CPA T-Bar Guidelines Page 1 of 15

Revision Date: 10/2012

General Requirements/Checklist for: Commercial

SUSPENDED CEILING SYSTEMS INSPECTION

City of Palo Alto (CPA) Building Inspection Division

Inspection Request Line: 650 329-2496

Building Division Inspection Code IVR# 304

Codes/Standards Enforced: 2010 CBC, ASCE 7-50, ASTM C 635, 636, CISCA 3-4 Palo Alto Municipal Code (PAMC)

The information provided in this document is general and intended as a guide only. Each project is unique and additional requirements may be enforced as deemed appropriate.

REQUIRED ITEMS All existing tenant improvement suspended ceiling systems installed prior to January 1,

2008 in areas affected by renovation, structural repair, or alterations must be upgraded to meet seismic requirements set forth in CISCA 3-4/UBC Standard 47-18. (See CISCA Guidelines for Seismic Upgrade requirements following checklist)

PLANS/SHOP DRAWINGS/ICC ES REPORT Contractor shall provide City of Palo Alto Inspector with engineered “heavy duty” suspended

ceiling system plans/shop drawings/manufacturer’s installation requirements at time of inspection.

Plan must include engineering specifications for compression struts, wall attachments, and layout for seismic joints when areas in excess of 2500 square feet.

Provide inspector with current ICC ES Report for suspended ceiling system.

SPECIAL INSPECTION City of Palo Alto adopted policy #15 on 07/09/2009 of ICC Tri-Chapter Uniform Code

Committee - Special Inspection is not required for suspended ceiling.

MINIMUM CODE REQUIREMENTS Suspended Ceilings (2010 CBC 2506.2.1/ASCE 7-05 13.5.6)

o Seismic Design Categories D requirements for Suspended Ceiling Systems shall be designed and installed in accordance with ASTM C635, ASTM C636, and the CISCA for Seismic Zones 3-4 as modified by the following: A heavy duty T-bar grid system shall be used. The width of the perimeter supporting closure angle shall be not less than 2 inches.

Approved perimeter seismic clips may be used in lieu of 2 inch wall angle and shall be installed per manufacturer’s instruction and ICC-ESR reports information.

In each orthogonal (orthogonal means "involving right angles") horizontal direction, one end of the ceiling grid shall be attached to the closure angle.

The other end in each horizontal direction shall have a 0.75 inches clearance from the wall and shall rest upon and be free to slide on a closure angle.

o For ceiling areas exceeding 1,000 ft2, horizontal restraint of the ceiling to the structural system shall be provided. The tributary areas of the horizontal restraints shall be approximately equal.

(Manufacturer may required vertical post every 12 square feet) EXCEPTION: Rigid braces are permitted to be used instead of diagonal splay wires. Braces and attachments to the structural system above shall be adequate to limit

relative lateral deflections at point of attachment of ceiling grid to less than 0.25 inch for the loads prescribed in Section 13.3.1.

CPA T-Bar Guidelines Page 2 of 15 MINIMUM CODE REQUIREMENTS (continued)

o For ceiling areas exceeding 2,500 ft2, a seismic separation joints or full height partition that breaks the ceiling up into areas not exceeding 2,500 ft2 shall be provided EXCEPTION Structural analyses of the ceiling bracing system for the prescribed seismic forces that

demonstrate ceiling system penetrations and closure angles provide sufficient clearance to accommodate the anticipated lateral displacement.

o Except where rigid braces are used to limit lateral deflections, sprinkler heads and other penetrations shall have a 2 inches oversize ring, sleeve, or adapter through the ceiling tile to allow for free movement of at least 1 inch in all horizontal directions. Alternatively, a swing joint that can accommodate 1 inch of ceiling movement in all

horizontal directions is permitted to be provided at the top of the sprinkler head extension. (see example illustrations for flex drops)

o Changes in ceiling plan elevation shall be provided with positive bracing. (See example illustrations below)

o Cable trays and electrical conduits shall be supported independently of the ceiling per ASCE 7-05 chapter 13 requirements.

o Integral Construction. As an alternate to providing large clearances around sprinkler system penetrations through ceiling systems, the sprinkler system and ceiling grid are permitted to be designed and tied together as an integral unit. (ASCE 7-05 13.5.6.3) Such a design shall consider the mass and flexibility of all elements involved, including

the ceiling system, sprinkler system, light fixtures, and mechanical (HVAC) appurtenances. Such design shall be performed by a registered design professional.

