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Building Construction

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Objectives (1 of 3)

• Describe the characteristics of the following building materials: masonry, concrete, steel, glass, gypsum board, and wood.

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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.

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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.

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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

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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

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Construction Material Properties and Fire Behavior

• Key factors affecting combustibility:– Combustibility– Thermal conductivity– Loss of strength when heated– Rate of thermal expansion

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Types of Construction Materials

• Masonry• Concrete• Steel and other metals• Glass• Gypsum board• Wood• Plastics

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Masonry

• Inherently fire-resistive

• Poor conductor of heat

• Openings can allow fire to spread.

• With prolonged exposure to fire, masonry can collapse.

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Concrete

• Inherently fire-resistive

• Poor conductor of heat

• Strong under compression

• Weak under tension

• Can be damaged through exposure to fire

– Spalling

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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

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Steel (2 of 2)

• Expands and loses strength when heated

• Any sign of bending, sagging, or stretching indicates immediate risk of failure.

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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

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Glass

• Noncombustible, but not fire-resistive

• Ordinary (non-treated) glass will break when exposed to flame.

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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

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Gypsum Board (2 of 2)

• Prolonged exposure to fire will cause failure.

– Moisture in the material will evaporate causing deterioration.

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Wood

• Most common building material

• Highly combustible

• Weakens when heated

• Fire-retardant chemicals can weaken wood.

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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.

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Construction Type Determination

• Classification based on combustibility and fire resistance

• Codes specify construction type required based on:

– Height– Area– Occupancy– Location

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Types of Construction

• Type I: Fire-Resistive

• Type II: Noncombustible

• Type III: Ordinary

• Type IV: Heavy Timber

• Type V: Wood Frame

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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

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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.

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Type II: Noncombustible (1 of 2)

• All structural components must be noncombustible.

• Fire-resistive requirements are less stringent than Type I.

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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

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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

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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.

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Type IV: Heavy Timber (1 of 2)

• Exterior masonry walls

• Interior structural elements, floors, and roof of wood

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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.

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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

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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

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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.

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Building Components

• Foundation

• Floors and ceilings

• Roofs

• Trusses

• Walls

• Doors and windows

• Interior finishes and floor coverings

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Foundation

• Ensures building is firmly planted

• Helps keep all other components connected

• Weak or shifting foundations can cause collapse.

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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.

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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

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Roofs

• Not designed to be as strong as floors

• Three primary designs:– Pitched roofs– Curved roofs– Flat roofs

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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

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Curved Roofs

• Used for large buildings that require large, open interiors

– Supermarkets– Warehouses– Industrial buildings

• Usually supported by bowstring trusses or arches

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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.

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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.

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Trusses (1 of 2)

• Triangular geometry creates a strong, rigid structure.

• Usually prefabricated wood or steel

• Three types:– Parallel chord– Pitched chord– Bowstring

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Trusses (2 of 2)

• Parallel chord– Used for flat roofs and floors

• Pitched chord– Used for pitched roofs

• Bowstring– Used for curved roofs

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Walls

• Most visible part of a building

• Constructed of a variety of materials

• Walls are:– Load-bearing– Nonbearing– Specialized

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Load-Bearing Walls

• Give structural support

• Either interior or exterior

• Support both “dead load” and “live load”

• Damaged wall can result in collapse

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Nonbearing Walls

• Support only their own weight

• Can be breached or removed without compromising structural integrity

• Either interior or exterior

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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

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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

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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.

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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.

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Window Assemblies

• Used for light, ventilation, entry, and exit

• Window type depends on a variety of factors.

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Fire Doors and Fire Windows(1 of 2)

• 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

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Fire Doors and Fire Windows(2 of 2)

• Fire windows are used when a window is needed in a required fire-resistant wall.

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Interior Finishesand Floor Coverings

• Finishes and coverings are exposed interior surfaces of a building.

• Different interior finish materials contribute in various ways to a building fire.

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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

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Summary (1 of 2)

• 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.

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Summary (2 of 2)

• Buildings contain a variety of parts or components.

• Materials used in building components vary.

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