Building Construction

6 Objectives Describe the characteristics of building materials: masonry, concrete, steel, glass, gypsum board, and wood. List the characteristics of each type of building construction: fire-resistive construction, noncombustible construction, ordinary construction, heavy timber construction, and wood-frame construction. Describe how each of the five types of building construction react to fire. Describe the function of each of the following building components: foundations, floors, ceilings, roofs, trusses, walls, doors, windows, interior finishes, and floor coverings.

Introduction Knowing building construction enables fire fighters to: 6 Introduction Knowing building construction enables fire fighters to: Predict how a fire will spread Make determinations about structural integrity Recognize warning signs of imminent collapse Fire risks also depend on occupancy and contents. Occupancy: how a building is used Contents: vary, but usually related to building use

Construction Material Properties and Fire Behavior 6 Construction Material Properties and Fire Behavior Key factors affecting combustibility: Combustibility Thermal conductivity Loss of strength when heated Rate of thermal expansion

Types of Construction Materials 6 Types of Construction Materials Masonry Concrete Steel and other metals Glass Gypsum board Wood Plastics

Masonry 6 Inherently fire-resistive Poor conductor of heat Openings can allow fire to spread. With prolonged exposure to fire, masonry can collapse.

Concrete Inherently fire-resistive Poor conductor of heat 6 Concrete Inherently fire-resistive Poor conductor of heat Strong under compression Weak under tension Can be damaged through exposure to fire Spalling

Steel 6 Strongest material in common use Strong in both compression and tension Will rust if exposed to air and moisture Not fire-resistive Good conductor of heat Expands and loses strength when heated Any sign of bending, sagging, or stretching indicates immediate risk of failure.

Other Metals Aluminum Copper Zinc Often melts and drips in fires 6 Other Metals Aluminum Often melts and drips in fires Copper Primarily used for piping and wiring Zinc Primarily used as a protective coating for metals

Glass Noncombustible, but not fire-resistive 6 Glass Noncombustible, but not fire-resistive Ordinary (non-treated) glass will break when exposed to flame.

Gypsum Board Not a strong structural material 6 Gypsum Board Not a strong structural material Used mainly for finishing Very good insulator Limited combustibility Paper will burn, but gypsum itself will not. Often used as a firestop Prolonged exposure to fire will cause failure. Moisture in the material will evaporate causing deterioration.

Wood Most common building material Highly combustible 6 Wood Most common building material Highly combustible Weakens when heated Fire-retardant chemicals can weaken wood.

Plastics Rarely used for structural support Combustibility varies 6 Plastics Rarely used for structural support Combustibility varies Many plastics release dense, toxic smoke when they burn. Thermoplastic materials melt and drip. Thermoset materials lose strength but will not melt.

Construction Type Determination 6 Construction Type Determination Classification based on combustibility and fire resistance Codes specify construction type required based on: Height Area Occupancy Location

Types of Construction Type I: Fire-Resistive Type II: Noncombustible 6 Types of Construction Type I: Fire-Resistive Type II: Noncombustible Type III: Ordinary Type IV: Heavy Timber Type V: Wood Frame

Type I: Fire-Resistive 6 Type I: Fire-Resistive All structural components must be noncombustible. Used for: Large numbers of people Tall or large area Special occupancies Building materials should not provide fuel for a fire. Contents may burn but the building should not. Steel framing must be protected. Fires can be very hot and hard to ventilate. In extreme conditions Type I buildings can collapse.

Type II: Noncombustible 6 Type II: Noncombustible All structural components must be noncombustible. Fire-resistive requirements are less stringent than Type I. Structural components contribute little or no fuel. Fire severity is determined by contents. Most common in single-story warehouses or factories

Type III: Ordinary 6 Used in a wide range of buildings Masonry exterior walls support floors and roof. Usually limited to no more than four stories Limited fire resistance requirements Two separate fire loads: Construction materials Contents Fire resistance depends on building age and local building codes. Exterior walls, floors, and roof are connected.

Type IV: Heavy Timber 6 Exterior masonry walls Interior structural elements, floors, and roof of wood No concealed spaces or voids Used for buildings as tall as eight stories Open spaces suitable for manufacturing and storage New Type IV construction is rare.

Type V: Wood Frame (1 of 2) 6 Most common type of construction in use All major components are wood or other combustible materials. Can rapidly become fully involved Collapse frequently Used in buildings of up to four stories Wooden I-beams and trusses Just strong enough to carry required load No built-in safety margin Collapse early and suddenly

Type V: Wood Frame (2 of 2) 6 Balloon-frame construction Exterior walls assembled with continuous wood studs from the basement to the roof. Platform-frame construction Exterior wall studs not continuous.

