ASTM C635/C635M-22

Standard Specification for Manufacture, Performance, and Testing of Metal Suspension Systems for Acoustical Tile and Lay-in Panel Ceilings

ABSTRACT
This specification covers metal ceiling suspension systems used primarily to support acoustical tile or acoustical lay-in panels. Some suspension systems incorporate locking assembly details that enhance performance by providing some continuity or load transfer capability between adjacent sections of the ceiling grid. The structural classification or grade of ceiling suspension systems shall be determined by the capability of main runners or nailing bars to support a uniformly distributed load. These classifications shall be: light-duty systems; intermediate-duty systems; and heavy-duty systems. The structural classification of ceiling suspension systems shall be based on the load-carrying capacity of the main runners of the structural network. Suspension system structural members shall conform to the following tolerance requirements: metal thickness; straightness; length; overall cross-section dimensions; and section squareness.
SCOPE
1.1 This specification covers metal ceiling suspension systems used primarily to support acoustical tile or acoustical lay-in panels.  
1.2 Some suspension systems incorporate locking assembly details that enhance performance by providing some continuity or load transfer capability between adjacent sections of the ceiling grid. The test methods of Test Methods E3090/E3090M referenced in this specification do not provide the means for making a complete evaluation of continuous beam systems, nor for assessing the continuity contribution to overall system performance. However, the test methods can be used for evaluating primary structural members in conjunction with secondary members that interlock, as well as with those of noninterlocking type.  
1.3 While this specification is applicable to the exterior installation of metal suspension systems, the atmospheric conditions and wind loading require additional design attention to ensure safe implementation. For that reason, a specific review and approval should be solicited from the responsible architect and engineer, or both, for any exterior application of metal suspension systems in the construction of a new building or building modification.  
1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.  
1.5 The following safety hazards caveat pertains only to the test methods described in this specification. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.6 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.

General Information

• Status: Published
• Publication Date: 14-May-2022
• ICS: 91.120.20 - Acoustics in building. Sound insulation
• Technical Committee: E33 - Building and Environmental Acoustics
• Drafting Committee: E33.04 - Application of Acoustical Materials and Systems

Relations

• Refers: ASTM E3090/E3090M-19 - Standard Test Methods for Strength Properties of Metal Ceiling Suspension Systems
• Effective Date: 01-Oct-2019
• Refers: ASTM E3090/E3090M-18 - Standard Test Methods for Strength Properties of Metal Ceiling Suspension Systems
• Effective Date: 01-Nov-2018
• Refers: ASTM E3090/E3090M-17 - Standard Test Methods for Strength Properties of Metal Ceiling Suspension Systems
• Effective Date: 01-Apr-2017
• Refers: ASTM C634-13 - Standard Terminology Relating to Building and Environmental Acoustics
• Effective Date: 01-Sep-2013
• Refers: ASTM C634-11 - Standard Terminology Relating to Building and Environmental Acoustics
• Effective Date: 01-Dec-2011
• Refers: ASTM B117-11 - Standard Practice for Operating Salt Spray (Fog) Apparatus
• Effective Date: 01-Oct-2011
• Refers: ASTM C634-10a - Standard Terminology Relating to Building and Environmental Acoustics
• Effective Date: 01-Sep-2010
• Refers: ASTM C634-10 - Standard Terminology Relating to Building and Environmental Acoustics
• Effective Date: 01-Jun-2010
• Refers: ASTM B117-09 - Standard Practice for Operating Salt Spray (Fog) Apparatus
• Effective Date: 01-Jul-2009
• Refers: ASTM C634-09 - Standard Terminology Relating to Building and Environmental Acoustics
• Effective Date: 01-Apr-2009
• Refers: ASTM D1735-08 - Standard Practice for Testing Water Resistance of Coatings Using Water Fog Apparatus
• Effective Date: 01-Nov-2008
• Refers: ASTM C634-08a - Standard Terminology Relating to Building and Environmental Acoustics
• Effective Date: 01-Sep-2008
• Refers: ASTM C634-08 - Standard Terminology Relating to Building and Environmental Acoustics
• Effective Date: 15-Mar-2008
• Refers: ASTM B117-07a - Standard Practice for Operating Salt Spray (Fog) Apparatus
• Effective Date: 15-Dec-2007
• Refers: ASTM B117-07 - Standard Practice for Operating Salt Spray (Fog) Apparatus
• Effective Date: 01-Mar-2007

