Safety, code issues of drop-out ceilings

Drop-out ceilings should have an evaluation report, and designers should discuss their use with the authority having jurisdiction during design and specification.


Figure 4: Drop-out panels are used areas requiring high levels of hygiene, such as this quality control lab. Pipes, sprinklers, light fixtures, and other services are located above the ceiling to minimize dirt-collecting surfaces. Equally important, the tDrop-out ceilings should have an evaluation report from an independent listing agency-such as the International Association of Plumbing and Mechanical Officials' Uniform Evaluation Service (IAPMO-UES), FM Global, UL, or CertMark International-that is acceptable to the authority having jurisdiction (AHJ). Because some individuals are unfamiliar with drop-out ceilings, designers should discuss their use with the AHJ while the project is still in design.

Thermoformed ceiling panels should be Class A-rated (flame spread <25 and smoke developed <450) according to ASTM E84: Standard Test Method for Surface Burning Characteristics of Building Materials, and V0-Rated (self-extinguishing) when tested according to UL 94: Flame Rating. The ceiling assembly should be tested according to Uniform Building Code (UBC) Standard 26-3 Room Fire Test Standard for Interior of Foam Plastic Systemsas modified according to appropriate acceptance criteria.

Approved drop-out panels are currently available that have been evaluated for use in areas classified under NFPA 13: Standard for the Installation of Sprinkler Systems as light hazard and ordinary hazard, Group 1. These are occupancies in which combustibility or quantity of contents is low to moderate and fires with low or moderate heat release are expected.

All drop-out panels currently available have been evaluated for use with standard-response (SR) sprinklers. One drop-out panel has been recently listed for use with quick-response (QR) sprinklers (see IAPMO Evaluation Report No. 0310). This is a significant development, as QR sprinklers are required in light-hazard occupancies.

Evaluation reports specify allowable sprinkler heights above the ceiling panels and require identification of the report on product packaging. For example, a 0.013-in.-thick vinyl drop-out panel used with QR sprinklers rated at 155°F or higher requires sprinklers be installed 1 in. or less from the top of the ceiling grid. And SR sprinklers rated 165°F or higher can be installed from 1 to 60 in. above the ceiling panels. Sprinklers must be installed in compliance with all of the NFPA 13 or NFPA 13R requirements.

Depending on a product's approval listing:

  • To avoid possible trip hazards to firefighters, drop-out panels are prohibited in defined exit corridors, stairways, horizontal exits, pressurized enclosures, and exit passageways. They are not a trip hazard to room occupants because they drop at an elevated temperature, by which time occupants should be out of the room. Even if a person comes into contact with a panel, drop-out panels are very lightweight and unlikely to injure.
  • While fibrous acoustical insulation is not permitted between ceiling panels and sprinklers, there is an approved thermoformed backer pan that improves a ceiling's noise-reduction coefficient and thermal insulating properties. The backer also helps diffuse over-ceiling light sources and reduces the shadows of detritus that might accumulate on top of panels.
  • Drop-out panels do not provide the concealment required with soft-soldered copper pipe or combustible plastic pipe.
  • While no drop-out ceiling is approved as part of a fire-resistance-rated assembly, drop-out ceilings can be installed below a rated assembly.
  • The space above drop-out panels should not be used as an air plenum. Panels may not be installed with clips that prevent downward movement.
  • Uplift-prevention clips are permitted but not required.
  • Where it is necessary to extend a sprinkler through a drop-out ceiling, the hole through the ceiling should be oversized to assure that falling panels do not get hung up on the sprinkler.

Ed Davis is president of Ceilume, a unit of Empire West Inc., and headed the research program that led to an IAPMO-UES listing for the company's drop-out ceilings. Michael Chusid is an architect working to develop innovative building products that improve industry best practices.

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