6
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 woodframe 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.
2
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
3
6
Construction Material
Properties and Fire Behavior
• Key factors affecting combustibility:
– Combustibility
– Thermal conductivity
– Loss of strength when heated
– Rate of thermal expansion
4
6
Types of Construction
Materials
•
•
•
•
•
•
•
Masonry
Concrete
Steel and other metals
Glass
Gypsum board
Wood
Plastics
5
6
Masonry
•
•
•
•
Inherently fireresistive
Poor conductor of
heat
Openings can allow
fire to spread.
With prolonged
exposure to fire,
masonry can
collapse.
6
6
Concrete
•
•
•
•
•
Inherently fire-resistive
Poor conductor of heat
Strong under compression
Weak under tension
Can be damaged through exposure to
fire
– Spalling
7
6
Steel
• 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.
8
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
9
6
Glass
•
•
Noncombustible, but not fire-resistive
Ordinary (non-treated) glass will break
when exposed to flame.
10
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.
11
6
Wood
•
•
•
•
Most common building material
Highly combustible
Weakens when heated
Fire-retardant chemicals can weaken
wood.
12
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.
13
6
Construction Type Determination
•
•
Classification based on combustibility
and fire resistance
Codes specify construction type
required based on:
–
–
–
–
Height
Area
Occupancy
Location
14
6
Types of Construction
•
•
•
•
•
Type I: Fire-Resistive
Type II: Noncombustible
Type III: Ordinary
Type IV: Heavy Timber
Type V: Wood Frame
15
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.
16
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
17
6
Type III: Ordinary
• 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.
18
6
Type IV: Heavy Timber
•
•
•
•
•
•
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.
19
6
Type V: Wood Frame (1 of 2)
• 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
20
6
Type V: Wood Frame (2 of 2)
• Balloon-frame
construction
– Exterior walls assembled
with continuous wood
studs from the basement
to the roof.
• Platform-frame
construction
– Exterior wall studs not
continuous.
21
6
Building Components
•
•
•
•
•
•
•
Foundation
Floors and ceilings
Roofs
Trusses
Walls
Doors and windows
Interior finishes and floor coverings
22
6
Foundation
• Ensures building is
firmly planted
• Helps keep all other
components
connected
• Weak or shifting
foundations can
cause collapse.
23
6
Floors and Ceilings
• 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.
•
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
24
6
Roofs
•
•
Not designed to be as strong as floors
Three primary designs:
– Pitched roofs
– Curved roofs
– Flat roofs
25
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
26
6
Curved Roofs
•
Used for large buildings that require
large, open interiors
– Supermarkets
– Warehouses
– Industrial buildings
•
Usually supported by bowstring
trusses or arches
27
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.
28
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.
29
6
Trusses
•
•
•
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
30
6
Walls
• Most visible part of a building
• Constructed of a variety of materials
• Walls are:
– Load-bearing
– Nonbearing
– Specialized
31
6
Load-Bearing Walls
• Give structural support
• Either interior or
exterior
• Support both “dead
load” and “live load”
• Damaged wall can
result in collapse
32
6
Nonbearing Walls
• Support only their
own weight
• Can be breached or
removed without
compromising
structural integrity
• Either interior or
exterior
33
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
34
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
35
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.
36
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 fireresistant.
37
6
Window Assemblies
• Used for light,
ventilation, entry,
and exit
• Window type
depends on a
variety of factors.
38
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.
39
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.
40
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
41
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.
42