HomeMy WebLinkAboutBuilding Construction Guide Fresno Fire Department
December 2020 Page 1
Fresno Fire Department Building Construction Guide
Fresno Fire Department
December 2020 Page 2
Current Revision Date: 12/08/2021 Next Revision
Date:
12/08/2024
Reviewer Name/Rank: Dave Doss, Captain Review Level: 1
Administrative
Support:
Manuel Graves, Civilian
Training Officer
ADA
Table of Contents
INTRODUCTION ................................................................................................... 5
Structural Integrity .............................................................................................. 5
Ladder Placement .............................................................................................. 6
Forcible Entry/Search and Rescue ..................................................................... 6
Ventilation Feasibility .......................................................................................... 6
Size-Up............................................................................................................... 7
CONSTRUCTION STYLES ................................................................................... 9
Conventional Construction ................................................................................. 9
ROOF STYLES .................................................................................................... 11
Gable Roof ....................................................................................................... 11
Hip Roof ........................................................................................................... 13
Bridge Truss Roof ............................................................................................ 14
Bowstring Arch Roofs ....................................................................................... 16
Lamella Arch Roof ............................................................................................ 17
Tied Truss Arch Roofs ...................................................................................... 17
Sawtooth Roof .................................................................................................. 18
Conventional Flat Roof ..................................................................................... 19
Wooden I Beam Roof ....................................................................................... 20
Nailing Block ..................................................................................................... 21
Open Web Roof ................................................................................................ 21
Metal Gusset Plate Roof................................................................................... 23
Panelized Roof ................................................................................................. 24
Open Web Bar Joist Roof/Parallel Truss .......................................................... 27
Lightweight Concrete Roof (Non-Structural) ..................................................... 28
METAL CONSTRUCTION METHODS ................................................................ 29
Corrugated ....................................................................................................... 29
Metal Beam ...................................................................................................... 29
CONCRETE CONSTRUCTION METHODS ........................................................ 31
Tilt Up ............................................................................................................... 31
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MASONRY CONSTRUCTION METHODS .......................................................... 32
Pre-1933 ........................................................................................................... 32
Post 1933 ......................................................................................................... 33
Post 1959 ......................................................................................................... 34
Post 1971 ......................................................................................................... 34
Considerations ................................................................................................. 37
Block ................................................................................................................ 38
FRAME / STUCCO CONSTRUCTION METHODS .............................................. 39
Facades............................................................................................................ 39
BUNGALOW AND BALLOON CONSTRUCTION ................................................ 43
CURTAIN CONSTRUCTION METHODS ............................................................ 45
AGE OF THE BUILDING ..................................................................................... 47
Pre-1933 ........................................................................................................... 47
1933 to Late 1950's .......................................................................................... 47
1950's to Present .............................................................................................. 47
IMPACT OF LIGHTWEIGHT ................................................................................ 48
CONSTRUCTION ON FIREGROUND DECISIONS ........................................ 48
Identification ..................................................................................................... 48
Communication ................................................................................................ 48
Time ................................................................................................................. 48
Operations ........................................................................................................ 48
DEFINITIONS ...................................................................................................... 49
REFERENCES .................................................................................................... 50
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PURPOSE
The Fresno Fire Department responds to a multitude of building types daily. A
proper understanding of building construction techniques and the ability to identify
and respond to changing fireground conditions are essential to safe and effective
firefighting operations. The purpose of this guide is to provide a basic overview of
building construction.
APPLICATION
This guide intended to follow industry recommendations and standards and was
based largely on Los Angeles Fire Department Book 29 Building Construction. The
Fresno Fire Department thanks innovators in the fire service for their contributions
in keeping firefighters safe and trained.
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INTRODUCTION
As architects and the building industry continue to design and build structures that
vary in type, design, materials, and building methods, it has become increasingly
important that members stay familiar with both basic and new concepts of building
construction. Construction methods are constantly being replaced by new and
more efficient and cost effective methods to construct buildings.
Unfortunately, new construction methods are usually NOT designed to assist fire
suppression operations. Considering the cost of labor, equipment, and building
materials, it is not economically feasible to build a structure in the same manner as
during the period of conventional construction. Heavy timbers have been replaced
by smaller dimension lumber, and petrochemical based compounds have replaced
conventional building materials, regardless of building size.
As architects reduce the mass and change the chemical composition of building
materials, we are losing one of our most valuable factors: time.
Basically, we tend to fight structure fires the same way we did 40 to 50 years ago.
Hose lines are taken inside an involved structure, and holes are opened in roofs for
ventilation.
So, are buildings the same as the buildings constructed during the 1920’s and
1930's? They are not even close! Therefore, Firefighters who can recognize the
strengths and hazards of buildings and roofs will increase their efficiency and
safety. A working knowledge of building construction not only provides the
necessary expertise to conduct a quick and accurate size-up of a structure; it also
provides the foundation for effective, timely, and safe fireground operations in the
following areas:
Structural Integrity
Ladder Placement
Forcible Entry / Search and
Rescue
Ventilation Feasibility
Structural Integrity
The effects from fire on a particular type of construction, building or roof, should be
evaluated to determine the remaining time necessary to conduct safe fireground
operations.
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The integrity of a working surface (i.e., roof and floor decking) must be evaluated
for safe operations.
Ladder Placement
Ladders should be placed to the strong area of a building. This results in stability
and strength for ladder operations.
Special hazards such as facades must be recognized and avoided.
Figure 1 Ladder Placement
Forcible Entry/Search and Rescue
What are the best avenues to enter the structure?
What is the probable floor plan of the structure?
Ventilation Feasibility
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Figure 2 - Truck Crew on Roof
Can a ventilation operation be safely conducted?
Safe routes of travel for personnel across a roof must be determined.
Additionally, the direction of structural members (rafters/joists) must be determined
prior to initiating ventilation to enhance safe and effective cutting operations.
Size-Up
Mental evaluations can be developed based on current knowledge.
A plan of action can be formulated based on perceived factors (occupancy type,
exposure, involvement on arrival, etc.)