Building Components Foundation Floors and ceilings Roofs Trusses Walls 6 Building Components Foundation Floors and ceilings Roofs Trusses Walls Doors and windows Interior finishes and floor coverings

Foundation Ensures building is firmly planted 6 Foundation Ensures building is firmly planted Helps keep all other components connected Weak or shifting foundations can cause collapse.

Floors and Ceilings 6 Fire-Resistive Floors Wood-Supported Floors Floor-ceiling system designed to prevent vertical fire spread If space above ceiling is not partitioned or sprinklered, fire can quickly extend horizontally across a large area. Wood-Supported Floors Heavy-timber floors can often contain a fire for an hour or more. Conventional wood flooring burns readily and can fail in as little as 20 minutes. Modern, lightweight wood I-beams and trusses Little fire resistance

Roofs Not designed to be as strong as floors Three primary designs: 6 Roofs Not designed to be as strong as floors Three primary designs: Pitched roofs Curved roofs Flat roofs

Pitched Roofs Sloped or inclined 6 Pitched Roofs Sloped or inclined Can be gable, hip, mansard, gambrel, or lean-to Usually supported by rafters or trusses Require some sort of roof covering

6 Curved Roofs Used for large buildings that require large, open interiors Supermarkets Warehouses Industrial buildings Usually supported by bowstring trusses or arches

6 Flat Roofs (1 of 2) Usually found on houses, apartment buildings, warehouses, factories, schools, and hospitals Have a slight slope for drainage Wood support structures use solid wood beams and joists.

6 Flat Roofs (2 of 2) Lightweight construction techniques employ wood I-beams and trusses. Open-web steel trusses (bar joists) often used for support Most coverings highly combustible Ventilation may involve cutting through many layers of roofing.

Trusses 6 Triangular geometry creates a strong, rigid structure. Usually prefabricated wood or steel Three types: Parallel chord Used for flat roofs and floors Pitched chord Used for pitched roofs Bowstring Used for curved roofs

Walls Most visible part of a building 6 Walls Most visible part of a building Constructed of a variety of materials Walls are: Load-bearing Nonbearing Specialized

Load-Bearing Walls Give structural support Either interior or exterior 6 Load-Bearing Walls Give structural support Either interior or exterior Support both “dead load” and “live load” Damaged wall can result in collapse

Nonbearing Walls Support only their own weight 6 Nonbearing Walls Support only their own weight Can be breached or removed without compromising structural integrity Either interior or exterior

Specialized Walls (1 of 2) 6 Specialized Walls (1 of 2) Party walls Common to two properties Almost always load-bearing Often a fire wall Fire walls Designed to limit horizontal fire spread Extend from foundation through roof Constructed of fire-resistant materials

Specialized Walls (2 of 2) 6 Specialized Walls (2 of 2) Fire partitions Interior walls that extend from a floor to underside of floor above Fire enclosures Fire-rated assemblies that enclose vertical openings Curtain walls Nonbearing exterior walls attached to the outside of a building

Walls Solid, load-bearing masonry walls can reach six stories high. 6 Walls Solid, load-bearing masonry walls can reach six stories high. Nonbearing masonry walls can reach almost any height. Never assume that exterior walls are masonry.

Doors Can be used for entry, exit, light, and ventilation 6 Doors Can be used for entry, exit, light, and ventilation Mostly constructed of wood or metal Hollow-core wood doors offer little fire resistance. Solid-core doors provide some fire resistance. Metal doors more durable and fire-resistant.

Window Assemblies Used for light, ventilation, entry, and exit 6 Window Assemblies Used for light, ventilation, entry, and exit Window type depends on a variety of factors.

Fire Doors and Fire Windows 6 Fire Doors and Fire Windows Constructed to prevent spread of flames, heat, and smoke Must meet NFPA 80 Labeled according to approved-use Class A Class B Class C Class D Class E Fire windows are used when a window is needed in a required fire-resistant wall.

Interior Finishes and Floor Coverings 6 Interior Finishes and Floor Coverings Finishes and coverings are exposed interior surfaces of a building. Different interior finish materials contribute in various ways to a building fire.

Construction or Demolition 6 Construction or Demolition Construction or demolition sites pose special problems for fire fighters. Built-in fire protection features are often missing. Fire-resistive enclosures can be missing. Often unoccupied for long periods

6 Summary Many materials are used in building construction, and each material reacts differently to heat and fire. The five types of building construction each have their own strengths and weaknesses and differing levels of resistance to fire. Buildings contain a variety of parts or components. Materials used in building components vary.