Structural Fire Protection Tables
The 1935 Miami Dade Building Code provides detailed tabulations specifying the minimum thickness of incombustible insulating materials required to protect structural components for specific fire-resistive periods (1, 2, 3, and 4 hours) 1935-Miami-Dade-Building-Code_p285_304 (p. 285). These tables are central to the structural-fire-protection-tables and ensure that structural-steel-design and reinforced-concrete-design meet safety standards by preventing structural failure during a fire.
Protection of Steel and Cast Iron
For steel or cast iron columns, projecting beam flanges, and primary truss members, the code mandates specific insulation thicknesses depending on the material used 1935-Miami-Dade-Building-Code_p285_304 (p. 285). Common materials include:
- Concrete: Distinguished between Grade A (low siliceous content) and Grade B concrete 1935-Miami-Dade-Building-Code_p285_304 (p. 286).
- Gunite: Sprayed concrete application.
- Masonry: Brick of clay, shale, concrete, or sand-lime.
- Gypsum: Solid or hollow blocks, and poured gypsum.
- Plaster: Metal lath and gypsum or Portland cement plaster, often requiring air spaces for higher ratings 1935-Miami-Dade-Building-Code_p285_304 (p. 285).
Similar tables apply to the webs of steel beams and girders, with slightly reduced thickness requirements compared to columns for certain materials 1935-Miami-Dade-Building-Code_p285_304 (p. 285).
Reinforcement Protection
The tables also specify cover depths for reinforcing steel in reinforced-concrete-design components:
- Columns, Beams, and Trusses: Minimum cover varies by concrete grade and required fire resistance 1935-Miami-Dade-Building-Code_p285_304 (p. 285).
- Joists: Slightly reduced cover requirements compared to primary members 1935-Miami-Dade-Building-Code_p285_304 (p. 285).
- Floor and Roof Slabs: Protection for reinforcing and tie rods is specified for both concrete and gypsum materials 1935-Miami-Dade-Building-Code_p285_304 (p. 285).
Ceiling and Joist Protection
Ceiling protection for roof and secondary trusses is detailed, allowing for metal lath, plaster, concrete, or gunite 1935-Miami-Dade-Building-Code_p285_304 (p. 285). For suspended ceilings with a free air space of at least 1 inch, protection thicknesses may be reduced by ½ inch, with a minimum of ¾ inch 1935-Miami-Dade-Building-Code_p285_304 (p. 286, 291).
Specific tables for floor-construction-standards address metal and wood joists:
- Steel Joists: Protected by ceiling materials like plaster or gunite, assuming an incombustible slab above 1935-Miami-Dade-Building-Code_p285_304 (p. 292).
- Wood Joists: Protected by plaster ceilings, with specific requirements for double wood floors 1935-Miami-Dade-Building-Code_p285_304 (p. 292).
Material Specifications
The code defines material grades to ensure consistency in fire protection:
- Grade A Concrete: Contains aggregates with not more than 65% siliceous material 1935-Miami-Dade-Building-Code_p285_304 (p. 286).
- Grade B Concrete: Contains other coarse aggregates; unknown aggregates default to Grade B 1935-Miami-Dade-Building-Code_p285_304 (p. 286, 287).
- Plaster Reinforcement: Plaster over 1 inch thick requires embedded galvanized metal lath or wire mesh 1935-Miami-Dade-Building-Code_p285_304 (p. 286). Gypsum plaster board may substitute for lath in specific conditions 1935-Miami-Dade-Building-Code_p285_304 (p. 287).
These tables are integral to fire-resistive-construction-requirements, ensuring that structural integrity is maintained during fire events.