A common definition of this well used term is as follows: "Size-up (estimate of the
situation) is a mental evaluation that assists in determining a course of action and
the methods necessary to accomplish a desired goal." Basically, a size-up consists
of three operations as follows:
1. Analyze the situation.
2. Decide on a plan. (strategy)
3. Put the plan into operation.(tactics)
Now, let’s focus on the first portion of size-up, "analyzing the situation." When this
portion of a size-up is applied to a structure fire, one of the first considerations
should be the type and construction of the building. These two factors will indicate:
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Rate of burning.
Possible avenues of fire spread. (False ceilings, multiple attics, facades,
etc.)
Problems that will have a direct impact on efforts to confine a fire.
Structural integrity.
Time necessary to conduct safe fireground operations.
When these factors are quickly and confidently evaluated, a useful overview of the
structure will result. Due to the fact that the building industry is continuing to
construct various types of buildings in an endless combination of construction
materials, methods and styles, identification of buildings and their related strengths
and hazards can be challenging at best. Therefore, let's consider a simple method
to visually size-up old and new construction methods and styles to assist in
determining related strengths and hazards. Additionally, when conducting a
building size-up, "undress" the building in your mind. Look past the exterior of a
building and visualize what is INSIDE (strengths and hazards) the building. Our
size-up will focus on the following areas:
Construction Styles
Roof Styles
Construction Methods
Metal Concrete
Masonry
Frame/Stucco
Curtain
Age of the Building.
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CONSTRUCTION STYLES
Conventional Construction
Conventional construction utilizes structural members that depend on size for
strength. The greater the span for a structural member, the larger it has to be to
support a given load. Additionally, conventional construction does not usually
depend on the sum total of all structural parts or members for its strength. Structural
members depend on their size for strength.
SIZE = STRENGTH. This can be easily demonstrated by considering mill/timber
construction. Structural members may be 8 x 8 inches for strength. The size of
structural members dictates the time necessary for failure when exposed to heat or
fire.
Lightweight Construction
Unlike conventional construction, lightweight truss construction does not derive
strength from size. Strength is obtained from multiple members that are in
compression and tension. The strength of the individual structural member is
dependent on the total sum of the other members; therefore, if one member fails,
others may fail.
COMPRESSION / TENSION = STRENGTH
(LESS THAN AVERAGE WEIGHT / SIZE)
Figure 3. Lightweight Construction Truss System
A single lightweight truss structural member can span 70-feet and may be
comprised of 2 x 4's in compression and tension to form an integral unit. Although
this structural member is strong, the size of the individual members is relatively
small, requiring less time for structural collapse when exposed to heat or fire.
Let's briefly compare some of the major differences between conventional and
lightweight construction and what can be expected when they are exposed to fire:
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As previously mentioned, conventional construction does not rely on a sum total of
members for strength. A simple example is a gable roof in a dwelling. The ridge
board and rafters are an integral unit. However, they are separate and distinct from
the ceiling joists. Therefore, when the attic is exposed to fire, the rafters and roof
may collapse on the ceiling joists, thereby preventing collapse onto firefighting
personnel below.
Lightweight construction is vastly different due to truss construction that depends
on the sum total of members for strength. When a truss gable roof in a dwelling is
exposed to sufficient fire, expect the rafters (top chord of the truss), the roof decking,
and ceiling joists (bottom chord of the truss) to collapse as a unit into the structure,
exposing firefighting personnel to falling, burning debris. There is no comparison
between the size of the wood in conventional and lightweight construction. With
few exceptions, 2-in x 3-in and 2-in x 4-in are the standard for lightweight
construction, while conventional construction will utilize a minimum of 2-in x 4-in
(and up to mill/timber construction).
Figure 4. Common Lightweight Roof Truss
This translates into time that must be considered when deploying personnel and
evaluating an offensive or defensive operation. Remember, the ability to accurately
estimate the amount of time that a structure can be considered structurally strong
is dependent on the following factors:
Type of Construction
How long the fire has been burning
Fire Intensity
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ROOF STYLES
For size-up considerations, roof styles can be divided into the following categories:
Gable
Hip
Flat
Bridge Truss
Arch
Sawtooth
Let's expand on each of these roofs and consider their construction, strengths, and
hazards.
Gable Roof
A-frame configuration of conventional or ordinary construction that consists of a
ridge board and rafters that cross the outside walls. Rafters are usually 2 x 6 inches
or larger and are usually 16 inches to 24 inches "on-center."
Figure 5. Conventional Roof System
Additional support is provided by collar beams and ceiling joists. This roof is found
in semi-flat to steep pitch configurations. As detailed earlier in this section, 2 x 6
inch rafters (spaced up to 36 inches "on center" for steep pitched roofs) were
commonly utilized for roof structural members. Additionally, the ridge was
comprised of 1 x 6 inch ridge board or the lack of a ridge board which resulted in
the 2 x 6 inch rafters butted together.
Lightweight construction utilizes 2 x 3, or 2 x 4 inch wood trusses held together by
metal gusset plate connectors. Truss systems are enjoying widespread use in roof,
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floor and rough window and door openings. Trusses share common features such
as top chords, bottom chords, and webbing.
Figure 6. Common Lightweight Truss System
Metal gusset place connectors may vary in size, thickness, and depth of
penetration. The most common are 18 gauge steel plates with prongs that
produce 3/8 inch penetration.
The bottom chord of the truss has replaced the 2 x 4 inch (or larger) ceiling joist
found in conventional construction.
A point of interest with this type of lightweight construction (which also applies to
open web and wooden "I" beam construction) is the fact that truss members may
only be supported at their outside edges (unless used as a cantilever truss).
Interior partition walls may not support the truss at any point along the bottom chord.
Eighteen-gauge "roof truss clips" may be found nailed to the bottom chord (every
three to five trusses) and top plate of interior walls. Roof truss clips provide some
stability for interior partition walls. In this configuration, interior partition walls
could be classified as "free standing." Common "on-center" spacing for truss
rafters is 24 inches.
Strengths
Conventional construction utilizes ridge boards and rafters of 2 x 6 inches or larger.
This type of construction will last longer (compared to 2 x 4 inch trusses) when
exposed to fire. The strong areas of this roof are the ridge and the area where the
rafters cross the outside walls.