Perimeter hangers - terminal ends of each cross runner and main runner shall be supported independently a maximum of 8” inches from each wall or ceiling with number12 gage wire or approved wall support.

Vertical wires shall be attached to the suspension member and to the support above with a minimum of three turns.

Trapeze or equivalent device may be used where obstruction precludes direct suspension. Seismic separation joints shall be installed per manufacturer’s specifications & approved plans. Vertical hangers: Suspension wires shall not be smaller than #12 gauge spaced at 4’ on

center or #10 gauge at 5’ on center along each main runner. Compression strut/seismic posts are typically required every 144 sq. ft., starting a maximum

6’-0” from perimeter with seismic wires (4) directions @ max. 45 degrees from horizontal. Partitions Tied To Suspended Ceilings (ASCE 7-05 13.8)

o General. Partitions that are tied to the ceiling and all partitions greater than 6ft in height shall be laterally braced to the building structure. Such bracing shall be independent of any ceiling splay bracing. Bracing shall be spaced to limit horizontal deflection at the partition head to be

compatible with ceiling deflection requirements as determined in Section ASCE 7-05 13.5.6 for suspended ceilings and elsewhere in this section for other systems. EXCEPTION: Partitions that meet all of the following conditions: 1) The partition height does not exceed 9 ft. 2) The linear weight of the partition does not exceed the product of 10lb times the

height (ft) of the partition. 3) The partition horizontal seismic load does not exceed 5 psf.

CPA T-Bar Guidelines Page 3 of 15 Fire ratings shall comply with the requirements of the 2010 California Building Code chapter

7, UL listing, Office of the State Fire Marshal’s listing, and installation per the manufacturer’s suspended ceiling system installation manual. o The components and installation details must conform to the U.L. or SFM approval for the

design number specified. o Custom designs which combine components from different approved designs but have not

been tested as a complete assembly are not acceptable. o For schools and Essential Services Buildings, bracing assemblies are required for each 96

square feet. o The first bracing assembly is required not more than four (4) feet from each wall. o A minimum of one bracing assembly is required between any two adjacent expansion cut-

outs on runners being braced. Fire Separation Marking and Identification Requirements Fire walls, fire barriers, fire partitions, smoke barriers and smoke partitions or any

other wall required to have protected openings or penetrations shall be effectively and permanently identified with signs or stenciling. (2010 CBC section 703.6) O Such identification shall: Be located in accessible concealed floor, floor-ceiling or attic spaces; Be repeated at intervals not exceeding 30 feet measured horizontally along the wall or

partition; and Include lettering not less than 0.5 inch in height, incorporating the suggested wording:

"FIRE AND/OR SMOKE BARRIER-PROTECT ALL OPENINGS," or other wording. Exception: Walls in Group R-2 occupancies that do not have a removable decorative ceiling allowing access to the concealed space.

ABOVE CEILING INSULATION Concealed installation. Insulating materials, where concealed as installed in buildings of

any type of construction, shall have a flame spread index of not more than 25 and a smoke-developed index of not more than 450. (2010 CBC section 719.2) o Facings. Where such materials are installed in concealed spaces in buildings of Type III,

IV or V construction, the flame spread and smoke-developed limitations do not apply to facings, coverings, and layers of reflective foil insulation that are installed behind and in substantial contact with the unexposed surface of the ceiling, wall or floor finish. (2010 CBC 719.2.1) Exception: All layers of single and multilayer reflective plastic core insulation shall comply with

Section 2613. Exposed installation. Insulating materials, where exposed as installed in buildings of any

type of construction, shall have a flame spread index of not more than 25 and a smoke-developed index of not more than 450. (2010 CBC 719.3)

Surface insulation or other purposes shall be considered interior finish if they cover 10 percent or more of the wall or of the ceiling area, and shall not be considered decorative materials or furnishings. (2010 CBC 806.1) o Paper faced insulation is not permitted in exposed above ceiling areas, the open side of

furred spaces, and ventilated interstitial spaces due to the potential of embers igniting the paper.

o Quilted foil-backed or un-faced fiberglass batts and blankets are better suited to conditions of potential fire hazards.

o Use approved quilted foil-backed insulation such as “Reflectix Insulation” in areas where a vapor barrier is required and use as a fix when paper back insulation is exposed.

