City of Medford Building Safety Department TOPIC: Wall and Ceiling Construction - IBC/25/#2 CODE: Structural Specialty Code: 2004 Edition REFERENCE: Section 803.9.1 Structural Specialty Code SUBJECT: An Alternative Method for the Installation Standards of Suspended Ceiling System and Lighting Fixtures QUESTION: What standards does the Building Safety Department use to review and inspect suspended ceiling systems? What are the standards for permit application? When existing ceilings must be upgraded? RESPONSE: The Building Safety Department accepts suspended ceiling systems which are either engineered or which comply with the prescriptive design standard as detailed below. I. NEW SUSPENDED CEILINGS - PRESCRIPTIVE DESIGN For buildings that are classified as either Category I or II buildings by Table 1604.5 in the Oregon Structural Specialty Code (OSSC), the Bureau will accept suspended ceilings that comply with the following prescriptive design standards without an engineer or architect approved design. A. Permit Application The permit application for a suspended ceiling to be installed to this prescriptive standard shall include three copies of manufacturer's data or ICC-ES Evaluation Reports identifying that the system is a heavy duty system conforming to the requirements of ASTM C635-00; provide a schedule of fixtures and other ceiling supported equipment, devices and components and their weights; identify all connection devices and their loading capabilities. B. General 1. Ceiling system classification All buildings within the jurisdiction of the City of Medford are considered as seismic design category D. As such, all suspended ceiling systems that are installed using the provisions of this guide shall be classified as "heavy-duty" ceiling systems as defined by ASTM C 635-00. 2. Limitations and allowances 1
a. General. 1) Use of this guide is limited to buildings with a seismic importance factor (IE ) of 1.00 as determined by Table 1604.5 in the OSSC. Suspended ceiling systems installed in buildings with a seismic importance factor exceeding 1.00 must be engineered. For engineered designs, see Part II of this guide. 2) Ceilings greater than 144 square feet in area with a length to width ratio of 16:1 or greater between ceiling breaks or expansion joints may not use the prescriptive bracing standards specified in this guide. Such systems shall be engineered. For engineered designs see Part II of this guide. 3) Specialty ceilings. Specialty ceilings, must be installed using an engineered design and may not use the provisions of this guide. Specialty ceilings include but are not limited to those: a) Incorporating arched ceilings, curved or curvilinear ceilings or sloped ceilings; or b) Having no direct connection to the surrounding walls, such as "free floating" or "cloud" ceiling elements. 4) Suspended ceilings without panels. Suspended ceilings where no ceiling panels are installed may use the provisions of this guide provided all of the provisions of the guide are incorporated into the design including, but not limited to the requirements for: a) Heavy duty grid; b) Splay wires; c) Lateral bracing; and d) Compression struts. Otherwise, such systems shall be engineered. 5) Suspended ceiling support. Each individual ceiling module must be rigidly supported on two adjacent sides by walls, partitions or soffits. Ceiling designs not meeting this requirement fall out of the scope of this guide and must be engineered. 6) Weight limitation. Suspended ceilings installed according to this prescriptive design shall not exceed 4 pounds per square foot. This weight limitation includes the weight of the grid, panels and any building components or elements including but not limited to light fixtures, mechanical 2
services, electrical or communication or control wiring or cables or insulation. b. Interstitial space. The provisions of this guide apply to suspended ceiling systems that have an interstitial space of 15 feet or less between the suspended ceiling and the supporting structure. c. Grid systems. Suspended ceilings installed to this prescriptive design may use standard grid module systems that are not more than 5 feet in any direction. d. Ceiling panels. 1) Suspended ceilings installed to this prescriptive design may use either standard acoustical lay-in ceiling panels, tegular or kerfed ceiling panels. 