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Figure 7. Conventional Construction Gable Roof
Hazards
The use of 2 x 4 inch rafters with no ridge board is similar in appearance, size and
structural integrity to lightweight 2 x 4 inch trusses. This similarity will also apply to
a reduced burning time and potential early failure rate and collapse of the roof.
Utilization of 2 x 3 or 2 x 4 inch trusses with metal gusset plate connectors equals
a short burning time and potential early failure rate and collapse. Trusses are under
tension and compression and when the bottom chord or webbing fails trusses will
fail. Rapid collapse is common. When metal connector plates and surrounding
wood are exposed to fire, the connector plates will quickly fail by pulling out from
the wood.
The bottom chord of the truss has replaced the 2 x 4 inch (or larger) ceiling joist of
conventional construction. Coupled with the fact that bottom chords may not rest
on the interior walls (which offer additional support), expect collapse of the entire
roof in a short period of time.
Newer roofs use 3/8 or ½ inch plywood as a decking instead of 1 x 4 inch or 1 x 6
inch space sheathing. Plywood will burn and fail at a faster rate than sheathing and
offers minimal resistance to fire. Particle, chip and strand board are also currently
utilized as a decking in an effort to reduce building costs and can be more
hazardous than plywood.
Hip Roof
Similar to the gable roof; notice the lack of the A-frame configuration. Ends of the
roof terminate in a "hip" configuration. Conventional or ordinary construction
consists of a ridge board, hip rafters from the ridge board down to and across the
corners at the outside walls.
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Figure 8. Hip Roof Conventional Construction
Valley rafters are utilized where two roof lines join together. Jack and common
rafters complete the structural members. The ridge board and rafters are usually 2
x 6 inches or larger. Rafters are usually 16 to 24 inches "on center," similar to the
gable roof. "Rough cut" 2 x 3 or 2 x 4 inch rafters 36 inches "on-center" was also
utilized in older wood frame structures with steep pitched roofs.
In lightweight construction, construction methods are similar to those used for gable
roofs. Various degrees of pitch are characteristic in this style of roof.
Strengths
Ridge board, valley rafters, hip rafters, and the area where rafters cross the outside
walls are areas of strength. In conventional construction, ridges and rafters are 2 x
6 inches or larger.
Hazards
Similar to gable roofs. Utilization of 2 x 3 or 2 x 4 inch rafters or trusses will produce
similar results to 2 x 4 inch rafters and lightweight trusses in gable roofs when
exposed to fire. Roofs with a steep pitch may require roof ladders to conduct
ventilation operations. If the roof is covered with tile or other similar materials, the
roof will become slippery when wet and offers minimal footing when dry.
Additionally, tile and other related materials need to be removed prior to roof
ventilation operations.
Bridge Truss Roof
These roofs are found on various types and sizes of commercial buildings primarily
constructed during the 1930's and 1940's. Wooden truss members are built from
2 x 12 inch lumber.
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Figure 9. Bridge Truss Roof
This usually constitutes a heavy grade of construction. Metal tie rods may be used
vertically for additional support. Rafters are 2 x 6 inches or larger and covered by
1 x 6 inch sheathing (diagonal or straight) and composition roofing material.
Straight sheathing was utilized prior to 1933, and diagonal sheathing was
utilized after 1933. Plywood decking (installed over existing) is utilized, if modified
for the Earthquake Ordinance.
Strengths
Well-constructed. When exposed to fire, early collapse of main structural members
should not be a primary concern. However, depending on the type of fire, this roof
predictably fails in sections. This roof is easily identified by its characteristic
sloping ends.
Figure 10. Sloping Ends of Bridge Truss
Hazards
Strength is dependent on the size of lumber utilized and the span of trusses. The
trusses are in tension and compression and may fail under severe fire
conditions. The underside of the roof is usually common to the interior of
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commercial warehouse type structures, or the bridge trusses can be modified to
allow storage in the attic area or ceilings (the bottom chords can be covered with
sheathing or plywood) (and/or lath and plaster, etc. can be attached to the bottom
chord of the trusses. These factors can contribute to early collapse of the
trusses and roof. If the roof has been modified for the Earthquake Ordinance,
ventilation personnel must be aware of plywood, metal straps and supports.
Bowstring Arch Roofs
Similar to the bridge truss roof. This popular type of roof was constructed during
the 1930's, 1940's, and 1950's on both small and large commercial type structures.
Figure 11. Bow String Construction
Usually a large size (2 x 12 or 2 x 14 inch) of lumber comprises the arch trusses
and related members. Some arch trusses have multiple beams forming one truss
arch. Rafters are 2 x 6 inches or larger and covered by 1 x 6 inch sheathing
(diagonal or straight) and composition roofing material. Straight sheathing was
utilized prior to 1933, and diagonal sheathing was utilized after 1933. Plywood
decking (on top of the sheathing) is utilized, if modified for the Earthquake
Ordinance.
Strengths
Most roofs of this type are well constructed. When exposed to fire, early structural
collapse of the arched trusses should not be a primary concern. Similar to the
bridge truss roof, it usually fails in sections, depending on the type of fire and
structural integrity of the roof.
Hazards
Strength is dependent on the size of lumber utilized and the span of trusses. The
trusses are in tension and compression and may fail under severe fire
conditions. The underside of the roof is usually common to the interior of
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commercial warehouse type structures, or the arch trusses can be modified to allow
storage in the attic area or ceilings (the bottom chords can be covered with
sheathing or plywood) (and/or lath and plaster, etc., can be attached to the bottom
of chord of the trusses. These factors can contribute to early collapse of the trusses
and roof. If the roof has been modified for the Earthquake Ordinance, ventilation
personnel must be aware of plywood, metal straps and supports.
Lamella Arch Roof
Lamella Arch Roofs are an egg crate, geometric or diamond-patterned roof,
constructed from 2 x 12 inch wood framing with steel plates and bolts at junctions
of framing. Roof decking is 1 x 6 inch sheathing and composition roofing material.
This type of an arch roof is supported by exterior buttresses or internal tie rods with
turnbuckles, and is common on gymnasiums, large buildings used for recreational
activities, large supermarkets, etc.