CPA T-Bar Guidelines Page 4 of 15 ELECTRICAL Abandoned cables are not permitted to remain. CEC 800.52 (b Junction boxes and similar enclosures shall be accessible and shall have required working

clearances CEC 314.29, 110.26(a) Cables and raceways shall not be supported by ceiling grids. CEC 300.11(a) CEILING MOUNTED AIR TERMINALS Air terminals weighing less than 20 pounds shall be positively attached using sheet metal

screws. Minimum of two screws are to be installed on each side of the terminal, near the corners, and fastened into the main runners.

Air terminals weighing 20 lbs but not more than 56 pounds, in addition to the above, shall have two #12-gage hangers connected from the terminal or service to the ceiling system hangers or to the structure above. These wires may be installed with limited slack.

Air terminals weighing more than 56 pounds shall be supported directly from the structure above by approved hangers.

RETURN AIR PLENUMS Verify that all materials meet the applicable flame spread rating for return air plenums and

ducts noted as “plenum rated”. Equipment and devices shall be permitted only when necessary for their direct action upon, or

sensing of, the contained air. CEC 300.22 (b) Verify that fire damper is clear and operational. CBC Communication plenum rated cable (CMP) shall be listed as suitable for use in ducts,

plenums and listed as having adequate fire resistant and low smoke producing characteristics. CEC 800.179 (a), CEC 800.154 (a)

LIGHTING FIXTURE SUPPORTS Only “Heavy-Duty” systems listed for Seismic Design Category D shall be used in the City of

Palo Alto. All lighting fixtures shall be positively attached to the suspended ceiling system with 4 screws -

typically one at each corner. Wires required to the fixture:

o Fixture less than 56 lbs: two no. 12-gage hangers connected from the fixture housing to the structure above. These wires may be installed with limited slack.

o Fixtures more than 56 lbs shall be supported directly from the structure above by approved hangers.

o Pendant Hung Fixtures shall be supported directly from the structure above with #9 gauge wire without using the ceiling suspension system for direct support.

ASCE 7-05 CHAPTER 13 SEISMIC BRACING EXEMPTIONS FOR PIPING SYSTEMS

The exemptions that apply specifically to seismic bracing for piping systems are covered in Section 13.6.8 of ASCE 7-05. The provisions of this section do not cover elevator system piping which is covered in Section

13.6.10 of ASCE 7-05. Also not covered in this section is fire protection piping. Fire protection piping will be covered

in a separate publication. The piping considered in this section is assumed to be high-deformability piping.

o This implies pipes made from ductile materials that are joined by welding, brazing, or groove type couplings, similar to Victaulic couplings, where the grooves in the pipe have been roll formed rather than cut.

CPA T-Bar Guidelines Page 5 of 15

ASCE 7-05 CHAPTER 13 SEISMIC BRACING EXEMPTIONS FOR PIPING SYSTEMS (continued)

Limited deformability piping on the other hand, would be pipes made of ductile materials that are joined by threading, bonding, or the use of groove type couplings where the grooves in the pipe have been machine cut. o Low deformability piping would be comprised of pipes made from relatively brittle materials

such as cast iron or glass. The 12 inch Rule (ASCE 7-05 Section 13.6.8-1]1): No restraints will be required for piping that meets the requirements of the 12 inch Rule for

the entire piping run. The 12 inch Rule will be said to apply to a piping run if: o The piping is supported by rod hangers. o For single clevis supported pipe, all of the hangers in the piping run are 12 inches or less in

length from the top of the pipe to the supporting structure. o For trapeze supported pipe, all of the hangers in the piping run are 12 inches or less in

length from the top of the trapeze bar to the supporting structure. The past practice by SMACNA and other recognized authorities in the industry to call for the connection between the hanger and the supporting structure to be “non-moment generating”. This means that the connector must be one that allows the piping run to swing freely on its

hangers without introducing a bending moment in the hanger. o There must be sufficient space around the piping run to accommodate the expected motion

of the pipe as it sways back and forth with the earthquake motion in the building. o Connections between the piping and the interfacing components must be designed and/or

selected to accept the full range of motion expected for both the pipe and the interfacing component.

