ASTM C844-15(2021)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation:C844 −15 (Reapproved 2021)
Standard Specification for
Application of Gypsum Base to Receive
Gypsum Veneer Plaster
This standard is issued under the fixed designation C844; 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 (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope 1.9 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.1 Thisspecificationcoverstheminimumrequirementsfor,
ization established in the Decision on Principles for the
andmethodsof,applicationofgypsumveneerbaseforgypsum
Development of International Standards, Guides and Recom-
veneer plasters.
mendations issued by the World Trade Organization Technical
1.2 Gypsum veneer base shall not be used as a base for
Barriers to Trade (TBT) Committee.
direct adhesive application of ceramic, metal, or plastic tile in
2. Referenced Documents
areas exposed to abnormal moisture or humidity or tempera-
ture. 2
2.1 ASTM Standards:
C11 Terminology Relating to Gypsum and Related Building
1.3 Details of construction for a specific assembly to
achieve the required fire resistance shall be obtained from Materials and Systems
C423 Test Method for SoundAbsorption and SoundAbsorp-
reports of fire-resistance tests, engineering evaluations, or
listings from recognized fire testing laboratories. tion Coefficients by the Reverberation Room Method
C514 Specification for Nails for the Application of Gypsum
1.4 Where a specific degree of sound control is required for
Board
veneer plaster assemblies and constructions, details of con-
C587 Specification for Gypsum Veneer Plaster
struction shall be in accordance with official reports of tests
C754 Specification for Installation of Steel Framing Mem-
conducted in recognized sound testing laboratories in accor-
bers to Receive Screw-Attached Gypsum Panel Products
dance with the applicable sound tests, Test Methods C423,
C954 SpecificationforSteelDrillScrewsfortheApplication
E90,or E492.
of Gypsum Panel Products or Metal Plaster Bases to Steel
1.5 Where this specification is more stringent (size or
Studs from 0.033 in. (0.84 mm) to 0.112 in. (2.84 mm) in
thickness of framing; spacing of fasteners) than the fire-rated
Thickness
construction, this specification shall govern; otherwise, the
C955 Specification for Cold-Formed Steel Structural Fram-
construction described in the fire test report shall govern.
ing Members
C1002 Specification for Steel Self-Piercing Tapping Screws
1.6 Unheated spaces above gypsum veneer base ceilings
for Application of Gypsum Panel Products or Metal
shall be properly ventilated (see Appendix X3).
Plaster Bases to Wood Studs or Steel Studs
1.7 The values stated in inch-pound units are to be regarded
C1007 Specification for Installation of Load Bearing (Trans-
as the standard.The SI (metric) values given in parentheses are
verse and Axial) Steel Studs and Related Accessories
approximate and are provided for information purposes only.
C1047 Specification for Accessories for Gypsum Wallboard
1.8 The text of this standard references notes and footnotes
and Gypsum Veneer Base
which provide explanatory material. These notes and footnotes
C1396/C1396M Specification for Gypsum Board
(excluding those in tables and figures) shall not be considered
C1546 Guide for Installation of Gypsum Products in Con-
as requirements of the standard.
cealed Radiant Ceiling Heating Systems
E90 Test Method for Laboratory Measurement of Airborne
Sound Transmission Loss of Building Partitions and
This specification is under the jurisdiction of ASTM Committee C11 on
Elements
Gypsum and Related Building Materials and Systems and is the direct responsibility
ofSubcommitteeC11.03onSpecificationsfortheApplicationofGypsumandOther
Products in Assemblies. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
CurrenteditionapprovedJune1,2021.PublishedJuly2021.Originallyapproved contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
in 1978. Last previous edition approved in 2015 as C844 – 15. DOI: 10.1520/ Standards volume information, refer to the standard’s Document Summary page on
C0844-15R21. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C844−15 (2021)
E492 Test Method for Laboratory Measurement of Impact minimum outside measure and divergent points. Staples shall
Sound Transmission Through Floor-Ceiling Assemblies be used only for the base ply of two-ply application over wood
Using the Tapping Machine framing.
2.2 American Softwood Lumber Standard:
4.10 Steel Framing, Non-load Bearing—Specification C645
PS 20 American Softwood Lumber Standard
for the specified design criteria.