Figure 12. Lamella Arch Roof
Strengths
Solidly built, with good construction techniques and lumber.
Hazards
Although these roofs offer some protection when exposed to fire, total roof
collapse may occur if fire removes more than 20-percent of the roof structure.
Total roof collapse of the roof can result from "the domino effect”.
Tied Truss Arch Roofs
Although this roof is similar in appearance to bowstring arch and lamella roofs, it is
significantly different in that it is an arched roof that uses metal tie rods to offer
lateral support for the walls of the building.
Tie rods (usually 5/8 inch in diameter) with turnbuckles are used below each arch
member to ensure the arches do not push the exterior walls outward. Tie rods may
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pass through exterior walls outside plates, which facilitate identification of this style
of roof. Proper tie rod tension is maintained by turnbuckles.
Top chords of arch member may utilize laminated 2-in x 12-in or large members.
Rafters are 2-in x 10-in or larger and covered by 1-in x 6-in sheathing (diagonal or
straight) and composition roofing material. Straight sheathing was utilized prior to
1933, and diagonal sheathing was utilized after 1933. Plywood decking (on top of
the sheathing) is utilized, if modified for the Earthquake Ordinance.
Strengths
This type of roof utilizes a large size of lumber (2-in x 12-in or larger) and 1-in x 6-
in sheathing as the roof decking.
Hazards
The primary hazard of this roof is early failure of the metal tie rods and turnbuckles.
The tie rods, which are in tension, provide lateral support for the exterior walls and
prevent the arches, which are in compression, from pushing the exterior walls
outward and collapsing the building. Due to the fact that this roof (and its
relationship to the building) is dependent on the strength and security of the
tie rods, roof failure may occur in sections when exposed to fire. However,
the roof may be susceptible to total failure depending on the type of fire.
Sawtooth Roof
Used on commercial buildings to yield additional light and ventilation for
manufacturing type occupancies.
Figure 13. Sawtooth Roof
It is constructed with rafters of 2 x 8 inches or larger and utilizes wood and/or metal
supports for bracing. The sloping portion is covered with 1 x 6 inch sheathing (or
½ inch plywood in newer roofs) and composition roofing material. This type of roof
is basically constructed the same today as it was during the 1930's and 1940's.
Strengths
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Well-constructed. When exposed to fire, early collapse of main structural members
should not be a primary concern. Additionally, this type of roof is easy to ventilate;
utilize the hinged panes of glass.
Hazards
The underside of these roofs can be considered as open or exposed to the
structure. Newer sawtooth roofs are covered with ½ inch plywood. Plywood
decking will yield little resistance to fire. If this roof has been modified for the
Earthquake Ordinance, ventilation personnel must be aware of plywood, metal
straps and supports.
Conventional Flat Roof
Wood rafters of various sizes (2 x 6 inches and larger) are laid across outside walls,
or outside wall to interior walls/structural supports. Rafters are covered with 1 x 6
inch sheathing or plywood (in newer applications) and composition roofing material.
Figure 14. Conventional Flat Roof
Some lightweight roofs are similar in design, but the rafters are replaced with
lightweight construction, making it important not to mistake lightweight construction
for conventional flat construction.
Strengths
Susceptibility to fire is totally dependent on the size of the rafters, their "on-center"
spacing and the type of decking that has been utilized. Consider the perimeter of
the building a strong point.
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Hazards
The degree of hazard is determined by the rafters, span, size, on-center spacing,
and the presence of metal hangers used to suspend the rafters. If this roof has
been modified for the Earthquake Ordinance, ventilation personnel must be aware
of plywood, metal straps and supports.
Newer conventional flat roofs covered with plywood instead of sheathing will
present a significant problem. Plywood which may be found in 3/8 inch to 5/8 inch
thickness’ offer minimal structural integrity under fire conditions. Plywood roof
decking may be burned out (plywood "layers" comes when exposed to heat and/or
fire) from the underside of the roof. New applications are utilizing "particle or
chip board" for decking applications.
Wooden I Beam Roof
Figure 15. Wooden I Beam Roof
Wooden I Beam construction consists of top and bottom parallel wooden chords
that are connected by a wooden stem. The top chord, which is under a load, offers
a bridging effect causing the top chord to be in compression and the bottom chord
member to be in tension. Open web construction is prefabricated at the factory
before installation.
Two-by-fours are used as chords, but 2 x 3 inch chords are common. Some chords
may resemble plywood due to horizontal (or longitudinal) laminations. However,
this is a trade lamination process that enables a low grade of lumber to be
used for structural members. The stem is joined to the top and bottom chords
by a continuous glued-edge joint and may be constructed from 3/8 inch plywood or
"chip-board" of the same thickness. When these prefabricated joists are installed
in a building, top chord members can be secured (metal hangers) to the top of
bearing walls with the bottom chord member remaining unsupported and away from
the wall, or the bottom chord member can be secured to the top of bearing walls
with the top chord unsupported and above the wall.
The common on-center spacing is 24 inches. Nailing blocks are placed
perpendicular to the top chords and are spaced four feet apart. This provides an
additional nailing surface for the 4' x 8' sheets of plywood.
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Nailing Block
When plywood decking is nailed to structural members a method termed
"diaphragm nailing" is employed. Prior to nailing, the plywood sheets are placed so
the 8-foot dimension crosses the roof structural members, and the 4-foot dimension
parallels the roof structural member. The joints of the plywood are then staggered
(every 4') similar to a masonry wall.
Figure 16. Nailing Blocks
Strengths
Consider the perimeter of the building where the roof ties into the exterior walls a
strong area.
Hazards
What there is to burn consists of 3/8 inch stem and 2 x 3 inch or 2 x 4 inch chords
in tension and compression. It will take little time for the 3/8 inch stem to burn,
weaken, and cause collapse of the truss chords and roof that has been sufficiently
undermined by fire. Buildings will be found with open and unprotected chords.
Common practice is to run heating and air conditioning ducts of various sizes
through the stems which removes a significant percentage of the stem and gives
fire horizontal access to adjacent "I" beams, assisting the travel and spread of fire.
