted im-
9.6.2 Troweled Finishes of lime putty gauged with gypsum
mediately prior to the plaster application. No free water shall
gauging plaster or ready mixed gypsum plaster shall be
remain visible on the substrate surface.
proportioned in accordance with Table 5.
8.2.1.1 Wherethesurfaceistoosmoothtoprovidemechani-
9.6.2.1 Where finish in 9.6.2 is to be applied over base coats
cal key, the surface shall be roughened or bonding compound
containing perlite or vermiculite, the addition of not less
shall be used. (See Annex A2.5 and A2.6.)
3 3 3 3
than ⁄2 ft (0.14 m ) or not more than 1 ft (0.028 m)offine
8.2.1.2 Where bond cannot be obtained over the entire
aggregate meeting the sieve analysis of Table 2 shall be added
surface by the methods specified in 8.2.1.1, self-furring metal
to the mix.
lath shall be used in accordance with Specification C 841.
9.6.3 Troweled finishes of lime putty gauged with gypsum
8.2.2 Monolithic concrete—bonding compounds shall be
Keene’s cement shall be specified as medium or hard and shall
used prior to plastering all monolithic concrete surfaces. (See
be proportioned in accordance with Table 5.
A2.6.)
9.6.3.1 When finish in 9.6.3 is mechanically mixed, the
8.2.3 Grounds, beads, and screeds shall be installed prior to
water shall be placed in the mixer first, then the lime, the fine
the plastering as modified herein.
aggregate (if used), and finally the gypsum Keene’s cement.
8.3 Grouting:
9.6.4 Troweledfinishesofgypsumreadymixedplastershall
8.3.1 Metal bases for solid partitions shall be grouted with
be mixed in accordance with Table 5.
gypsum plaster leaving ⁄4 in. (6.4 mm) below the top edge of
9.6.5 Float finishes of lime putty gauged with gypsum
the base, and be formed with a center groove so that the lath
extends ⁄4 in. (19 mm) below the top edge of the base, or gauging plaster shall be proportioned in accordance with Table
5.
plaster grout shall be placed after installation of lath.
8.3.2 Metal Frames—Hollow door and window frames 9.6.5.1 When finish in 9.6.6 is to be mixed with sand, the
shall be filled with gypsum plaster grout. sand shall be graded within the limits shown for basecoats in
Specification C 35 except that all of the sand shall pass a No.
9. Mix Design
8 (2.36 mm) sieve.
9.6.6 Float finishes of lime putty gauged with gypsum
9.1 Mixing, General—All plaster mixing shall be done by
Keene’scementshallbeproportionedinaccordancewithTable
mechanical means unless hand mixing is specified.
5.
9.1.1 Retempered, partially set, frozen, caked or lumpy
9.6.6.1 When the finish in 9.6.6 is to be mechanically mixed
material shall not be used.
wet, follow procedures in 9.6.3.1. For mixing dry, add lime
9.1.2 Each batch shall be mixed separately and mixers shall
first, then gypsum K
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