Overview

ASTM C635/C635M-22, published by ASTM International, is the standard specification for the manufacture, performance, and testing of metal suspension systems used to support acoustical tile and lay-in panel ceilings. These metal ceiling suspension systems are designed for both interior and exterior ceiling applications where reliable support, durability, and consistent appearance are critical. The standard addresses ceiling suspension systems’ key structural and dimensional characteristics, helping ensure uniform quality and compatibility across residential, commercial, and industrial building projects.

Key Topics

• Structural Classification:
  Ceiling suspension systems are classified by their load-carrying capacity based on the main runners or nailing bars’ ability to support a uniformly distributed load. The standard designates three classifications:
  • Light-duty systems: Suitable for minimal ceiling loads, typical in residential and light commercial settings.
  • Intermediate-duty systems: Designed for moderate additional loads such as light fixtures and air diffusers, found in standard commercial environments.
  • Heavy-duty systems: Intended for heavier ceiling loads in commercial spaces with significant fixtures or equipment.
• Component Tolerances:
  The specification sets out requirements for the allowable tolerances in:
  • Metal thickness
  • Straightness, bow, camber, and twist
  • Length and slot spacing
  • Overall cross-section dimensions and section squareness These tolerances ensure ceiling grid systems fit and assemble correctly, maintaining structural integrity and visual alignment.
• Coatings and Finishes:
  The standard details requirements for protective coatings on metal suspension system components, such as galvanized or anodized finishes. For exposed components, decorative finishes are required, and options for color and texture must meet project needs and maintain durability.
• Environmental and Safety Considerations:
  For exterior applications, special attention must be given to atmospheric conditions and wind loading. The standard requires that any exterior installation be reviewed and approved by architects or engineers. Proper safety, health, and environmental practices must be observed when using and testing according to this standard.
• Performance Testing:
  Suspension systems must be tested according to referenced ASTM methods, such as ASTM E3090/E3090M for load performance and deflection limits. Special tests for severe environments, such as salt spray (ASTM B117) and high humidity (ASTM D1735), are also referenced for systems exposed to harsh conditions.

Applications

• Commercial Buildings:
  Most commonly used in office buildings, retail spaces, schools, and healthcare facilities where acoustical tile and lay-in ceilings are standard.
• Residential Projects:
  Applied in basements, home offices, and other living spaces for both aesthetic ceiling finishes and improved acoustics.
• Industrial and Institutional Settings:
  Used in spaces that require robust support for larger fixtures or where frequent reconfiguration of ceilings is necessary.
• Exterior Installations:
  When applied outdoors, additional engineering review is mandated to address environmental factors such as moisture, humidity, and wind loads.
• Retrofit and Renovation:
  Suitable for upgrading existing ceiling grids to comply with modern performance, safety, and environmental standards.

Related Standards

• ASTM C634: Terminology Relating to Building and Environmental Acoustics
• ASTM E3090/E3090M: Test Methods for Strength Properties of Metal Ceiling Suspension Systems
• ASTM B117: Practice for Operating Salt Spray (Fog) Apparatus
• ASTM D1735: Practice for Testing Water Resistance of Coatings Using Water Fog Apparatus

ASTM C635/C635M-22 is essential for architects, engineers, contractors, and suppliers involved in the specification, installation, and inspection of acoustical ceiling systems. Compliance ensures safety, structural reliability, and performance in a wide range of building environments. For further detail or to confirm specific requirements, always consult the official ASTM publication.