Due to the size of lumber and the chord members in tension and compression,
expect rapid failure of this roof when exposed to fire. Plywood will burn and
fail at a fast rate and offers little resistance to fire. Ventilation personnel must be
aware of nailing blocks when cutting between and parallel to the top chords.
Open Web Roof
Open web construction consists of top and bottom parallel wooden chords that are
cross-connected by steel tube web members. The top chord (supported) which is
under a load, offers a bridging effect causing the top chord to be in compression
and the bottom chord member (unsupported) to be in tension.
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Open web construction is prefabricated at the factory before installation and is
constructed with either parallel chords laid on edge or flat laid chords. The steel
tube web members are prefabricated from one to two inch cold rolled steel tubing
with the ends pressed flat into a semicircular shape with a hole punched through
the end. These flattened ends are inserted into slots in the chords and steel pins
(up to one inch) are driven through the chord members and flattened ends of the
web member, completing the assembly. Spans to 70-feet are possible using a
single 2’ x 4’ or two 2’ x 3's as top and bottom chord members. A single 2 x 4 up to
70 feet is made possible by joining different lengths in glued, mitered "finger joints."
Figure 17. Open Web Truss
When these prefabricated joists are installed in a building, top chord members can
be secured (metal hangers) to the top of bearing walls with the bottom chord
member remaining unsupported and away from the wall, or the bottom chord
member can be secured to the top of bearing walls with the top chord unsupported
and above the wall.
The common on-center spacing is 24 inches. Nailing blocks are placed
perpendicular to the top chords and are spaced four feet on center. This provides
an additional nailing surface for the 4' x 8' sheets of plywood. When plywood
decking is nailed to structural members, a method termed "diaphragm nailing" is
employed. Prior to nailing, the plywood sheets are placed so the 8-foot dimension
crosses the roof structural members, and the 4-foot dimension parallels the roof
structural member. The sheets of plywood are then staggered.
Strengths
Consider the perimeter of the building where the roof ties into the exterior walls a
strong area.
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Hazards
What there is to burn consists of cold rolled steel, 2 x 3 inch or 2 x 4 inch chords in
tension and compression. It will take little time to burn, weaken, and cause collapse
of the truss chords and roof that have been sufficiently undermined by fire.
Buildings will be found with open and unprotected chords. Expect to find a lack of
fire stops in this construction. Due to the size of lumber and the chord members in
tension and compression, expect rapid failure of this roof when exposed to fire.
Plywood will burn and fail at a fast rate and offers little resistance to fire. Ventilation
personnel must be aware of nailing blocks when cutting between and parallel to the
top chords.
Metal Gusset Plate Roof
Figure 18. Metal Gusset Plate
Wood trusses predominantly composed of 2 x 4's that are held together by metal
gusset plate connectors. Trusses for roofs are constructed in a wide variety of
shapes (flat, gable, hip, etc.) all shapes share common features.
Figure 19. Metal Gusset Truss System
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Trusses consist of top chords, bottom chords and webbing (supports between the
top and bottom chords). These trusses are held together by “metal gusset plate”
connectors that vary in size, thickness and depth of penetration. Eighteen-gauge
steel plates with prongs that produce 3/8 inch penetration are common and used
in a wide variety of applications. Utilization of 2-in x 4-in in a span of up to 80 feet
may be found in flat metal gusset plate roofs. Decking material is usually ½ inch
plywood. Dwellings will use 3/8-in or ½-in plywood.
Strengths
Consider the strong area to be where the trusses cross (cantilever applications) or
terminate on the outside bearing walls.
Hazards
The material exposed to fire consists of 2-in x 4-in trusses chords in tension and
compression with metal gusset plate connectors. It will take little time to burn,
weaken, and cause collapse of the truss chords and roof that have been
sufficiently undermined by fire. Whether from connector plates that have pulled
out or from deep char, a truss or multiple trusses will fail. In dwellings, rapid and
total collapse is common.
Plywood will burn and fail at a fast rate and offers little resistance to fire. These
roofs will often retain their shape as the plywood is burning through. Ventilation
personnel must be aware of nailing blocks when cutting between and parallel to the
top chords.
Panelized Roof
Figure 20. Panelized Roof
This roof may be found on wood, masonry or concrete tilt up slab buildings. It
consists of four major components:
Beams (laminated wood or metal)
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Purlins
2 x 4 inch joists
2 inch plywood decking
Figure 21. Panelized Roof Framing
After the walls are erected, the roof is usually constructed in the following manner:
Laminated beams of various sizes (6 x 36 inch is common) are initially installed
spanning the length or width of the building. Beams are supported at their ends by
pilasters, wood or steel posts, or saddles. Wood or steel posts may provide
additional support along the span. These beams are spaced between 12 and 40
feet apart. Beams may be bolted together to provide lengths well in excess of 100
feet. Supported by these beams, wooden purlins are installed with metal hangers
on 8 foot centers (a sheet of plywood is eight feet long).
A common size for a purlin is 4 x 12 inches with the length depending on the spacing
of the beam. Metal gusset plate trusses are beginning to be substituted for
conventional purlins, resulting in substantial cost savings as well as an additional
collapse hazard.
Hazards
Joists measuring 2 x 4 inches by eight feet are installed with metal hangers on 24
inch centers between the purlins, parallel to the beams. Sheets of 4 x 8 feet x ½
inch plywood are nailed over this framework. The plywood decking is then covered
with composition roofing material.
Strengths
The strengths of this roof are:
Beams
Purlins
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Building Perimeter
Hazards
Beam span supports of 4-inch hollow steel pipe may be found. Expect weakening
and/or collapse of these supports with failure of large portions of the roof under
heavy fire conditions.
Figure 22. Panelized Roof, notice the nailing blocks and joist hangers
Moderate to heavy fire intensities will quickly burn through the 2 x 4 inch joists and
1/2 inch plywood decking, which may result in vertical travel of the fire and a
reduction in horizontal fire spread. When the insulation (kraft paper) is subjected
to fire or sufficient heat, the foil covering will peel away from the middle layer of tar
impregnated paper. The paper will give off flammable gases that rise and build
up between the insulation paper and plywood decking. When the ignition
temperature of the gases is reached, the gases will flash, resulting in heavy
char to the surrounding wood and burning insulation paper dropping to the
floor below (which contributes to rapid spread of the fire). Fire is then able to
expose the 2 x 4 inch joists and ½ inch plywood decking which offer little resistance
to fire.
