E580 401 Suspension Syst For Acoustical Lay In Ceilings Seismic Des Cat D E And F 2013

User Manual: E580

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NWCB Technical Document

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Suspension Systems for Acoustical Lay-in Ceilings

Seismic Design Categories D, E & F

SUSPENDED CEILINGS

401

12/13

This document has been revised based on current Building Code standards. In all buildings, other than structures classied as

essential facilities, suspended ceilings installed in accordance with the prescriptive provisions of the 401 document are

deemed to comply with the current building code interpretation.

This document provides the IBC-2012 referenced standards for the installation of suspension systems for acoustical lay-in

ceilings. Incorporation of this document will provide a more uniform standard for installation and inspection. This document is

designed to accomplish the intent of the International Building Code (IBC) with regard to the requirements for seismic design

category D, E and F for suspended ceilings and related items. Unless supported by engineering, the suspension system shall be

installed per these requirements and those of the referenced documents. Manufacturers’ recommendations should be followed

where applicable.

General Recommendations

• Referenced sources per hierarchy: 2012 International Building Code (IBC), American Society of Civil Engineers

(ASCE 7-10), American Society of Testing Materials (ASTM C 635, ASTM C 636, ASTM E 580/E 580M), and

Ceilings and Interior Systems Construction Association (CISCA).

• Partitions that are tied to the ceiling and all partitions greater than 6 feet in height shall be laterally braced to the

structure. Bracing shall be independent of the ceiling splay bracing system. Source: ASCE 7-10 Section 13.5.8.1

• For further information on bracing of non-load bearing partitions refer to NWCB Technical Document #200-501.

• All main beams are to be Heavy Duty (HD). Source: ASTM E580 Section 5.1.1

• Ceilings less than or equal to 144 ft2 and surrounded by walls connected to the structure above are exempt from

the seismic design requirements. Source ASTM E580 Section 1.4

• These recommendations are intended for suspended ceilings and related

components in areas that require resistance to the effects of earthquake motions.

Source: ASTM E580 Section 3.2

• All wire ties are to be three tight turns around itself within three inches. Twelve gage

Hanger wire spaced 4 foot on center (gure 1). Source: ASTM C636 Section 2.3.4

• Changes in ceiling planes will require positive bracing. Source: ASTM E580 Section 5.2.8.6

maximum 3"

(76mm)

gure 1

PAGE 1 OF 4

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EMT CONDUIT

½" EMT conduit up to 5' 10"

¾" EMT conduit up to 7' 8"

1" EMT conduit up to 9' 9"

METAL STUDS

Single 15⁄8" metal stud (20 gage) up to 12' 0"

Back-to-back 15⁄8" metal stud

(20 gage)

up to 15' 0"

Single 2 ½" metal stud (20 gage) up to 13' 6"

Back-to-back 2 ½" metal stud (25 gage) up to 15' 0"

gure 3

Maximum Recommended Lengths for

Vertical Struts

45º or less

45º or less 45º or less

45º or less

12 gage

splayed

brace

wires

Main beamCross tee

gure 2

Lateral force Bracing

Note: Plenum areas greater than 15' 0" will require engineering

calculations.

Source: Portland Building Department

maximum 8" (202 mm)

WALL

minimum

2" (50 mm)

gure 4a

Attached Wall Molding Requirements

gure 4b

Unattached Wall Molding Requirements

maximum 8" (202 mm)

WALL

minimum

2" (50 mm)

minimum

3/4" (19 mm)

at unattached walls

Speader bar or

other suitable

system required to

keep perimeter

compents from

spreading apart

Lateral Force Bracing (gures 2 and 3)

• Ceilings constructed of screw-or-nail-attached gypsum board on

one level that are surrounded by and connected to walls or softs

that are laterally braced to the structure above are exempt from

seismic design requirements. Source: ASCE 7-10 Section 13.5.6.2.2 Exception 2,

ASTM E580 Section 1.7

• Ceiling areas of 1000 ft2 or less shall be exempt from later force

bracing requirements. Source: ASTM E580 Section 1.6

• Lateral force bracing is the use of vertical struts (compression

posts) and splay wires (see gure 2).