Standards Content (Sample)

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:C635/C635M −22
Standard Specification for
Manufacture, Performance, and Testing of Metal Suspension
Systems for Acoustical Tile and Lay-in Panel Ceilings
This standard is issued under the fixed designation C635/C635M; the number immediately following the designation indicates the year
of original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.
A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope mental practices and determine the applicability of regulatory
limitations prior to use.
1.1 This specification covers metal ceiling suspension sys-
1.6 This international standard was developed in accor-
tems used primarily to support acoustical tile or acoustical
dance with internationally recognized principles on standard-
lay-in panels.
ization established in the Decision on Principles for the
1.2 Some suspension systems incorporate locking assembly
Development of International Standards, Guides and Recom-
detailsthatenhanceperformancebyprovidingsomecontinuity
mendations issued by the World Trade Organization Technical
or load transfer capability between adjacent sections of the
Barriers to Trade (TBT) Committee.
ceilinggrid.ThetestmethodsofTestMethodsE3090/E3090M
2. Referenced Documents
referenced in this specification do not provide the means for
makingacompleteevaluationofcontinuousbeamsystems,nor
2.1 ASTM Standards:
for assessing the continuity contribution to overall system
B117 Practice for Operating Salt Spray (Fog) Apparatus
performance. However, the test methods can be used for
C634 Terminology Relating to Building and Environmental
evaluating primary structural members in conjunction with
Acoustics
secondary members that interlock, as well as with those of
D1735 Practice for Testing Water Resistance of Coatings
noninterlocking type.
Using Water Fog Apparatus
E3090/E3090M Test Methods for Strength Properties of
1.3 While this specification is applicable to the exterior
Metal Ceiling Suspension Systems
installation of metal suspension systems, the atmospheric
conditionsandwindloadingrequireadditionaldesignattention
3. Terminology
to ensure safe implementation. For that reason, a specific
3.1 Terms used in this standard are defined either in Termi-
review and approval should be solicited from the responsible
nology C634 or within this standard. The definition of terms
architect and engineer, or both, for any exterior application of
explicitly given within this standard take precedence over
metalsuspensionsystemsintheconstructionofanewbuilding
definitions given in Terminology C634. The definitions within
or building modification.
Terminology C634 and this standard take precedence over any
1.4 The values stated in either SI units or inch-pound units
other definitions of defined terms found in any other
are to be regarded separately as standard. The values stated in
documents, including other documents that may be referenced
each system may not be exact equivalents; therefore, each
in this standard.
system shall be used independently of the other. Combining
3.2 Definitions of Terms Specific to This Standard:
values from the two systems may result in non-conformance
3.2.1 backing board, n—a flat sheet of gypsum board to
with the standard.
which acoustical tile is attached using adhesive, screws,
1.5 The following safety hazards caveat pertains only to the
staples, or other suitable means (Fig. 1c).
test methods described in this specification. This standard does
3.2.2 bow, n—the maximum component of deviation in the
not purport to address all of the safety concerns, if any,
vertical plane of a main runner, cross runner, or wall molding
associated with its use. It is the responsibility of the user of this
where the centroidal axis of these structural components has
standard to establish appropriate safety, health, and environ-
been permanently deformed from end to end into the shape of
a simple regular curve during the manufacturing process (Fig.
2).
This specification is under the jurisdiction of ASTM Committee E33 on
Building and Environmental Acoustics and is the direct responsibility of Subcom-
mittee E33.04 on Application of Acoustical Materials and Systems. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved May 15, 2022. Published June 2022. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1969. Last previous edition approved in 2017 as C635/C635M – 17. Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/C0635_C0635M-22. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C635/C635M−22