Single Clevis Supported Pipe in Seismic Design Categories D (ASCE 7-05 Sections 13.6.8-2a and 13.6.8-2c) For single clevis supported piping in buildings assigned to Seismic Design Categories D for

which the Component Importance Factor is equal to 1.5, and for which the nominal size is 1 inch or less; no seismic restraint is required.

For single clevis supported piping in buildings assigned to Seismic Design Categories D for which the Component Importance Factor is equal to 1.0, and for which the nominal size is 3 inches or less; no seismic restraint is required.

CPA T-Bar Guidelines Page 6 of 15

Exemptions for Trapeze Supported Pipe per VISCMA Recommendations

Neither ASCE 7-98-02 nor ASCE 7-05 specifies how the piping is to be supported. The point is that many pipes of the exempted size may be supported on a common trapeze

bar using hanger rods of the same size as would be specified for a single clevis supported pipe. o Keep in mind that the purpose of the seismic restraints is to make sure the pipe moves

with the building. o The amount of force that the hanger rod must carry will be a direct function of the weight

of pipe being supported. o There must be some limit to how much weight a trapeze bar can support for a given

hanger rod size before seismic restraint is required. VISCMA (Vibration Isolation and Seismic Control Manufacturer’s Association) has investigated this issue and can make the following recommendations on the application of the exemptions in Sections 5.4 and 5.5 above to trapeze supported pipe, www.viscma.com. The following basic provisions must apply:

o The hangers must be ASTM A36 all-thread rod. o The threads must be roll formed. o The pipes must be rigidly attached to the hanger rods. o Provisions must be made to avoid impact with adjacent pipe, duct, equipment, or building

structure, or to protect the pipe from such impact. Trapeze Supported Pipe in Seismic Design Category D: (ASCE 7-05 Sections 13.1.4-5, 13.6.8-2a, and 13.6.8-2c) For trapeze supported piping in buildings assigned to Seismic Design Category D, which have a

Component Importance Factor equal to 1.5, and for which the nominal size is 1 inch or less, no seismic restraint is required if: o The trapeze bar is supported by 3/8-16 UNC, or larger, hanger rods. o The maximum hanger spacing is 7 ft. on center. o The total weight supported by the trapeze bar is 4 lbs/ft or less.

For trapeze supported piping in buildings assigned to Seismic Design Category D, which have a Component Importance Factor equal to 1.0, and for which the nominal size is 3 inches or less, no seismic restraint is required if: o The trapeze bar is supported by ½”-13 UNC, or larger, hanger rods. o The maximum hanger spacing is 10 ft. on center. o The total weight supported by the trapeze bar is 25 lbs/ft or less.

The Seismic Design Category to which the project has been assigned must be known. o This should be noted on the issued permit plans. o The design professional responsible for the piping system must assign an appropriate

Component Importance Factor to the system. As a sidebar to the previous statement, it should be noted that the specification for the building may increase the Seismic Design Category in order to ensure an adequate safety margin and the continued operation of the facility. This is a common practice with schools, government buildings, and certain manufacturing facilities.

The building owner has the prerogative, through the specification, to require all of the piping systems to be seismically restrained. Careful attention to the specification must be paid, as some or all of the exemptions in this section may be nullified by specification requirements that are more stringent than those provided by the code.

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DETAILS

REFERENCES

STANDARDS

CPA T-Bar Guidelines Page 5 of 12

EXAMPLES OF DRYWALLL SUSPENDED CEILING SYSTEM - NO MIXING COMPONENTS

EXAMPLES OF DRYWALLL SUSPENDED CEILING SYSTEM - NO MIXING COMPONENTS

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EXAMPLES OF FLEXIBLE SPRINKLER SUSPENDED CEILING SYSTEM ATTACHMENTS

CPA T-Bar Guidelines Page 7 of 12

EXAMPLES OF SEISMIC CONNECTORS FOR SUSPENDED CEILING SYSTEMS

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EXAMPLES OF SEISMIC CONNECTORS FOR SUSPENDED CEILING SYSTEMS

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EXAMPLES OF SEISMIC CONNECTORS FOR SUSPENDED CEILING SYSTEMS

CPA T-Bar Guidelines Page 10 of 12 EXAMPLES OF SEISMIC CONNECTORS FOR SUSPENDED CEILING SYSTEMS

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CPA T-Bar Guidelines Page 12 of 12

rmcmani

Text Box

STANDARD FOR EXISTING SUSPENDED CEILING SYSTEM UPGRADES

U.B.C. STANDARD 47-18 T-BAR CEILING INSTALLATIONS

EXISTING SYSTEMS Systems installed prior to Jan 1, 2008 shall be upgraded to meet 1997 Standards 47-18.