• Lateral Force Bracing shall be 12 feet on center (maximum) and

begin no farther than 6 feet from walls. Source: ASTM E580 Section 5.2.8.2

• Seismic splay wires are to be four 12 gage wires attached to the

main beam. Wires are arrayed 90° from each other and at an

angle not exceeding 45° from the plane of the ceiling. Source: ASTM

E580 Section 5.2.8.2

• Seismic splay wires shall be attached to the grid and to the

structure in such a manner that they can support a design load of

not less than 200 pounds or the actual design load, with a safety

factor of 2, whichever is greater (gure 6b). Source: CISCA zones 3-4

• Power Actuated Fasteners (PAF’s), when used for seismic

application as part of the prescriptive path in Seismic Design

Categories D, E and F, shall have an ICC-ES approval for seismic

applications and shall require “special inspection” irrespective of

the type of occupancy category the structure is in. PAF anchors

for kicker wires (splayed wires installed for purposes other than

seismic restraint) are exempt from this requirement. Source: State of

Oregon, Building Codes Division

• Splay wires are to be within 2 inches of the connection of the

vertical strut to suspended ceiling. Source: ASTM E580 Section 5.2.8.2

• Rigid bracing may be used in lieu of splay wires. Source: ASTM E580

Section 5.2.8.4

• Ceilings with plenums less than 12 inches to structure are not

required to have lateral force bracing. Source: Portland Building Department

• Vertical struts must be positively attached to the suspension

systems and the structure above. Source: ASTM E580 Section 5.2.8.2

• The vertical strut may be EMT conduit, metal studs or a proprietary

compression post (see gure 3).

Wall Moldings (gures 4a and 4b)

• Wall moldings (perimeter closure angles) are required to have a

horizontal ange 2 inches wide. One end of the ceiling grid shall

be attached to the wall molding, the other end shall have a ¾ inch

clearance from the wall and free to slide. Source: ASTM E580 Section 5.2.2,

Section 5.2.3

• Where substantiating documentation has been provided to the

local jurisdiction, perimeter clips may be used to satisfy the

requirements for the 2-inch closure angle. Source: State of Oregon, Building

Codes Division

• The grid shall be attached at two adjacent walls (pop rivets or

approved method). Softs extending to a point at least level

with the bottom plane of the grid and independently supported

and laterally braced to the structure above are deemed to be

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3" (76 mm)

minimum

45º angle

minimum

45º angle

maximum 8"

plumb 1/6

gure 5b • Countersloping

gure 5a

45º

Splayed seismic bracing wire attachment

drill-in expansion anchor

Structural concrete

Steel strap 1" wide x 2" long x

12 gage minimum

3 turns

Splayed seismic bracing wire

Vertical hanger wire attachment

Shot-in anchor

Structural concrete

Ceiling clip

3 turns

Vertical hanger wire

3/4"

5/8"

max.

gure 6a

gure 6b

equivalent to walls. Source: State of Oregon, Building Codes Division, ASTM E580 Section

5.2.3, Section 5.2.9.1

Spreader Bars (gure 4b)

• Terminal ends of main runners and cross members shall be tied

together or have some other approved means to prevent their

spreading. Stabilizer bars, cross tees or other means to prevent

spreading shall occur within 8 in. of each wall. Source: ASTM E580 Section 5.2.4

• Spreader bars are not required at perimeters where runners are

attached directly to closure angles.

• Spreader bars are not required if a 90 degree intersecting cross or main

is within 8 inches of the perimeter wall.

• Where substantiating documentation has been provided to the local

jurisdiction, perimeter clips may be used to satisfy the requirements for

spreader bars. Source: State of Oregon, Building Codes Division

Hanger (Suspension) Wires (gures 5a and 5b)

• Hanger and perimeter wires must be plumb within 1 in 6 unless (gure 5a)

counter sloping wires are provided (gure 5b). Source: ASTM C636 Section 2.1.4

• Hanger wires shall be 12 gage and spaced 4 feet on center or 10 gage

spaced 5 feet on center. Source: ASTM C636 Section 2.1

• Any connection device at the supporting construction shall be capable

of carrying not less than 100 pounds. Source: CISCA zones 3-4

• Powder Actuated Fasteners (PAFs) are an approved method of

attachment for hanger wires. Source: State of Oregon, Building Codes Division

• Terminal ends of each main beam and cross tee must be supported

within 8 inches of each wall with a perimeter wire (see gure 4 & 5 a).

Source: ASTM E580 Section 5.2.6

• Wires shall not attach to or bend around interfering material or

equipment. A trapeze or equivalent device shall be used where

obstructions preclude direct suspension. Trapeze suspensions shall

be sized to resist the dead load and lateral forces appropriate for the

seismic category. Source: ASTM E580 Section 5.2.7.4

Electrical xtures

• Light xtures weighing less than 10 pounds shall have one 12 gage

hanger wire connected from the xture to the structure above. This wire

may be slack. Source: ASTM E580 Section 5.3.4

• Light xtures weighing more than 10 pounds and less than 56 lbs. shall

have two 12 gage wires attached at opposing corners of the light xture to

the structure above. These wires may be slack. Source: ASTM E580 Section 5.3.5

• Light Fixtures weighing more than 56 lbs. shall be supported directly

from the structure above by approved hangers. Source: ASTM E580 Section 5.3.6

• Pendant mounted xtures shall be directly supported from the structure

above using a 9 gage wire or an approved alternate support without

using the ceiling suspension system for direct support. Source: ASTM E580

Section 5.3.7

• Tandem xtures may utilize common wires.