FIG. 1Three Types of Ceiling Suspension Systems Showing All Components
3.2.2.1 Discussion—The meanings for bow and camber 3.2.4 carrying channel, n—metal section that supports the
given here may differ from those applied elsewhere. entire structural grid network in some forms of mechanical
ceiling suspension systems (Fig. 1b).
3.2.3 camber, n—the maximum component of deviation in
3.2.4.1 Discussion—The carrying channels are usually sus-
the horizontal plane of a main runner, cross runner, or wall
pended by hanger wires from the existing structure and the
molding where the centroidal axis of these structural compo-
main runners are then attached to the channels.
nents has been permanently deformed from end to end into the
shape of a simple regular curve during the manufacturing 3.2.5 ceiling suspension system, n—the entire network or
process (Fig. 2). grid of structural components, as defined by the ceiling
C635/C635M−22
FIG. 2Diagrams Showing Camber, Bow, and Twist
suspension system manufacturer, that provides support for runners. In some forms of mechanical ceiling suspension
acoustical ceiling tile, acoustical ceiling panels, lighting systems, the main runners are supported by hanger wires
fixtures, flexible sprinkler hose fittings and air diffusers. attached directly to the existing structure. In other forms, the
main runners (also referred to as “H” runners, “Z” bars, etc.)
3.2.6 cross runner, n—the secondary or cross beams of a
are installed perpendicular to carrying channels and are sup-
mechanical ceiling suspension system (Fig. 1, a and b). The
ported by specially designed sheet metal or wire clips attached
cross runners usually support only the acoustical tile. In some
to the carrying channels.
forms of suspension systems, however, the cross runners also
provide support for lighting fixtures, air diffusers, and other
3.2.11 nailing bar or furring bar, n—the continuous sheet
cross runners.
metal strips to which a backing board is attached using either
nails or screws (Fig. 1c). The nailing bars are installed
3.2.7 hanger wire, n—the wire employed to suspend the
acousticalceilingfromtheexistingstructure(woodjoists,steel perpendicular to and supported by the carrying channels.
bar joists, steel beams, concrete slabs, etc.) (Fig. 1).
3.2.12 non-interlocking, n—a ceiling system that does not
3.2.8 horizontal plane (of a structural component of a
comply with the specifications stated in the definition of
ceiling suspension system),n—a plane parallel to the plane of
interlocking.
the ceiling which passes through the centroidal axis of the
3.2.13 spline, n—a strip of metal or fiber inserted in the
member (Fig. 2).
kerfsofadjacentacousticaltiletoformaconcealedmechanical
3.2.9 interlocking, n—a ceiling system where the cross
joint seal (Fig. 1b).
runners are connected to the main runner or other cross
3.2.14 twist, n—the angle of rotation measured in a trans-
runners, or both, at intervals controlled by slots, holes, etc. in
verse plane between the two end cross sections of a main
the main runners.
runner, cross runner, or wall molding which has been perma-
3.2.10 main runner, n—the primary or main beams of the
nently deformed during the process of manufacturing (Fig. 2).
type of ceiling suspension system in which the structural
members are mechanically locked together (Fig. 1, a and b). 3.2.15 vertical plane (of a structural component of a ceiling
The main runners provide direct support for cross runners, and suspension system),n—a plane perpendicular to the plane of
may support lighting fixtures and air diffusers. In addition, the the ceiling which passes through the centroidal axis of the
acoustical tile may also be directly supported by the main member (Fig. 2).
C635/C635M−22
3.2.16 wall molding, n—the edge angles or channels of a in accordance with the test method described in Test Methods
mechanical ceiling suspension system that are attached to a E3090/E3090M, shall be listed as shown in Table 1 and Table
wall (Fig. 1, a and b). The wall molding provides support for 2.
the acoustical tile, main runners and cross runners that are
4.2 Cross runners shall be capable of carrying the load
located at the periphery of the ceiling.
specifiedbythemanufacturerwithoutexceedingthemaximum
allowable deflection equal to ⁄360 of its span.
4. Classification
4.3 Thedesignanddefinitionofthesuspensionsystemshall
4.1 The structural performance required from a ceiling
be the responsibility of the manufacturer. Included is selection
suspension system shall be defined by the specifying authority