2) Specialty ceiling panels such as metal or wood or similar panels may also be used provided the panels: a) Weigh less than 2.75 pounds per square foot; and b) Are retained in the grid by clips or other mechanical fastening devices designed to prevent the panels from dislodging in a seismic event. e. Installation of partitions. Ceilings installed according to this guide shall not support partitions. Partitions may be attached to the grid for cosmetic purposes provided: 1) The partition is supported independently such that the connection between the partition and the ceiling grid does not impose any additional loads on the ceiling grid system; and 2) The connection of the partition to the grid does not cause deflect or rotate more than allowed by other provisions of this guide. C. General Installation Requirements [See Diagram 1] 1. Hanger requirements. a. Hangers shall be located and sized as noted below. All hangers shall be of soft annealed mild steel wire. Hanger location American (measured in both Minimum Diameter Wire Gauge directions) (in inches) number 4 feet on-center 0.080 12 5 feet on-center 0.102 10 3
b. Hangers shall be attached to ceiling suspension members and to supports above with a minimum of three full turns within a 3 inch length. 1) Hangers shall not press against pipes or ducts. Where hangers are sloped they shall comply with the following: a) Wires more than one in six out of plumb shall have counter sloping wires added. b) Counter sloping hangers shall be installed with a minimum 45 degree angle from the horizontal. 2) A trapeze or equivalent shall be used where obstructions prevent direct attachment to the structure. Trapeze suspensions shall be level to within 1/4 inch in 10 feet and shall be a minimum of back to back 1-1/4 inch cold rolled channels when spans exceed 48 inches. 2. Hanger attachments. Hanger attachment devices shall be capable of carrying either 200 pounds or 3 times the ceiling design load as shown by the manufacturer's data or ICC-ES report, whichever is greater. 3. Carrying channels. Carrying channels and main runners shall be level to within 1/4 inch in 10 feet. Leveling shall be performed with hangers taut. Kinks or bends shall not be used to level channels or main runners. Wire loops shall be tightly formed to prevent any vertical movement. 4. Deflection limitations. Deflection from the installation of lighting fixtures or other equipment shall be limited to l/360 times the span between hangers. Where the fixture or equipment causes a deflection in excess of l/360 times the span between hangers, the fixture or equipment shall be independently supported as indicated in Section D. 2 j. A ceiling fixture installation shall n t cause the runners to rotate more than two degrees from the horizontal. D. Seismic Design Requirements 1. General. a. Closure angle. The perimeter supporting closure angle horizontal leg shall be not less than 2 inches. The closure angle supporting the grid wall attachments as noted in b below shall be anchored to the perimeter walls by at least one #6 screw directly attached to the wall framing at not more than 24 inches on-center or by a means approved by BDS staff. [See Diagram 3] b. Grid attachment. One end of the grid shall be attached to the closure angle at each of two adjacent walls. The grid shall be attached by screws, rivets or other approved fasteners. The opposite end of the grid in each horizontal direction shall rest upon the closure angle such that there is ¾ inch clearance between the 4
end of the grid and the wall and the grid is free to slide on the closure angle. [See Diagrams 2, 3 & 4] 2. Lateral Bracing Requirements Lateral bracing shall be provided for suspended ceilings as follows: a. Ceiling height allowance. Ceilings with a maximum of 12 inches between the grid and structural support do not require lateral bracing or compression struts. b. Ceiling area bracing. 1) Ceiling areas less than 144 square feet. Ceiling areas 144 square feet or less in area which are surrounded by walls or soffits which connect directly to the structure above do not require additional lateral bracing. 2) Ceiling areas greater than 144 square feet. a) Ceilings in excess of 144 square feet in area shall be provided with diagonal bracing (splay) wires. Bracing wires shall consist of four0.080 inch (12 gauge) A.W.G. wires connected within 2 inches of an intersection of a main runner with a cross runner, and splayed 90 degrees from each other at an angle not exceeding 45 degrees from the plane of the ceiling. [See Diagrams 1 & 2] (1) Wires are required within 6 feet of any wall and at 12 feet on center in each direction. (2) Where ceilings are 12 feet or less in width, two rows of bracing wires shall be provided. Wires shall be located off-center (less than 6 feet from any wall) and shall be staggered in such a manner that the wires are not directly across from one another. Wires may be located up to 12 feet apart. b) Splay wire alternate. As an alternate to the diagonal splay wires specified above, ceilings may use rigid braces. Braces shall be attached to the grid and to the structure above in a manner to limit lateral deflections at the point of attachment to the ceiling to less than 1/4 inch for the lateral loads expected for the system. c. Perimeter wires. All perimeter wires shall conform to the requirements in Section C, General Installation Requirements, of this guide. In addition, all runners (mains or cross tees) shall be 5