4.11 Accessories—Specification C1047.
3. Terminology
4.12 Adhesive—For application of gypsum base to steel
3.1 Definitions:
framing, the adhesive shall be as recommended by the manu-
3.1.1 Definitions shall be in accordance with Terminology
facturer of the gypsum base.
C11.
3.2 Definitions of Terms Specific to This Standard:
4.13 Steel Framing Load Bearing—Specification C955.
3.2.1 base ply, n—first ply of gypsum base in multiple ply
4.14 Wood Framing—American Lumber Softwood Stan-
application.
dard PS–20.
3.2.2 face ply, n—outer or visible layer of gypsum base in
multiple ply application. 5. Delivery of Materials
3.2.3 fastener, n—nails, screws, or staples used for the
5.1 All materials shall be delivered in the original packages,
application of the gypsum base or backing board.
containers, or bundles bearing the brand name and manufac-
turer (or supplier) identification.
3.2.4 framing member, n—that portion of the framing,
furring, blocking, and so forth, to which the gypsum base is
6. Shipping, Handling and Storage
attached. Unless otherwise specified, the surface to which
6.1 Gypsum board shall be shipped so as to be kept dry.
abuttingedgesorendsareattachedshallbenotlessthan1 ⁄2 in.
(38 mm) wide for wood members, not less than 1 ⁄4 in.
6.2 Gypsum board shall be stored so as to be kept dry,
(32 mm) wide for steel members, and not less than 6 in.
preferably inside a building, under a roof. Gypsum board shall
(152 mm) wide for gypsum studs. For internal corners or
be neatly stacked flat with care taken to prevent sagging or
angles, the bearing surface shall be not less than ⁄4 in.
damage to edges, ends, and surfaces.
(19 mm).
6.3 Where necessary to store gypsum board outside, it shall
3.2.5 parallel application, n—gypsum base application
be stacked flat, off the ground, supported on a level platform,
where the gypsum base edge is applied parallel to the framing
and fully protected from weather and direct sunlight exposure.
members.
6.4 Prior to application, the building exterior shall be so
3.2.6 perpendicular application, n—gypsum base applica-
enclosed to protect the gypsum base from exposure to weather
tion where the gypsum base edge is applied at right angles to
and direct sunlight.
the framing members.
NOTE 1—The bond of alkaline veneer plaster to gypsum base will be
impaired if the base is exposed to direct light or sunlight for extended
4. Materials
periods.
4.1 Materials shall conform to the respective specifications
and standards and to the requirements specified herein. 7. Environmental Conditions
4.2 Gypsum Base for Veneer Plasters (hereinafter referred
7.1 Application of Gypsum Base and Adhesives—A room
to as “gypsum base”)—Specification C1396/C1396M. temperature of not less than 40 °F (4 °C) shall be maintained
during application of gypsum base except when adhesive is
4.3 Gypsum Backing Board—Specification C1396/
used for the attachment of gypsum base. For the bonding of
C1396M.
adhesive, a room temperature of not less than 50 °F (10 °C)
4.4 Special Fire-Retardant Gypsum Base—Specification
shall be maintained for 48 h prior to application and continu-
C1396/C1396M, Type X.
ously thereafter until adhesive is completely dry. When a
4.5 Foil-Backed Gypsum Base—Specification C1396/ temporary heat source is used, the temperature shall not exceed
C1396M. 95 °F (35 °C) in any room or area. Adequate ventilation shall
be maintained in the working area during the application and
4.6 Gypsum Veneer Plaster—Specification C587.
adhesive curing process.
4.7 Nails—Specification C514.
8. Application of Gypsum Base
4.8 Screws:
4.8.1 Non-load Bearing Steel—Specification C1002. 8.1 General Requirements:
4.8.2 Load Bearing Steel—Specification C954.
8.1.1 Installation of steel framing shall be in accordance
with applicable Specifications C754 or C1007 except where
4.9 Staples—No. 16 USS gauge 0.063-in. (1.6 mm) flat-
7 superseded by requirements of Table 1.
tened galvanized wire with ⁄16-in. (11.1 mm) wide-crown
NOTE 2—For general wood framing requirements, see Appendix X2.