of appropriate materials, metal thicknesses, dimensions of
in terms of a suspension system structural classification.
necessary component section configurations, design of special
4.1.1 The structural classification of ceiling suspension
hanger and assembly devices, and provision for whatever
systems shall be based on the load-carrying capacity of the
accessory items are needed to ensure satisfactory ceiling
main runners of the structural network. Load-carrying capacity
performance within the scope of this specification.
as used herein is based on the more stringent requirement of
4.3.1 System manufacturers may provide supplementary
esthetic acceptance rather than the less confining prevention of
data describing load deflection capabilities of main runners in
structural failure. The criterion is the arbitrary but widely
each classification for spans other than 4 ft [1200 mm].
established limit of deflection to ⁄360 of the span between
4.4 Where specialized loading conditions that are outside
supports.
thescopeofthisspecificationexist,themanufacturershouldbe
4.1.2 The load-carrying capacity shall be the maximum
consulted for his recommendations; and, he may furnish
uniformly distributed load (pounds force per linear foot [N/m])
engineering data as required. Specification or design of super-
that a simply supported main runner section having a span
structure anchors or fasteners are not the responsibility of the
lengthof4ft,0in.[1200mm]iscapableofsupportingwithout
1 ceiling system manufacturer unless specified by the ceiling
the mid-span deflection exceeding 0.133 in. [3.33 mm] or ⁄360
system manufacturer as part of the suspension system.
ofthe4ft,0in.[1200mm]spanlength,astestedinaccordance
with Test Methods E3090/E3090M.
5. Dimensional Tolerance
4.1.3 The structural classification or grade of ceiling sus-
pension systems shall be determined by the capability of main 5.1 Suspension system structural members shall conform to
runners or nailing bars to support a uniformly distributed load. the following tolerance requirements:
These classifications shall be: 5.1.1 Metal Thickness:
4.1.3.1 Light-Duty Systems, used where ceiling loads other 5.1.1.1 For steel systemsthethicknessofmetalusedinmain
than acoustical tile or lay-in panels are not anticipated, such as runners, cross runners, wall moldings, splines or nailing bars
residential and light commercial structures. shall be stated by the suspension system manufacturer in
4.1.3.2 Intermediate-Duty Systems, used where ceiling published literature. The thickness in thousandths of an inch
[mm
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: C635/C635M − 17 C635/C635M − 22
Standard Specification for
Manufacture, Performance, and Testing of Metal Suspension
Systems for Acoustical Tile and Lay-in Panel Ceilings
This standard is issued under the fixed designation C635/C635M; 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.
1. Scope
1.1 This specification covers metal ceiling suspension systems used primarily to support acoustical tile or acoustical lay-in panels.
1.2 Some suspension systems incorporate locking assembly details that enhance performance by providing some continuity or load
transfer capability between adjacent sections of the ceiling grid. The test methods of Test Methods E3090/E3090M referenced in
this specification do not provide the means for making a complete evaluation of continuous beam systems, nor for assessing the
continuity contribution to overall system performance. However, the test methods can be used for evaluating primary structural
members in conjunction with secondary members that interlock, as well as with those of noninterlocking type.
1.3 While this specification is applicable to the exterior installation of metal suspension systems, the atmospheric conditions and
wind loading require additional design attention to ensure safe implementation. For that reason, a specific review and approval
should be solicited from the responsible architect and engineer, or both, for any exterior application of metal suspension systems
in the construction of a new building or building modification.
1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each
system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the
two systems may result in non-conformance with the standard.
1.5 The following safety hazards caveat pertains only to the test methods described in this specification. This standard does not
purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to
establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior
to use.
1.6 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.
2. Referenced Documents
2.1 ASTM Standards:
B117 Practice for Operating Salt Spray (Fog) Apparatus
C634 Terminology Relating to Building and Environmental Acoustics
This specification is under the jurisdiction of ASTM Committee E33 on Building and Environmental Acoustics and is the direct responsibility of Subcommittee E33.04
on Application of Acoustical Materials and Systems.
Current edition approved Sept. 1, 2017May 15, 2022. Published September 2017June 2022. Originally approved in 1969. Last previous edition approved in 20132017 as
C635 – 13a.C635/C635M – 17. DOI: 10.1520/C0635_C0635M-17.10.1520/C0635_C0635M-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C635/C635M − 22
D1735 Practice for Testing Water Resistance of Coatings Using Water Fog Apparatus
E3090/E3090M Test Methods for Strength Properties of Metal Ceiling Suspension Systems
3. Terminology
3.1 Where these terms appear in this specification they shall have the meaning hereinTerms used in this standard are defined either
in Terminology C634 indicated as follows:or within this standard. The definition of terms explicitly given within this standard take
precedence over definitions given in Terminology C634. The definitions within Terminology C634 and this standard take
precedence over any other definitions of defined terms found in any other documents, including other documents that may be
referenced in this standard.
3.2 Definitions:Definitions of Terms Specific to This Standard:
3.2.1 backing board, n—a flat sheet of gypsum board to which acoustical tile is attached using adhesive, screws, staples, or other
suitable means (Fig. 1c).
3.2.2 bow, n—the maximum component of deviation in the vertical plane of a main runner, cross runner, or wall molding where
the centroidal axis of these structural components has been permanently deformed from end to end into the shape of a simple
regular curve during the manufacturing process (Fig. 2).
3.2.2.1 Discussion—
The meanings for bow and camber given here may differ from those applied elsewhere.
3.2.3 camber, n—the maximum component of deviation in the horizontal plane of a main runner, cross runner, or wall molding
where the centroidal axis of these structural components has been permanently deformed from end to end into the shape of a simple
regular curve during the manufacturing process (Fig. 2).
3.2.4 carrying channel, n—metal section that supports the entire structural grid network in some forms of mechanical ceiling
suspension systems (Fig. 1b).
3.2.4.1 Discussion—
The carrying channels are usually suspended by hanger wires from the existing structure and the main runners are then attached
to the channels.
3.2.5 ceiling suspension system, n—the entire network or grid of structural components, as defined by the ceiling suspension
system manufacturer, that provides support for acoustical ceiling tile, acoustical ceiling panels, lighting fixtures, flexible sprinkler
hose fittings and air diffusers.
3.2.6 cross runner, n—the secondary or cross beams of a mechanical ceiling suspension system (Fig. 1, a and b). The cross runners
usually support only the acoustical tile. In some forms of suspension systems, however, the cross runners also provide support for
lighting fixtures, air diffusers, and other cross runners.
3.2.7 hanger wire, n—the wire employed to suspend the acoustical ceiling from the existing structure (wood joists, steel bar joists,
steel beams, concrete slabs, etc.) (Fig. 1).
3.2.8 horizontal plane (of a structural component of a ceiling suspension system),n—a plane parallel to the plane of the ceiling
which passes through the centroidal axis of the member (Fig. 2).
3.2.9 interlocking, n—a ceiling system where the cross runners are connected to the main runner or other cross runners, or both,
at intervals controlled by slots, holes, etc. in the main runners.
3.2.10 main runner, n—the primary or main beams of the type of ceiling suspension system in which the structural members are
mechanically locked together (Fig. 1, a and b). The main runners provide direct support for cross runners, and may support lighting
fixtures and air diffusers. In addition, the acoustical tile may also be directly supported by the main runners. In some forms of
mechanical ceiling suspension systems, the main runners are supported by hanger wires attached directly to the existing structure.
In other forms, the main runners (also referred to as “H” runners, “Z” bars, etc.) are installed perpendicular to carrying channels