independently supported at the perimeter within 8 inches of the wall or ceiling discontinuity. The wall angle or closure strip shall not be used for this purpose. Perimeter wires may be attached to perimeter walls instead of the structure above provide the wires are positively attached to the wall by using a mechanical fastener such as a drywall screw. The perimeter wire shall be attached to the wall at a slope of not more than 1 horizontal:6 vertical. [See Diagrams 2, 3 & 4] d. Compression struts [See Diagram 1] 1) A strut shall be provided at 12 feet on-center maximum, which shall be fastened to the main runner and shall be extended and fastened to the structure. The structure attachment shall be capable of supporting the dead load of the compression strut. A strut which encapsulates a hanger wire that is attached to the main runner and the structure above need not be separately attached to the runner or the structure above. 2) Based on the maximum spacing of 12 feet on-center in each direction, the following strut sizes and corresponding maximum lengths may be used: 1/2 diameter conduit (EMT) 5-10 3/4 diameter conduit (EMT) 7-8 1 diameter conduit (EMT) 9-9 Single 162S125-33 metal stud 12-0 (1-5/8 x 20 gauge) Back to Back 162S125-33 metal studs 15-0 (1-5/8 x 20 gauge) Single 250S125-33 metal stud 13-6 (2-1/2" x 20 gauge) Max. Length Back to Back 250S125-33 metal studs (2-1/2 x 20 gauge) 15'-0" 6
Where utilizing a strut that is not indicated on the table above, the strut shall be capable of resisting the vertical component of 180 pounds induced by the wires. e. Seismic separation joints required. [See Diagram 7] 1) General. Ceilings with an area greater than 2,500 square feet shall b provided with seismic separation joints. Separation joints shall divide the ceiling area into areas less than 2,500 square feet and shall allow for a minimum of 2 inches of lateral movement of the ceiling providing 1 inch of movement for the portions of ceiling located on either side of the separation joint. Each 2,500 square foot ceiling area shall have its grid attached to a closure angle or other approved device on two adjacent sides as required in section D 1 above. 2) Alternate. In lieu of seismic separation joints, the ceiling may be divided into areas less than 2,500 square feet by the use of partitions or soffits as described below. [See Diagram 6] a) Partitions. Where used, 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. b) Soffits. Where used, soffits shall extend to a point at least level with the plane of the grid and shall be independently supported and braced to the structure above. f. Spacing of bracing members. Lateral force bracing members shall be spaced a minimum of 6 inches from all horizontal piping or duct work that is not provided with horizontal bracing restraints. g. Wire attachment. Wire attachment devices shall be attached to the structure and support a design tension load of at least 200 pounds of pull out. Powder-driven pins shall not be allowed as acceptable attachment devices in concrete construction based on the prohibition of their use by ASCE 9.6.1.6.5. The following table is provided to give guidance for alternates to powder driven pins: Construction Type Fastener Wood 1/4" x 3" screw eyes Steel deck Pre-drop wires, CMI DC1 or DC 2 1/4" metal deck screw eyes 7
Post tension concrete Poured in place concrete Pre-drop wires, embeds, 1/4 x 3/4" metal hit anchors Pre-drop wires, embeds, 1/4 x 3/4" metal hit anchors h. Stabilizing members. Members perpendicular to the wall at the unattached sides of the grid shall be tied together (stabilized) to prevent their spreading. Members shall be tied together at a point not more than 8 inches from and parallel to the wall. [See Diagrams 2 & 4] i. Ceiling mounted light fixtures, egress lights, speakers, air terminals and mechanical services. [See Diagram 8] Lighting fixtures, egress lighting, speakers, air terminals or mechanical services weighing up to 56 pounds and directly supported by the ceiling grid system shall be positively attached to the ceiling system. Attachment shall be made with a minimum of 4 approved fasteners located within 3 inches of the grid