Mechanical Services

• Terminals or services weighing less than 20 lbs. shall be positively attached

to the ceiling suspension main runners or to cross runners that have the

same carrying capacity as the main runners. Source: ASTM E580 Section 5.4.1

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• Terminals or services weighing 20 lbs. but not more

than 56 lbs. shall have, in addition to 5.4.1, two 12 gage

wires connecting them to the ceiling system hangers or

the structure above. These wires may be slack. Source:

ASTM E580 Section 5.4.2

• Terminals or services weighing more than 56 lbs. shall

be supported directly from the structure above by

approved hangers. Source: ASTM E580 Section 5.4.3

Seismic Separation Joints (gure 7)

• For ceiling areas exceeding 2,500 square feet, a

seismic separation joint or full height wall partition that

breaks the ceiling shall be provided unless analyses

are performed of the ceilings bracing system, closure

angles and penetrations to provide sufcient clearance.

Source: ASCE 7-10 Section 13.5.6.2.2 b

• The layout and location of the seismic separation

joint shall be per the designer of record and noted on

the plans. If a seismic separation joint is required by

the designer, the designer may use the generic joint

detailed in this document or a proprietary joint. The

amount of free movement (gap design) shall be a

minimum of ¾ inch. Source: State of Oregon, Building Codes Division

• In lieu of seismic separation joints, the ceiling may be

divided into areas less than 2500 square feet by the use

of partitions or softs as follows: partitions shall extend a

minimum of 6 inches above the level of the plane of the

grid and shall be independently braced to the structure

above. Softs shall extend to a point at least level with

the bottom plane of the grid and shall be independently

supported and laterally braced to the structure above.

Source: State of Oregon Building Codes Division, ASTM E580 Section 5.2.9.1

Sprinklers

• For ceilings without rigid bracing, sprinkler head

penetrations shall have a 2 inch oversize ring, sleeve or

adapter through the ceiling tile to allow free movement of

at least 1 inch in all horizontal directions. Flexible head

design that can accommodate 1 inch free movement shall

be permitted as an alternate. Source: ASTM E580 Section 5.2.8.5

Flange

Pop

Rivet

3/4"

minimum

gure 7

Glossary for this Document (regional terminology may vary)

CROSS TEES The cross member that interlock with the main

beams, also known as cross runners or cross T-bars.

DIFFUSER A circular or rectangular metal grill used for the

passage of air from a ducted system.

ESSENTIAL SERVICE BUILDINGS Any buildings designed to be

used by public agencies as a re station, police station, emer-

gency operations center, State Patrol ofce, sheriff’s ofce, or

emergency communication dispatch center.

GRID The main beams and cross tees of the suspension system.

HANGER WIRE 10 or 12 gage soft annealed wire used as pri-

mary support for the grid system. Also called suspension wires.

LATERAL FORCE BRACING The bracing method used to prevent

ceiling uplift or restrict lateral movement during a seismic event.

Lateral force bracing consists of vertical struts and splay wires.

MAIN BEAM The primary suspension member supported by

hanger wires, also known as the main runner, carrying tee,

carrying runner or mains.

MOLDING/CLOSURE ANGLE A light gauge metal angle or chan-

nel fastened to the perimeter wall or partition to support the

perimeter ends of an accoustical ceiling grid.

PERIMETER CLIPS Proprietary angle bracket attached directly

to the wall molding/closure angle which allows for ¾” move-

ment in the event of seismic activity and interlocks properly

with ends of grid system.

PERIMETER WIRES Hanger wires placed within eight inches of

the surrounding walls.

PLENUM The space above a suspended ceiling.

SLACK WIRE A 12 gage wire that is not tight or taut.

SPREADER or SPACER BAR A bar with notches to prevent the

suspension system from separating, also called a stabilizer

bar.

SPLAY WIRES Wires installed at an angle rather than perpen-

dicular to the grid.

VERTICAL STRUTS The rigid vertical member used in later-

al force bracing of the suspension system. Also known as

compression posts, seismic pods, seismic struts. Common

materials are electrical conduit (EMT), metal studs or propri-

etary products.

The NWCB has been serving the construction industry for over forty years. It is recognized as a technical authority, educational body and spokesperson for the wall and ceiling

industry. It provides services to architects and the construction community on all matters relating to the diversied wall and ceiling industry. As the industry’s development

and coordination organization, the NWCB saw the need to establish a document to provide clarication and the intent of NEHRP (National Earthquake Hazards Reduction

Program) an agency of FEMA (Federal Emergency Management Agency). It is meant to serve as a set of recommendations and is not intended for any specic construction

project. This technical document is to serve as a guideline and it is not intended for any specic construction projects. NWCB makes no express or implied warranty or

guarantee of the techniques, construction methods or materials identied herein.

E580 401 Suspension Syst For Acoustical Lay In Ceilings Seismic Des Cat D E And F 2013

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