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Specification Guide

Ceiling Grid Specifications: T-Bar Sizes, Load Ratings & Profiles

Everything you need to know about suspended ceiling grid systems — from an installer's perspective.

The grid is the skeleton of a suspended ceiling. Get it wrong and you've got sagging tiles, misaligned light fixtures, and a ceiling that won't pass inspection. This guide covers the standard grid specifications that architects, general contractors, and facility managers need to know when specifying or evaluating a suspended acoustical ceiling system.

Grid Face Widths

The face width is the visible part of the grid tee when you look up at the ceiling. It's the single biggest aesthetic decision in a grid ceiling.

  • 15/16" (24mm) — Standard: The workhorse. Most commercial ceilings use 15/16" face grid. It's strong, widely available, and works with every tile on the market. Good for offices, schools, healthcare, government — anywhere function matters more than a designer look.
  • 9/16" (15mm) — Narrow Face: A thinner profile that shows less grid and more tile. Popular in Class A offices, medical offices, and retail where a cleaner look is worth the cost premium. Costs roughly 15-20% more than 15/16". Requires compatible tiles — not every tile works with narrow-face grid.
  • Concealed / Slot: The grid is hidden behind the tile edges. Only the slot between tiles is visible — a thin shadow line. Used in high-end offices, lobbies, and anywhere that wants a monolithic ceiling look. Higher cost, more labor-intensive to install, and not all tiles are compatible.

Grid Module Sizes

The module size is the tile opening — how big each grid cell is.

  • 2' × 2' (600mm × 600mm): The most common layout in California. Looks better than 2×4 because the grid pattern is more proportional. More cross tees per square foot, so slightly more labor and material cost. Most 2×2 tiles are tegular or reveal edge.
  • 2' × 4' (600mm × 1200mm): The budget option. Fewer cross tees means faster installation and lower material cost. Common in back-of-house areas, warehouses, and budget-conscious projects. Most 2×4 tiles are lay-in with a flat or angled edge.

Use our Ceiling Grid Calculator to figure out exactly how many main tees, cross tees, wall angles, and hanger wires your project needs for either layout.

Grid Components

A suspended grid system has four main components:

  • Main Tees (Main Runners): The primary structural members that run the length of the room. Typically 12' long, spliced end-to-end for longer runs. Suspended from the structure above by hanger wires at 4' on center (max). Main tees carry the load.
  • Cross Tees: Shorter members that connect between main tees. 2' cross tees create the grid cells. In a 2×2 layout, you have 2' cross tees at 2' on center. In a 2×4 layout, you have 4' cross tees at 2' on center with optional 2' intermediate tees.
  • Wall Angle (Wall Molding): An L-shaped channel that runs around the perimeter of the room. The grid tees rest on the wall angle at the edges. Standard is 7/8" face; hemmed edge looks cleaner than raw cut.
  • Hanger Wire: 12-gauge galvanized wire that connects the main tee to the structure above. Attached to the structure with concrete anchors, beam clamps, or eye lag screws depending on the substrate. Maximum spacing: 4' on center along the main tee, with the first wire within 2' of each wall.

Load Ratings

Grid systems are rated by the weight they can carry per linear foot of main tee. This matters when you're adding heavy light fixtures, HVAC diffusers, or specialty panels.

  • Standard Duty: Supports standard mineral fiber or fiberglass tiles (typically 0.5-1.5 lbs/SF). Adequate for most office and commercial applications.
  • Intermediate Duty: Supports heavier tiles plus moderate fixture loads. Good for metal ceiling panels and rooms with many light fixtures.
  • Heavy Duty: Supports up to 56 lbs per linear foot. Required for wood plank ceilings, heavy metal panels, and applications with significant above-ceiling equipment attached to the grid.

Armstrong, USG, and Chicago Metallic all publish load tables for their grid systems. The load rating needs to account for tile weight, fixture weight, and seismic forces in California.

Seismic Requirements (California)

Every suspended ceiling in California needs seismic bracing per the California Building Code (CBC), which adopts ASCE 7 with California amendments. The basic requirements:

  • Compression struts or bracing wires: At 12' on center (max) in both directions, plus within 2' of each wall
  • Perimeter clips: Grid tees are clipped to the wall angle to prevent uplift during a seismic event
  • Pop rivets: Cross tee connections to main tees are riveted — they can't rely on friction alone
  • Hold-down clips: Tiles in healthcare and other critical occupancies get hold-down clips to prevent them from falling during shaking

For the full breakdown of California seismic requirements, see our Seismic Ceiling Requirements Guide.

Major Grid Manufacturers

  • Armstrong Prelude: The most widely specified grid in commercial construction. Available in standard, XL (heavy duty), and DGS (Drywall Grid System) profiles. Compatible with all Armstrong tiles and most other manufacturers' tiles.
  • USG Donn: The original T-bar grid system. DX/DXL main tees, Centricitee cross tees. Extremely durable — a lot of the 30-year-old grids we pull out in renovations are USG Donn that's still in good condition.
  • Chicago Metallic: Owned by Rockfon. Makes both standard exposed grid and concealed/bandraster systems for high-end applications. Their 200 Series snap-in grid is popular for metal ceiling installations.

Specifying Grid: What to Include

If you're an architect or spec writer, here's what belongs in Division 09 51 00 (Acoustical Ceilings) for the grid:

  • Face width (15/16" or 9/16")
  • Module size (2×2 or 2×4)
  • Tee profile (flat, stepped, tegular-compatible)
  • Load rating (standard, intermediate, heavy duty)
  • Finish (painted white, black, chrome, custom color)
  • Seismic category and bracing requirements per CBC/ASCE 7
  • Fire-rated assembly (if applicable — see Fire Rating Guide)

Questions?

If you're specifying a grid system and want an installer's input on what works best, give us a call. We've installed millions of linear feet of grid and we know what holds up, what doesn't, and where the value is in each manufacturer's lineup.