UBC STANDARD 47-18 INSTALLATION REQUIREMENTS AND ILLUSTRATIONS

Part 11-1 ns tall a tlon Scope

Sec. 47.1808. This standard describes procedures for the installation of suspen­sion systems for acoustical tile and lay-in panels.

Installation of Components Sec. 47.1809. (a) Hangers. Hangers shall be attached to the bottom edge of the

wood joists or to the vertical face of the wood joists near the bottom edge. Bottom edge attachment devices shall be an approved type.

In concrete construction mount hangers using cast-in-place hanger wires, hanger inserts, or other hanger attachment devices shall be an approved type. If greater center-to-center distances than 4 feet 0 inch are used for the hangers, reduce the load-carrying capacity of the ceiling suspension system commensurate with the ac· tual center-to-center hanger distances used.

Hangers shall be plumb and shall not press against insulation covering ducts or pipes. If some hangers must be splayed, offset the resulting horizontal force by brac­ing, countersplaying or other acceptable means.

Hangers formed from galvanized sheet metal stock shall be suitable for suspend­ing carrying channels or main runners from an existing structure provided that the hangers do not yield, twist or undergo other objectionable movement.

Wire hangers for suspending carrying channels or main runners from an existing structure shall be prepared from a minimum of No. 12-gage, galvanized, soft-an­nealed, mild steel wire.

Special attachment devices that support the carrying channels or main runners shall be approved to support five times the design load.

(b) Carrying Channels. The carrying channels shall be installed so that they are all level to within Y. inch i'n 12 feet.

Leveling shall be performed with the supporting hangers taut. Local kinks or bends shall not be made in hanger wires as a means of leveling car­

rying channels. In installations where hanger wires are wrapped around carrying channels, the

wire loops shall be tightly formed to prevent any vertical movement or rotation of the member within the loop.

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1988 EDITION 47-18

(c) Msin Runners. Main runners shall be installed so that they are all level lO

within Y. inch in 12 feet. Where main runners are supported directly by hangers, leveling shall be per­

formed with the support.ing hanger taut. Local kinks or bends shall not be made in hanger wires as a means of leveling

main runners. In installations where hanger wires are wrapped through or around main runners,

the wire loops shall be tightly wrapped and sharply bent. (d) Cross Runners. Cross runners shall be supported by either main runners or by

other cross runners to within X2 inch of the required center distances. This tolerance shall be noncumulative beyond 12 feet.

Intersecting runners shall form a right angle. The exposed surfaces of two intersecting runners shall lie within a vertical distance

of 0.015 inch of each other with the abutting (cross) member always above the con­tinuous (main) member.

(e) Splines. Splines used to form a concealed mechanical joint seal between adja­cent tiles shall be compatible with the tile kerf design so that the adjacent tile will be horizontal when installed. Where splines are longer than the dimension between edges of supporting members running perpendicular to the splines, place the splines so that they rest either all above or all below the main running members.

(f) Assembly Devices. Abutting sections of main runner shall be joined by means of suitable connections such as splices, interlocking ends, tab locks, pin locks, etc. A joint connection shall be judged suitable both before and after ceiling loads are im­posed if the joint provides sufficient alignment so that the exposed surfaces of two abutting main runners lie within a vertical distance of 0.015 inch of each other and within a horizontal distance of 0.0 IS inch of each other.

There shall be no visually apparent angular displacement of the longitudinal axis of one runner with respect to the other.

Assembly devices shall provide sufficient spacing control so that horizontal gaps between exposed surfaces of either abutting or intersecting members shall not exceed 0.020 inch.

Spring wire dips used for supporting main runners shall maintain tight contact between the main runners and the carrying channels when the ceiling loads are im­posed on the runners.

(g) Ceiling Fixtures. Fixtures installed in acoustical tile or lay-in panel ceilings shall be mounted in a manner that will not compromise ceiling performance.