If lightweight trusses are utilized for the purlins, consider additional and rapid failure
when the roof is exposed to fire.
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Open Web Bar Joist Roof/Parallel Truss
Figure 23. Open Web/Parallel Truss
Open web bar joist construction utilizes a popular building material (metal) in a wide
variety of buildings, large and small. Top and bottom chords are usually made from
1/8 inch steel and web supports are solid 5/8 inch steel bar. Large buildings may
have bar-joists used as girders spaced up to 45 feet. Joists are spaced eight feet
apart to accept corrugated metal decking covered by alternating layers of tar and
tar paper.
These layers may also include a composition board or other type of material to
provide insulation protection. Additionally, 4 x 8 foot sheets of ½ inch plywood with
2 x 4 inch joists are gaining popularity. This roof may have composition covering
the decking.
Figure 24. Open Web/Parallel Truss
Strengths
Consider the perimeter of the building a strong area.
Hazards
Metal exposed to fire or sufficient heat (steel begins to lose its strength at 1000
degrees F) will expand, twist and possibly fail. Therefore, when the entire roof is
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comprised of metal, the short time necessary for roof collapse should be a major
concern.
Lightweight Concrete Roof (Non-Structural)
A steel or wood sub-structure is covered by corrugated metal ("Robertson
Decking"). An air-entrained mixture of sand, cement and, occasionally, pea gravel
is pumped on top of the corrugated metal decking and 4 x 4 inch or 6 x 6 inch wire
mesh to a thickness of three to four inches. Composition roofing material makes
up the final layer. These roofs are utilized when additional insulative properties are
desired (next to airports, freeways, etc.).
Figure 25. Lightweight Concrete Roof
Strengths
Lightweight concrete roofs offer a strong, hard surface. They are structurally sound
and resistant to fire.
Hazards
Concrete roofs are difficult to penetrate with a chain saw or rotary saw with a
masonry blade. Use a rotary saw with a diamond blade or carbide tipped wood
blade to cut ventilation openings.
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METAL CONSTRUCTION METHODS
Buildings that are primarily constructed of metal can be categorized as follows:
Corrugated
These buildings utilize a sub-structure of wood or steel, covered with corrugated
steel, aluminum or fiberglass. They are easily erected, can be utilized in various
types of applications, and are easily identified by their characteristic "corrugated"
appearance.
Figure 26. Corrugated Metal Roof
Hazards
The corrugated portions of these buildings will quickly fail when subjected to
sufficient heat or fire. Remember, steel loses its tensile strength at 1000 degrees
F, and aluminum or fiberglass offers little resistance to fire. Roof ventilation
operations on these buildings should be considered extremely dangerous.
Metal Beam
These buildings have a sub-structure of steel beams, usually coated with a sprayed
on fire retardant material. This skeleton is then finished with an exterior of concrete,
masonry, glass or similar materials.
This type of building will vary from two stories to the tallest high rise. Modern High
Rise buildings and multi-story office buildings typify this type of building. Although
structurally strong, consideration must be given to the type of fire, intensity of fire,
and the type of building materials exposed to fire.
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Figure 27. Metal Beam Structural Members
Hazards
Vertical extension of fire and smoke to upper floors is enhanced in buildings with
multiple floors.
Falling panels of glass or other building materials.
What you see is "not what you get." Brick buildings that consist of brick construction
offer both structural integrity and the lack of vertical extension through the walls.
However, newer buildings that appear to be of brick construction covered with brick
veneer attached to lightweight construction. Pre-fire planning your area and being
familiar with construction and specific buildings is the key.
When exposed to sufficient heat, metal beams can expand 9" per 100' which can
push out walls, etc.
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CONCRETE CONSTRUCTION METHODS
Tilt Up
These buildings are made of concrete slabs that have been "tilted up" into place to
form exterior walls of a structure. These buildings are easily identified by their
exterior appearance and can be up to five stories in height.
Figure 28. Tilt-Up Building Construction
Hazards
Expect to find lightweight construction in the interior walls, floors (if multiple story)
and roof. Lightweight roof construction may be comprised of 2-in x 4-in or 2-in x 3-
in in tension and compression and extensive use of ½ inch plywood. These
contribute to rapid spread of fire and early roof collapse. Ventilation operations
on this type of roof are dangerous unless personnel are properly trained.
The modern "tilt up" with its characteristic flat roof has increased the popularity of
the facade. The style of construction allows increased areas of fire spread and
collapse potential that may threaten personnel close to the exterior of a structure.
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MASONRY CONSTRUCTION METHODS
Buildings that have masonry as the prime material can be categorized as follows:
BRICK
One of the more popular building materials used in various types of buildings, old
and new, is the common brick. Unfortunately, brick buildings that were constructed
prior to the 1930's are significantly different, both in appearance and structural
integrity than brick buildings built today. It is safe to assume that the masonry
portion of brick buildings constructed before the 1930's are "an accident looking for
a place to happen," while the masonry portion of brick buildings built after the 1930's
are very stable and are constructed as follows:
Pre-1933
Brick buildings constructed up until the 1930's are commonly classified as
unreinforced masonry buildings. These buildings, built prior to 1933, are of
ordinary brick construction and present extreme hazards to firefighting personnel
under fire or earthquake conditions. Masonry buildings constructed prior to 1933
have the following characteristics.
Figure 29. Unreinforced masonry building
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Figure 30. Rafter Tie Plate in Pre-1933 Masonry Brick
Construction. Also shown King Rows.
Mortar consisting of sand and lime only, no cement.
Lack of steel reinforcing rods ("rebar").
Brick exterior walls about 13 inches thick.
Parapet walls around the perimeter of a roof. Parapet walls can be three
feet above the roof line, and five feet or more if used as a facade on the front
of a building.