8.1.2 Method of Cutting—The gypsum base shall be cut by
Available from National Institute of Standards and Technology (NIST), 100
Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070, http://www.nist.gov. scoring and breaking or by sawing, working from the face side.
C844−15 (2021)
TABLE 1 Maximum Framing Spacing
Maximum On Center
Single-ply Base
Application to Framing Spacing of Framing, in.
(Thickness), in. (mm)
(mm)
Ceilings:
⁄2 (12.7) parallel 16 (406)
A
⁄2 (12.7) perpendicular 24 (610)
B
⁄8 (15.9) perpendicular 24 (610)
Sidewalls:
C
⁄8 (9.5) perpendicular 16 (406)
⁄2 (12.7) parallel 16 (406)
A
⁄2 (12.7) perpendicular 24 (610)
B
⁄8 (15.9) parallel or perpendicular 24 (610)
A
⁄2-in. (12.7 mm) gypsum base applied perpendicular on 24-in. (610 mm) on
centers framing shall be considered to be minimum construction.
B
For ⁄8-in. (15.9 mm) base, perpendicular on ceilings and either perpendicular or
parallel on sidewalls at 24-in. (610 mm) on centers spacing, only two-component
veneer plaster or special joint reinforcement, as recommended by the gypsum
veneer plaster manufacturer, shall be used.
C
⁄8-in. (9.5 mm) gypsum base shall be used over wood framing with two-
component veneer plaster systems only.
When cutting by scoring, the face shall be cut with a knife or 8.2.7 Penetration of mechanical fasteners into supporting
other suitable tool and the gypsum base snapped back away framing members shall be not less than:
from the cut face. The back shall be broken by snapping the
Nails Screws Staples
7 5 5
gypsum base in the reverse direction, or by cutting with a knife Wood: ⁄8 in. (22 mm) ⁄8 in. (15 mm) ⁄8 in. (15 mm), each leg
Steel: . ⁄8 in. (9 mm) .
or other suitable tool.
8.1.3 All cut edges and ends of the gypsum base shall be 8.3 Control Joints:
smoothed to obtain neat jointing. Cut-outs for pipes, fixtures,
8.3.1 Control joints shall be installed in ceilings more than
2 2
or other small openings on the face and back of the base shall
2500 ft (232 m ) in area that are constructed with perimeter
be scribed in outline before removing or cut out with a saw or
relief. The distance between control joints shall be not more
other suitable tool. The gypsum base shall be scribed where it
than 50 ft (15 m) in either direction.
2 2
meets projecting surfaces. Base shall be brought lightly into
8.3.2 Ceilings of more than 900 ft (85 m ) in area con-
contact with adjacent panels but not forced into place.Abutting
structed without perimeter relief shall have control joints
ends and edges shall fit neatly.
installed with spacing not to exceed 30 ft (9 m) in either
8.1.4 When gypsum base is to be applied to both ceiling and
direction.
walls, the base shall be applied to the ceiling and then to the
8.3.3 Control joints shall be installed where ceiling framing
walls.
or furring changes direction or where construction joints occur
in the base building construction. In partitions, walls, or wall
8.2 Fastening, Mechanical:
furring, the distance between control joints shall be not more
8.2.1 The gypsum base shall be held in firm contact with the
than 30 ft (9 m).
underlying support while driving any fastener.
8.2.2 Fastener application shall proceed from the center of 8.3.4 A ceiling height door frame, installed in accordance
the field of the gypsum base to the ends and edges or shall with the spacing requirements set forth in 8.3, functions as a
begin along one edge and proceed toward the other edge. control joint.
8.2.3 Except where required for fire rating, structural
performance, or other special considerations, fastening to top
9. Application of Single-ply Gypsum Base
or bottom plates shall not be required.
9.1 The maximum spacing of framing members for single-
8.2.4 Fasteners shall be spaced not less than ⁄8 in. (9.5 mm)
ply gypsum base construction shall be not more than those
from the edges and ends of the gypsum base. Fasteners used at
shown in Table 1.
edges or at base ends in horizontal application shall not be
more than 1 in. from edges or ends. 9.2 In single-ply installation, all ends and edges of gypsum
8.2.5 Nails and screws shall be driven to a point flush with base shall occur over framing members or other solid backing
the gypsum base surface without breaking the surface paper or except where treated joints occur at right angles to framing or
furring members.
damaging the surrounding gypsum core and without stripping
the framing member around the screws.