intersections to suspension main runners, or to cross runners with the same carrying capacity as the main runners. In addition to the above grid connection fixtures weighing 20 pounds but not more than 56 pounds, shall have two 0.080 inch (12 gauge A.W.G) hangers connected from the fixture to the ceiling system hangers or to the structure above. These wires may be slack. Fixtures weighing less than 20 pounds do not require slack wires. [See Diagram 10] Fixtures weighing more than 56 pounds shall be supported independently from the grid system directly from the structure above by approved hangers. j. Ceiling penetrations. Sprinkler heads or other similar ceiling penetrations shall be provided with at least one inch of clearance in all directions surrounding the sprinkler head or extension. The opening shall allow for at least 1 inch of lateral movement by the ceiling, in any horizontal direction, without causing damage to the sprinkler head or extension. Where either of the following alternates is used, the opening surrounding the penetration may be reduced to 1/4 inch. 1) Where rigid braces as described in Ceiling area bracing, splay wire alternate above (I D 2 b 2) b)) are used or, 2) If the sprinkler head or other penetration is provided with a listed flexible connector capable of accommodating 1 inch of 8
ceiling movement in all horizontal directions without harming the sprinkler head or other protrusion. [See Diagram 9] k. Cable trays, electrical conduit, communication cable and other similar installations shall be supported independently from the ceiling. 3. Special Inspection. Special inspections will not be required for suspended ceiling systems installed in compliance with all of the prescriptive standards specified in this guide. II. NEW SUSPENDED CEILINGS - ENGINEERED DESIGN A. General An "engineered design" for a suspended ceiling shall be designed and certified by an architect or engineer, registered in the State of Oregon. Engineered systems shall include support of lighting, mechanical systems or partitions. B. Permit Application The permit application for a suspended ceiling to be installed according to an engineered design shall include three copies of certified drawings and specifications, and one copy of calculations, prepared by an architect or engineer registered in the State of Oregon. The submittal shall show that the ceiling system's capacity to resist vertical loads and seismic loads in compliance with applicable code chapters and standards; shall identify whether the suspension is light, intermediate, or heavy duty; and shall identify all connection devices and their allowable capacities. The submittal shall include appropriate substantiating data, manufacturer's data and ICC-ES Evaluation Reports. III. Upgrading of Existing Ceilings A. Ceilings without Seismic Bracing Where existing ceilings are without seismic bracing, the ceiling system shall be brought into substantial compliance with current code requirements (including compression struts at the center of the splayed wires, attachment of slack wires from light fixtures and air terminals to the structure, etc.) when a substantial amount (50% or more) of the ceiling tile is removed, altered or repaired as part of a general space alteration, or if all the ceiling is removed for washing, painting or replacement. This requirement does not trigger the need for a closure angle as required above in part I D 1 of this guide. These upgrades are not required when: 9
1. Removing portions of tiles or panels and/or grid to alter ductwork, sprinkler pipe, etc. 2. Lateral bracing and fixture attachment will not be required when portions of a ceiling are removed only to facilitate the installation of sprinkler piping. B. Ceilings without Compression Struts Where existing ceilings have seismic bracing but do not have compression struts at the center of the splayed wires, the addition of compression struts will only be required when and where the grid is replaced, altered, raised or lowered. Attachments: The diagrams included with this guide are intended to help clarify for the user some of the requirements specified in the guide. These diagrams are not design or construction documents and are intended only to illustrate some of the technical aspects of the guide. 10
Diagram 1: General Installation Requirements 11
Diagram 2: Typical Ceiling Grid Layout 12
Diagram 3: Unattached End of Grid Diagram 4: Attached End of Grid 13
Diagram 5: Perimeter Wires & Stabilizer Bar 14
Diagram 6: Soffit Detail Diagram 7: Seismic Separation Joint 15
Diagram 8: Fixture Support 16
Diagram 9: Alternate Sprinkler Penetration Diagram 10: Light Fixture Less Than 20 Pounds 17