Floor and roof joists that are "let" (penetrated or resting in a cavity) into the
inside of the exterior walls.
Straight roof sheathing.
Roof and floor joists that are "fire cut" (ends were cut with an angle) so they
would pull loose from the exterior walls during a fire and collapse into the
interior of the building without pulling down the exterior walls.
Post 1933
After the disastrous Long Beach Earthquake of 1933, building codes were revised
to provide better earthquake safety for new masonry buildings. The following
revisions characterize the masonry buildings that were built after 1933:
Exterior walls are required to be at least nine inches thick.
Masonry walls are required to be reinforced with steel "rebar".
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All joists and rafters are required to be anchored to exterior walls. This is
usually accomplished by bolting a "ledger board" to a masonry wall and
attaching the joist and rafters to the ledger board with metal hangers.
Cement utilized in the mortar.
Diagonal roof sheathing.
Post 1959
After the Tehachapi Earthquake of 1959, building codes were modified to require
the following retroactive correction on existing buildings masonry construction:
A four to six inch concrete bond-beam cap to be laid on top of lowered
parapet walls along public ways and exits.
Parapet walls should not be higher than 16 inches including the bond-beam
cap.
Exterior walls drilled at the roof rafter level and a steel anchor bar/rod
installed every four feet and attached to the existing roof rafter. This
modification rendered the fire cut of the roof rafter ineffective. The steel
anchor bar/rods are secured to the exterior of the building by a plate/nut
combination that is known as "rafter tie plates".
Figure 31. Post 1959 Masonry Construction Rafter Tie Plate
Post 1971
The Sylmar Earthquake of 1971 provided the impetus to further modify existing
buildings of unreinforced masonry construction. A Committee was formed to
evaluate these buildings and review current building codes. That review was
instrumental in additional retroactive corrections (EARTHQUAKE ORDINANCE)
designed to prevent exterior walls from collapsing outward by stabilizing the building
by:
Anchoring walls to floor and roof systems.
Strengthening roof construction (plywood, metal straps, etc.)
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Brick Identification
Unreinforced masonry buildings will share all or a portion of the following
trademarks:
Rafter tie-plates on the exterior of a building (rafter tie-plates can be found
on remodeled "new" appearing buildings). These exterior plates on a
masonry building indicate that the joists and rafters of the building are
anchored to the exterior walls.
A bond-beam cap of concrete on top of parapet walls. Concrete bond-beams
may also have been added for strength over the windows and between the
second floors of multi-story buildings. This is a common technique used for
additional strength for exterior walls.
Deeply recessed window frames. Window frames are "set" to the inside of
the wall, thereby exposing about eight-inches of brick return on the exterior
of a building. Remember, these walls are at least 13 inches thick.
Windows may have arched or straight lintels.
Figure 32. Masonry Window Lintel
The lime mortar between the bricks is white, porous, sandy, and may be
easily rubbed away by a fingernail, knife, etc. In some cases, the bricks have
not been uniformly laid and the workmanship appears sloppy.
In every fourth to seventh row of bricks, one row will have been laid "on-end."
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This row of bricks is referred to as the "king row" and is for additional
strength.
Figure 33. Brick Masonry King Row
Some unreinforced masonry buildings have a fancy or better quality brick on the
front of the building to improve the appearance. However, utilizing the preceding
trademarks, the following indicators can be easily identified:
Recessed windows
Bond-beams over the windows
Rafter tie plates
Additionally unreinforced masonry buildings are required to be reinforced to comply
with the Earthquake Ordinance. Modifications may include the following:
Add steel bracing from parapet walls to roof structural members.
Figure 34. Steel Bracing Added to Parapet Walls
Metal straps across the width of the roof and attached to opposing walls. The straps
are usually 1/3 of the length of the building back from the front and rear walls.
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Remove the layers of composition and cover the sheathing with ½ inch plywood.
This decking is then recovered with composition.
Hazards
The primary hazards of this type of construction are as follows:
Wall, roof, and floor collapse. Unreinforced masonry construction that is held
together with lime, mortar, and sand creates a weak wall; particularly after the lime
mortar has deteriorated with age and/or is subjected to heat from a fire. These
buildings were originally designed so that floor and roof joists would pull out from
the walls during a fire, thereby preventing wall collapse. When rafters or joists are
anchored to the walls, collapse is enhanced during fire conditions.
An additional collapse hazard can result from arch type roofs (bowstring, tied
truss and lamella) on unreinforced masonry construction. When arch roofs
(particularly the bowstring and tied truss) are modified as per the Earthquake
Ordinance, the additional roof stability provided by plywood and metal straps can
increase the potential for collapse of front/rear walls.
A collapsing truss that is connected to the "HIP" rafters at the ends of these
buildings will push the hip rafter outward , also pushing the corresponding wall
outward with considerable force.
Considerations
Personnel and apparatus placement. Due to the presence of arch roofs that have
been modified as per the Earthquake Ordinance and floor/joists rafters that have
been anchored to the walls, exterior walls may suddenly collapse (during fire
conditions) outward a distance that is equal to at least the height of the wall. The
primary danger from collapse is the front and rear walls of a building. The
secondary danger from collapse is the side walls of a building. The safe areas are
as follows:
1. The corners of a building.
2. A distance at least equal to the height of the walls away from a building.
Placement of personnel and apparatus should be a primary concern when
confronted with this type of construction.
During retrofit modifications, consider:
Vertical openings.
Holes in floors and ceilings.
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Building materials in hallways.
Stairs removed.
Metal straps across the width of the building and three to four feet from walls
are hard on power saws.
Decking comprised of sheathing, plywood, and composition. The extra
"thickness" of the decking will not enhance "feeling" the rafters with a power
saw.
Block
These buildings are primarily concrete block that form the exterior walls. This type
of construction is strong and extensively utilized.
Hazards
It is common to find this type of construction supporting lightweight floor joists and
roofs (depending on the age of the building). Facades are also common on this
type of construction.
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FRAME / STUCCO CONSTRUCTION METHODS
These buildings are used in a wide variety of applications, old and new. Although
they are structurally sound, the stucco exterior walls can support extensive remodel
additions and/or conventional or lightweight construction. The difference in
construction can be detected by a prior knowledge of the building (pre-planning) or
recognizing the difference between an "old or new" style of building.
