Type X vs. Type C GWB

Study Guide: CGC Type X vs. Type C Gypsum Boards

This video highlights the critical differences between Type X and Type C gypsum boards, debunking the misconception that they are interchangeable. The primary focus is on their fire-performance capabilities and appropriate applications in construction.

1. Key Misconceptions (0:30-0:51)

  • Myth: There are only two basic types of board: regular and Type X.

  • Myth: All gypsum board products of the same type are identical, regardless of manufacturer.

  • Fact: Years of laboratory testing show significant differences in fire performance between manufacturers and between types of panels.

2. Type X Gypsum Board

  • Definition/History: Introduced by CGC in the 1950s (Sheetrock Brand Firecode X) (0:59-1:02).

  • Core Construction: Contains special glass fibers and other additives to reinforce the core (1:10).

  • Performance: Maintains structural integrity while the core shrinks from thermal exposure (1:15).

  • Best Application: Designed to provide 1-hour fire ratings for wall assemblies (1:05).

3. Type C Gypsum Board

  • Definition/History: Introduced in the early 1960s (Sheetrock Brand Firecode C) as construction practices changed to include lighter gauge steel and taller buildings (1:25-1:40).

  • Core Construction: Features a special core formulation that provides even greater fire resistance than Type X (1:45).

  • Performance: Advanced formulation compensates for shrinkage during fire exposure, preventing premature collapse (2:55).

  • Best Application: The standard for floor-ceiling assemblies (1:57).

4. Bench Burn Test Comparison (2:12-3:02)

  • Purpose: To illustrate product differences, not specifically to measure absolute fire resistance times.

  • Test Setup: A loaded sample of 5/8-inch gypsum board is exposed to a gas-fired burner (2:25-2:31).

  • Result at 57 minutes: The Type X panel collapses from heat, while the Type C panel remains unaffected (2:38-2:41).

  • Result at 2 hours: The Type C panel has still not collapsed (2:50-2:55).

5. Summary: When to Use Which? (3:05-3:20)

  • Use Type X: For most wall applications.

  • Use Type C: Crucial for single-layer fire-rated ceiling assemblies, especially when insulation is placed in the plenum.