Building Construction

Building Construction

6 Objectives (1 of 3) • Describe the characteristics of the following building materials: masonry, concrete, steel, glass, gypsum board, and wood.

6 Objectives (2 of 3) • List the characteristics of each of the following types of building construction: fire-resistive construction, noncombustible construction, ordinary construction, heavy timber construction, and wood-frame construction.

6 Objectives (3 of 3) • 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.

6 Introduction (1 of 2) • Knowing building construction enables fire fighters to: • Predict how a fire will spread • Make determinations about structural integrity • Recognize warning signs of imminent collapse

6 Introduction (2 of 2) • Fire risks also depend on occupancy and contents. • Occupancy: how a building is used • Contents: vary, but usually related to building use

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

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

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

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

6 Steel (1 of 2) • 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

6 Steel (2 of 2) • Expands and loses strength when heated • Any sign of bending, sagging, or stretching indicates immediate risk of failure.

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

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

6 Gypsum Board (1 of 2) • 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

6 Gypsum Board (2 of 2) • Prolonged exposure to fire will cause failure. • Moisture in the material will evaporate causing deterioration.

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

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.

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

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

6 Type I: Fire-Resistive (1 of 2) • All structural components must be noncombustible. • Used for: • Large numbers of people • Tall or large area • Special occupancies

6 Type I: Fire-Resistive (2 of 2) • 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.

6 Type II: Noncombustible (1 of 2) • All structural components must be noncombustible. • Fire-resistive requirements are less stringent than Type I.

6 Type II: Noncombustible (2 of 2) • Structural components contribute little or no fuel. • Fire severity is determined by contents. • Most common in single-story warehouses or factories

6 Type III: Ordinary (1 of 2) • 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

6 Type III: Ordinary (2 of 2) • Two separate fire loads: • Construction materials • Contents • Fire resistance depends on building age and local building codes. • Exterior walls, floors, and roof are connected.

6 Type IV: Heavy Timber (1 of 2) • Exterior masonry walls • Interior structural elements, floors, and roof of wood

6 Type IV: Heavy Timber (2 of 2) • 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.

6 Type V: Wood Frame (1 of 3) • Most common type of construction in use • All major components are wood or other combustible materials. • Can rapidly become fully involved • Collapse frequently

6 Type V: Wood Frame (2 of 3) • 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

6 Type V: Wood Frame (3 of 3) • Balloon-frame construction • Exterior walls assembled with continuous wood studs from the basement to the roof. • Platform-frame construction • Exterior wall studs not continuous.

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

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

6 Floors and Ceilings (1 of 2) • Fire-Resistive 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.

6 Floors and Ceilings (2 of 2) • 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

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

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.

6 Trusses (1 of 2) • Triangular geometry creates a strong, rigid structure. • Usually prefabricated wood or steel • Three types: • Parallel chord • Pitched chord • Bowstring

6 Trusses (2 of 2) • Parallel chord • Used for flat roofs and floors • Pitched chord • Used for pitched roofs • Bowstring • Used for curved roofs

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

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

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

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

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

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.

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.

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

Building Construction