Fixtures shall not be supported from main runners or cross runners if the weight of the fixtures causes the total dead load to exc~ed the deflection capability of the ceiling suspension system. In such cases, the fixture load shall be supported by sup­plemental hangers within 6 inches of each corner, or the fixture shall be separately supported.

Fixtures shall not be installed so that main runners or cross runners will be eccen­trically loaded except where provision is inherent in the system (or is separately pro­vided for) to prevent undesirable section rotation or displacement, or both. In any case, runners supporting ceiling fixtures shall not rotate more than 2 degrees after the fixture loads are imposed.

Where fixture installation would produce rotation of runners in excess of 2 degrees, install fixtures with the use of suitable accessory devices. These devices shall support the fixture in such a manner that the main runners and cross runners will be loaded symmetrically rather than eccentrically.

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47-18 U.B.C. STANDARDS

Part lll-Latmal Design Requirements

Scope

Sec. 47.1810. Snspencled ceiling which are designed and constructed to support ceiling panels or tiles, with or without lighting fixtures, ceiling mounted air terminals or other ceiling mounted services shall comply with the requirements of this standard.

EXCEPTIONS: I. Cci ling an· a of 14 4 square feet or less surrounded by walls which connect dir..:ctly to the stn1cture above shnll be exempt from the lateral load design requirements of these ~tandards.

2. Ceilings constr11ctrd of l~th and plaster or gypsum board. screw or nail attached to suspcndrd members tlmt support a ceiling on one level extending from wall to wall. I

Minimum Design Loads Sec 47.1811. (a) Lateral Forces. Such ceiling systems and their connections to the

building structure shall be designed and constructed to resist a lateral force specified in Chapter 23 of !he Uniform Building Code.

Where the ceiling system provides lateral support for nonbearing partitions, it shall be designed for the prescribed lateral force reaction from the partitions us specified in Section 47.1815.

Connection of lighting fixtures to the ceiling system shall be designed for a lateral force of 100 percent of the weight of the fixture in addition to the prescribed vertical loading as specified in Section 47.1813.

(b) Grill Members, Connectors anu Expansion Devices. The main runners and cross runners of the ceiling system and their splices, intersection connectors and expansion devices shall be designed and constructed to carry a mean ultimate test load of not less than 180 pounds or twice the actual load, whichever is greater, in tension with a 5-degree misalignment of the members in any direction, and in compression. In lieu of 5-degree misalignment, the load may be applied with a l-inch eccentricity on a sample not more than 24 inches long each side of the splice. The connections at splices and intersections all shall be of the mechanical interlocking type.

Where the composition or configuration of ceiling systems members or assemblies and their connections are such that calculations of their allowable load-carrying capacity cannot be made in accordance with established methods of analysis, their performance shall be established by test.

Evaluation of test results shall be made on the basis of the mean values resulting from tests of not fewer than three identical specimens, provided the deviation of any individual test result from the mean value does not exceed plus or minus I 0 percent. The allowable load­carrying capacity as determined \:ly test shall not exceed one half of the mean ultimate test value.

(c) Substantiation. Each ceiling systems manufacturer shall furnish lateral loading capacity and displac

1ement or elongation characteristics for his systems, indicating the

following: I. Maximum bracing pattern and minimum wire siz.es. 2. Tension and compression force capabilities of main runner splices, cross runner

connections and expansion devices. All tests shall be conducted by an approved testing agency.

Installation Sec. 47.1812. (a) Vertical Hangers. Suspension wires shall be not smaller than No. 12

gage spaced at ,1 feel on center or No. 10 gage at 5 feet on center along each main runner unless calculations justifying the incre<1sed spacing are provided.

1988 EDITION 47-18

Each vertical wire shall be attached to the ceiling suspension member and to the support above with a minimum of three turns. Any connection device at the supporting construe lion shall be capable of carrying not less than 100 pounds.

Suspension wires shall not hang more than l in 6 out-of-plumb unless countcrsloping wires are provided.

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 a minimum of back-to-back 11/4-inch cold-rolled channels for spans exceeding 48 inches.