9.3 Joints on opposite sides of a partition shall be arranged
8.2.6 Staples shall be driven so that both legs penetrate the
to occur on different framing members.
support member and the crown bears tightly against the
9.4 Fasteners (Single-ply Application):
backing board, but does not cut into the face paper. The staple
shall be driven with the crown parallel to framing members. 9.4.1 Nail Spacing—Space nails a maximum of 7 in.
Staples shall be used only for the first ply in two-ply gypsum (178 mm) on centers on the ceiling and a maximum of 8 in.
base systems. (203 mm) on centers on the walls.
C844−15 (2021)
9.4.2 Double Nailing—Nails shall be spaced as shown in double nailing (Fig. 1) or screw application (see Figs. 3 and 4).
Fig. 1 and applied as follows: At sidewall vertical angles (Fig. 5), the overlapping base shall
9.4.2.1 Starting at the center of the base, nails shown as be applied so as to bring the back of the underlying board into
solid dots shall be applied by row starting with row 1, then firm contact with the face of the framing member behind it.
rows 2 and 2A, 3 and 3A, 4 and 4A. Base shall be kept tight
10. Adhesive-Mechanical Fastener Application
against the framing throughout the procedure.
10.1 Except as modified herein, application shall be in
9.4.2.2 Using the procedure in 9.4.2.1, second nails shown
accordance with Section 9.
by circles shall be applied.
9.4.2.3 As an alternative procedure, second nails shall be
10.2 Surfaces of gypsum base and framing to receive
permitted to be applied immediately after all first nails in each
adhesive shall be free of any foreign matter that impairs the
individual row have been driven in accordance with 9.4.2.1.
bond.
9.4.2.4 Single nails shall be used on the perimeter of the
10.3 Abead of adhesive ⁄8 in. (9.5 mm) in diameter shall be
base.
appliedtothefaceofallwoodframingmembers,exceptplates,
NOTE3—Itmaybenecessarytoresetthefirstnailsineachrowafterthe
thatsupportthegypsumbase.Aspressureisappliedtothebase
second nails have been set.
theadhesiveshallspreadtoanaveragewidthof ⁄4 in.(19mm)
9.4.3 Nails for single-ply application over wood members
approximately ⁄8 in. (3.2 mm) thick.Application patterns shall
shall be as follows: be shown as in Fig. 6.
Gypsum Base Thickness, 10.3.1 Where two adjacent pieces of gypsum base abut
Nails, in. (mm)
in. (mm)
(ends or edges) on a framing member, two parallel beads of
3 1
⁄8 (9.5) 1 ⁄4 (32)
adhesive shall be applied to the framing member. Application
1 3
⁄2 (12.7) 1 ⁄8 (35)
5 1
patterns shall be as shown in Fig. 6.
⁄8 (15.9) 1 ⁄2 (38)
9.4.4 Where a specific degree of fire resistance is required
10.4 Adhesive shall be applied to an area no greater than
for gypsum board assemblies and constructions, nails of same
will be covered with gypsum base within the “open time” of
or larger length, shank diameter, and head bearing area, as
the adhesive.
those described in the applicable fire test report shall be used.
10.5 Fastener Spacing:
9.4.5 Screw Spacing—Screws shall be spaced not more than
10.5.1 Where the properties of the adhesive ensure bridging
12 in. (305 mm) on center along framing members for wall or
between the gypsum base and the wood framing, no fastening
ceiling application.
shallberequiredinthefieldofthebaseforwalls.Insuchcases,
9.5 Floating Interior Angles—The floating angle method of
perimeter fastening, 16 in. (406 mm) on center, shall be
application is applicable where single nailing, double nailing,
required.
or screw attachment is used, and helps to minimize the
10.5.2 Where the properties of the adhesive achieve no
possibility of cracking in areas adjacent to a wall and ceiling
positive bridging between the board and the wood framing,
intersection. When using this method the base shall be applied
eit
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