Suspended Acoustical Ceilings

Summary

Suspended acoustical ceilings are panels or tiles that drop into a metal suspension grid hung from the structure, hiding services above and absorbing sound. Grid duty class, seismic bracing, panel absorption and sound-blocking ratings, and fire classification all follow from the project's seismic category and room use.

Cols

Image

ASTM C635: manufacture, performance, and testing of metal suspension systems for acoustical tile and lay-in panel ceilings
ASTM C636: installation of metal ceiling suspension systems
ASTM E580: installation of ceiling systems in seismic areas
ASTM E1264: classification of acoustical ceiling products by type, pattern, and ratings
Main runner and cross tee: primary and secondary members of the grid
NRC (noise reduction coefficient): sound absorption within the room
CAC (ceiling attenuation class): sound blocked between rooms over a shared plenum
LR (light reflectance): fraction of light the panel face reflects

Standards

Grid duty classes (ASTM C635)

Light duty: minimal ceiling loads; one manufacturer lists about 5 lb per linear foot
Intermediate duty: moderate extra loads such as light fixtures; about 12 lb per linear foot
Heavy duty: heavier fixtures and equipment; about 16 lb per linear foot
One manufacturer guide states heavy duty is required for Seismic Design Categories D to F and intermediate duty for C

Panels (ASTM E1264)

Type III is a mineral-base panel with a painted finish; Form 2 is the water-felted version
Pattern C is perforated with small holes
Common size 24 by 24 in., about 3/4 in. thick
Fire performance reported as Class A
Light reflectance of 0.83 or higher is a high-reflectance category

Detailing

Hang 12-gauge wire at 4 ft on center along main runners, and at perimeter ends within about 8 in. of walls
Seismic areas: use 2 in. wall molding in Seismic Design Category D to F and 7/8 in. in C, with 3/4 in. clearance at free walls
Ceilings over 1,000 sq ft need horizontal restraint wires or rigid bracing; over 2,500 sq ft need seismic separation joints or full-height partitions
Coordinate lights, diffusers, sprinklers, and access with grid layout
Install fire-resistance-rated ceilings as in the tested assembly

Uses

Specific uses

Offices, schools, and healthcare rooms
Corridors and retail spaces
Spaces needing access to ducts and wiring above
Rooms needing sound absorption

Pros and cons

Pros

Hides and gives access to services above
Absorbs sound and reflects light
Easy to replace panels and change layout

Cons

Plenum paths let sound pass between rooms unless the CAC is high
Seismic bracing adds cost and layout limits

Manufacturing and cost

Construction

A grid of main runners and cross tees is hung on wire from the structure and edged with wall molding
Panels are laid into the grid and cut at the perimeter

Main manufacturers and suppliers

Trade association: Ceilings & Interior Systems Construction Association (CISCA).

Sources

Armstrong: seismic design, what you need to know, https://www.armstrongceilings.com/content/dam/armstrongceilings/commercial/north-america/brochures/seismic-design-what-you-need-to-know-brochure.pdf
Armstrong: installation requirements for suspended ceilings, https://www.armstrongceilings.com/commercial/en/performance/ceilings-for-seismic-design/installation-requirements.html
USG: seismic technical guide, light duty suspension systems, https://www.usg.com/content/dam/USG_Marketing_Communications/united_states/product_promotional_materials/finished_assets/seismic-technical-guide-light-duty-suspension-systems-en-SC2499.pdf
ASTM International: E1264 standard classification for acoustical ceiling products, https://www.document-center.com/standards/show/ASTM-E1264
Unified Facilities Guide Specifications: 09 51 00 acoustical ceilings, https://www.wbdg.org/FFC/DOD/UFGS/UFGS 09 51 00.pdf
California Division of the State Architect: IR 25-2, https://www.dgs.ca.gov/-/media/Divisions/DSA/Publications/interpretations_of_regs/IR_25-2.pdf