(b) Perimeter Hangers. the terminal ends of each cross runner and main runner shall be supported independently a maximum of 8 inches from each wall or ceiling discontinuity with No. 12 gage wire or approved wall support. •

(c) Lateral Force Bracing. Where substantiating design caltulations are not provided, horizontal restraints shall be effected by four No. I 2 gauge wires secured to the main runner within 2 inches of the cross runner intersection and and splayed 90 degrees from each other at an angle not exceeding 45 degrees from the plane of the ceiling. A strut fastened to the main runner shall be extended to and fastened to the structural members supporting the roof or floor above. The strut shall be tH.lcquatc to resist the vertical component inutl~:ctl by the bracing wires. These horizontal restraint points shall be placed 12 feet on center in both directions with the first point within 6 feet from each wall. Attachment of the restraint wires to the structure above shall be adequate for the load imposed.

Lateral force bracing members shall be spaced a minimum of 6 inches from all horizontal piping or duct work that is not provided with bracing restraints for horizonta I forces. ·Bracing 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, whichever is greater, with a safety factor of 2.

(d) Perimeter Members. Unless perimeter members are a structural part of the approved system, wall angles or channels shall be considered as aesthetic closers and shall have no structural value assessed to themselves or their method of attachment to the walls. For tile ceilings, ends of main runners and .cross members shall be tied together to prevent their spreading.

(e) Attachment of Members to the Perimeter. To facilitate installation, main runners and cross runners may be attached to the perimeter member at two adjacent walls with clearance between the wall and the runners maintained at the other two walls or as otherwise shown or described for the approved system.

Lighting Fixtures Sec. 47.1813. Only "intermediate" and "heavy duty" c;eiling systems as defined in

Section 47.1802 may be used for the support of lighting fixtures. All lighting fixtures shall be positively attached to the suspended ceiling system. The

attachment device shall have a capacity of 100 percent of the lighting fixture weight acting in any direction.

When" intermediate" systems are used, No. 12 gage hangers shall be attached to the grid members within 3 inches of each corner of each fixture. Tandem fixtures may utilize common wires.

Where "heavy duty" systems are used, supplemental hangers are not required if a 48- inch modular hanger pattern is followed. When cross runners are used without supplemental hangers to support lighting fixtures, these c;ross runners must provide the same carrying capacity as the main runner.

Lighting fixtures weighing less than 56 pounds shall have, in addition to the require rnents

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47-18 U.B.C. STANDARDS

outlined above, two No. 12 gage hangers connected from the fixture housing to the structure above. These wires may be slack. . Lighting fixtures weighing 56 pounds or more shall be supported directly from the structure above by approved hangers.

Pendant-hung lighting fixtures shall be supported directly from the stnrcture above using No. 9 gage wire or approved alternate support wjthout using the ceiling suspension system for direct support.

Mechanical Services ~ t J..J • 2. 'S C.Q. f,2 1.-1..) "')' I\'-.)"tb

,.,, ... -' \i:~ ~ \A.A. A. 1 10 j2. \..-'.. tv IV ~ R.._ . ~nted air terminals or services weighing less' tthan 20

pounds shall be ositivel attache_<;!Jo the ceiling suspension main runners or to cro~.) runners with the same carrying cap.acity as the main runners.

Terminals or services weighing 20 pounds but not more than 56 pounds, in addi­tion to the above, shall have two No. J 2 gage hangers connected from the terminal or service to the ceiling system hangers or to the structure above. These wires may be slack.

Terminals or services weighing more than 56 pounds shall be supported directly from the structure above by approved hangers.

Partitions Sec. 47.1815. Where the suspended ceiling system is required to provide lateral

support for permanent or relocatable partitions, the connection of the partition to the ceiling system, the ceiling system members and their connections, and the lateral force bracing shall be designed to support the reaction force of the partition from prescribed loads applied perpendicular to the face of the partition. These partition reaction forces shall be in addition to the loads described in Section 47.181 J. Parti­tion connectors, the suspended ceiling system and the lateral force bracing shall all be engineered to suit the individual partition application and shall be shown or defined in the drawings or specifications.

Drawings and Specifications Sec. 47.1816. The drawings shall clearly identify all systems and shall define or

show all supporting details, lighting fixture attachment, lateral force bracing, parti­tion bracing, etc. Such definition may be by reference to this standard, or approved system, in whole or in part. Deviations or variations must be shown or defined in detail.

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