and are supported by specially designed sheet metal or wire clips attached to the carrying channels.
C635/C635M − 22
FIG. 1 Three Types of Ceiling Suspension Systems Showing All Components
3.2.11 nailing bar or furring bar, n—the continuous sheet metal strips to which a backing board is attached using either nails or
screws (Fig. 1c). The nailing bars are installed perpendicular to and supported by the carrying channels.
3.2.12 non-interlocking, n—a ceiling system that does not comply with the specifications stated in the definition of interlocking.
3.2.13 spline, n—a strip of metal or fiber inserted in the kerfs of adjacent acoustical tile to form a concealed mechanical joint seal
(Fig. 1b).
C635/C635M − 22
FIG. 2 Diagrams Showing Camber, Bow, and Twist
3.2.14 twist, n—the angle of rotation measured in a transverse plane between the two end cross sections of a main runner, cross
runner, or wall molding which has been permanently deformed during the process of manufacturing (Fig. 2).
3.2.15 vertical plane (of a structural component of a ceiling suspension system),n—a plane perpendicular to the plane of the
ceiling which passes through the centroidal axis of the member (Fig. 2).
3.2.16 wall molding, n—the edge angles or channels of a mechanical ceiling suspension system that are attached to a wall (Fig.
1, a and b). The wall molding provides support for the acoustical tile, main runners and cross runners that are located at the
periphery of the ceiling.
4. Classification
4.1 The structural performance required from a ceiling suspension system shall be defined by the specifying authority in terms of
a suspension system structural classification.
4.1.1 The structural classification of ceiling suspension systems shall be based on the load-carrying capacity of the main runners
of the structural network. Load-carrying capacity as used herein is based on the more stringent requirement of esthetic acceptance
rather than the less confining prevention of structural failure. The criterion is the arbitrary but widely established limit of deflection
to ⁄360 of the span between supports.
4.1.2 The load-carrying capacity shall be the maximum uniformly distributed load (pounds force per linear foot [N/m]) that a
simply supported main runner section having a span length of 4 ft, 0 in. [1200 mm] is capable of supporting without the mid-span
deflection exceeding 0.133 in. [3.33 mm] or ⁄360 of the 4 ft, 0 in. [1200 mm] span length, as tested in accordance with Test Methods
E3090/E3090M.
C635/C635M − 22
4.1.3 The structural classification or grade of ceiling suspension systems shall be determined by the capability of main runners
or nailing bars to support a uniformly distributed load. These classifications shall be:
4.1.3.1 Light-Duty Systems, used where ceiling loads other than acoustical tile or lay-in panels are not anticipated, such as
residential and light commercial structures.
4.1.3.2 Intermediate-Duty Systems, used where ceiling loads other than acoustical tile or lay-in panels (light fixtures, air diffusers,
etc.) are anticipated, such as ordinary commercial structures.
4.1.3.3 Heavy-Duty Systems, used where the quantities and weights of ceiling fixtures (lights, air diffusers, etc.) are greater than
those for an ordinary commercial structure.
4.1.4 For the purpose of determining the structural classification of main runner members as covered in 4.1.2, their simple-span,
minimum load-carrying capabilities, when tested in accordance with the test method described in Test Methods E3090/E3090M,
shall be listed as shown in Table 1 and Table 2.
4.2 Cross runners shall be capable of carrying the load specified by the manufacturer without exceeding the maximum allowable
deflection equal to ⁄360 of its span.
4.3 The design and definition of the suspension system shall be the responsibility of the manufacturer. Included is selection of
appropriate materials, metal thicknesses, dimensions of necessary component section configurations, design of special hanger and
assembly devices, and provision for whatever accessory items are needed to ensure satisfactory ceiling performance within the
scope of this specification.
4.3.1 System manufacturers may provide supplementary data describing load deflection capabilities of main runners in each
classification for spans other than 4 ft [1200 mm].
4.4 Where specialized loading conditions that are outside the scope of this specification exist, the manufacturer should be
consulted for his recommendations; and, he may furn
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