The 1935 Miami Dade Building Code establishes a hierarchy of five construction type classifications to regulate building safety based on fire resistance and material composition. This system ranges from Type I, the most fire-resistive, to Type V, the least fire-resistive 1935-Miami-Dade-Building-Code_p105_124. The classification determines allowable height, area, and specific construction requirements for structural frames, walls, floors, and roofs.
Classification Hierarchy
The code defines the following types 1935-Miami-Dade-Building-Code_p105_124:
- Type I (Fire-Resistive): The highest level of fire resistance. Structural frames must be of fireproofed structural steel/iron or reinforced concrete. Exterior walls, foundations, and inner court walls must be masonry or reinforced concrete. There are no limits on height or floor area for this type 1935-Miami-Dade-Building-Code_p105_124.
- Type II (Heavy Timber): Allows for structural frames of fireproofed steel/iron, reinforced concrete, masonry, or heavy timbers. Height is generally limited to 75 feet (7 stories), with specific allowances for sloping ground 1935-Miami-Dade-Building-Code_p105_124.
- Type III (Ordinary Masonry): Requires masonry or reinforced concrete for foundations and exterior walls, while interior load-bearing construction may be masonry, concrete, steel, or wood. Height is limited to 55 feet (5 stories) 1935-Miami-Dade-Building-Code_p105_124. Wood construction is permitted but cannot pass through exterior walls, and cornices must be incombustible 1935-Miami-Dade-Building-Code_p125_144.
- Type IV (Metal Frame Construction): Defined as structures with steel, iron, masonry, or reinforced concrete frameworks and metal or other incombustible exterior walls and roofs 1935-Miami-Dade-Building-Code_p125_144. Height is limited to 45 feet (55 feet on sloping ground) with a maximum of one story and a mezzanine 1935-Miami-Dade-Building-Code_p125_144. Interior partitions must be of metal or other incombustible materials, and fireproofing of structural members is not required 1935-Miami-Dade-Building-Code_p125_144.
- Type V (Wood Frame Construction): The least fire-resistive type, encompassing all wood-frame buildings not classified as Types I-IV 1935-Miami-Dade-Building-Code_p125_144. Height is limited to 38 feet (two stories) or 45 feet on sloping ground 1935-Miami-Dade-Building-Code_p125_144. Specific restrictions apply, particularly in fire-zones, where Type V buildings may be prohibited or subject to strict alteration rules 1935-Miami-Dade-Building-Code_p105_124.
Key Requirements by Type
Structural Integrity and Fireproofing
For construction-type-classifications I and II, the code mandates rigorous fireproofing of structural members. Type I buildings require 3-4 hours of fire-resistive protection for columns, beams, and girders, depending on the building’s height 1935-Miami-Dade-Building-Code_p105_124. Type II buildings require similar protection for steel and concrete members, but wood structural members are exempt from fireproofing requirements due to their inherent mass and charring properties 1935-Miami-Dade-Building-Code_p105_124. In contrast, Type IV buildings do not require fireproofing of structural members 1935-Miami-Dade-Building-Code_p125_144.
Exterior Walls and Openings
All types require robust exterior walls. Type I and II buildings must have exterior walls of masonry or reinforced concrete with at least four-hour fire-resistive construction 1935-Miami-Dade-Building-Code_p105_124. Openings in these walls, such as doors and windows, generally require one-hour fire-resistive protection, with exceptions for openings facing wide public streets 1935-Miami-Dade-Building-Code_p105_124.
Type IV buildings require exterior walls of galvanized iron (not less than 22 gauge) or other approved non-corrosive metal, attached to horizontal incombustible supports no more than three feet apart 1935-Miami-Dade-Building-Code_p125_144. Openings in Type IV exterior walls must be protected by metal doors/windows unless set back 16 feet from property lines 1935-Miami-Dade-Building-Code_p125_144.
Type V buildings require exterior walls constructed with 2x4 studs at 16-inch centers or 4x4 posts at 5-foot centers 1935-Miami-Dade-Building-Code_p125_144. Exterior walls must be covered with weatherboarding, shingles, stucco, masonry veneer, or galvanized metal 1935-Miami-Dade-Building-Code_p125_144. Weatherboarding must average 5/8-inch thickness 1935-Miami-Dade-Building-Code_p125_144. Stucco requires metal lath reinforcement and two coats totaling 7/8-inch thickness 1935-Miami-Dade-Building-Code_p125_144.
Vertical Openings and Egress
Enclosures for vertical openings like stairwells and elevator shafts are critical for fire-separation-standards. Type I and II buildings require two-hour fire-resistive enclosures for these shafts 1935-Miami-Dade-Building-Code_p105_124. Type III buildings require one-hour fire-resistive enclosures 1935-Miami-Dade-Building-Code_p105_124. These requirements support broader egress-and-exit-standards by preventing smoke and fire spread through vertical channels.
For Type IV buildings, there are no restrictions on the enclosure of vertical openings 1935-Miami-Dade-Building-Code_p125_144. For Type V buildings (except dwellings under Group I Occupancy), enclosure walls for elevator shafts, vent shafts, and stairwells must be not less than one-hour fire-resistive construction 1935-Miami-Dade-Building-Code_p125_144. Openings into these enclosures must be closed with solid slab wood doors not less than 1 3/8 inches thick or equivalent, hinged to be gravity self-closing 1935-Miami-Dade-Building-Code_p125_144.
Fire Stopping and Combustible Materials
Type III buildings restrict wood from passing through exterior walls and limit vertical wood framing air spaces to seven feet 1935-Miami-Dade-Building-Code_p125_144. Type V buildings require effective fire stopping at floors and ceilings to limit concealed air spaces to seven feet 1935-Miami-Dade-Building-Code_p125_144. Combustible insulating materials may be used in partitions, floors, or roofs but must not interfere with required fire blocking 1935-Miami-Dade-Building-Code_p125_144.
Interaction with Fire Zones
The construction-type-classifications interact directly with fire-zones. For instance, in fire-zones No. 1, buildings of Type IV and V construction over 400 square feet are heavily restricted, often requiring demolition or relocation if altered significantly 1935-Miami-Dade-Building-Code_p105_124. Similarly, Type IV buildings over 1,000 square feet are prohibited in fire-zones No. 2 1935-Miami-Dade-Building-Code_p105_124. This integration ensures that higher-risk construction types are not permitted in areas with higher fire hazards.
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