Figure 35. Frame Construction and Fire Blocks
Hazards
Vertical spread of fire through the walls is a possibility (if balloon construction
is present). However, this is controlled by horizontal fire blocking if present.
Lightweight construction. The age of the building is a key factor in
identification of this construction.
Facades
A facade can be defined as an "identifiable style of construction on the exterior of a
building that will conceal and spread the travel (extension) of fire." To summarize,
facades are external attics.
Style
Currently, this style of construction is enjoying widespread popularity across the
country. Facades are utilized to conceal equipment and machinery on flat roofs.
As the popularity, utilization, and complexity of the facade increases, so does its
impact on firefighting operations.
The following four areas should be considered when confronted by this
construction:
Overhang
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Consider the distance a facade extends from the building (A). As the size or
extension from the building increases, so should concern about structural stability
when a facade is exposed to fire. As the size of a facades increases, so does its
complexity and the materials utilized in this construction. The size of a facade will
have a direct effect on the area (what there is to burn) and the path and travel
(extension) of a fire. Additionally, the extension of fire will be affected by the
presence or lack of "fire stops."
Figure 36. Large Facade with Overhang
Facades are usually open or common to the attic of a building. This is common
along with a lack of fire stops in the facade. Unless proven otherwise, expect any
facade to be not fire-stopped and open to the attic of the building. Additionally, if a
facade is exposed to fire, expect the facade to collapse outward at least the
distance of the overhang of the facade.
Figure 37. Facade without Fire Stops, notice the uninhibited
fire travel.
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Figure 38. If Facade is involved with fire, ensure that the
entire facade is opened up to check for fire extension and
stop fire travel.
Facade Height
Facade height (B) and shape will affect stability, the amount of building material
utilized, and the potential path of fire. Two additional areas to consider are roof line
and laddering operations.
On buildings without facades, roofs such as sawtooth, arches, etc. can be observed
from the ground. This is helpful (and often necessary) when laddering a building
and when considering roof ventilation operations. Consider what effect a facade
will have on ground operations.
Supported or Unsupported
The structural stability of a facade will be enhanced if supported (C) by pillars, posts
or other means that are often used for style of decoration.
Height from the roof
When confronted by a facade, an area that is often neglected is the distance from
the facade to the actual roof line. Facades normally hide or conceal the roof line.
Perimeter
Facades are usually constructed on the portion of the building that is seen as the
building is normally approached (the front and part of the sides). It requires extra
money to construct a facade around the sides and back of a building. If possible,
consider laddering that portion of the building without a facade. A good size-up for
ladder placement is mandatory.
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Scuppers
Roofs that are lower than a facade utilize scuppers for drainage. The scupper is
the actual roof line.
Figure 39. Scuppers with Parapet Wall
Attic Vents
Roof lines are between the attic vent and top of the facade or parapet.
Equipment on the Roof
Equipment that can be seen above a facade will indicate the roof is in close
proximity.
Windows
Roof lines are between the top of windows and the top of the facade or parapet.
Rafter tie plates
Rafter-tie-plates will indicate the location of roof rafters and will identify the roof line.
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BUNGALOW AND BALLOON CONSTRUCTION
These buildings were constructed during the 1920's, 1930's and 1940's, and are
primarily utilized in single family dwellings and multi-story habitational occupancies
up to four stories.
Hazards
Increased exposure problems due to all-wood construction.
Bungalow Construction
"Rough-cut" 2 x 4 inch studs and rafters were commonly utilized during the
construction of these structures. Of particular interest was the utilization of 2 x 3 or
2 x 4 inch rafters for roof structural members and a ridge that is comprised of a 1 x
6 inch ridge board (the 2 x 4 inch rafters are butted together). This type of
construction can be classified as an "old type" of lightweight construction.
Additionally, due to the age of these buildings, the presence of termites, multiple
layers of composition on the roof, and various types of remodels will affect the
structural stability of this type of construction.
Balloon Construction. Although these buildings can be considered structurally
sound, they often hide "balloon construction" which does not utilize horizontal fire
blocking in the walls and plates between multiple floors separating the attic from
open vertical runs in the walls. Platform construction utilizes fire blocking in the wall
(studs which eliminate open vertical pathways to the attic). Balloon construction
will quickly assist the travel of fire up the walls and into the attic, creating additional
considerations.
Figure 40. Balloon Frame
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Figure 41. Platform Frame
Knob and Tube Wiring. Prior to the use of conduit and romex, a pair of wires were
run throughout a structure to provide electricity to the various rooms. These wires
are suspended on ceramic insulators and pass through ceramic tubes when it is
necessary to run the wires through studs or plates.
Due to the age of this type of construction, the insulation has hardened, become
brittle, and in many cases has fallen from the wires, leaving the wires exposed which
presents an obvious electrical hazard to personnel opening walls or ceilings during
fire suppression operations. When this type of construction exists, particular
emphasis must be placed on eliminating the electrical "service" to the involved
structure.
Figure 42. Knob and Tube Wiring
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CURTAIN CONSTRUCTION METHODS
This method has dramatically cut the time necessary to complete the multi-story
and high-rise buildings by bolting pre-fabricated panels on the exterior of buildings.
Generally, a skeleton is constructed of steel beams. Pre-fabricated panels made
from materials such as lightweight concrete, slate, granite, fiberglass, glass panels,
etc., are bolted into place utilizing metal brackets on the panels that mate to metal
brackets on the steel beams of the building. These panels can also be bolted to
sheet metal or aluminum outriggers/struts that are attached to the steel beams.
Once the decorative panels have been installed, glass panels or windows are
installed to complete the exterior of the building. Once the exterior of the building
is completed, the interior can be completed without interference from the weather.
Depending on the particular method that is employed, "curtain" construction can be
about 60% faster than conventional construction.
Figure 43. Curtain Construction Glass Opening
Hazards
Steel exposed to fire or sufficient heat begins to lose its structural integrity at 1000
degrees F. Aluminum exposed to the same conditions will lose its tensile
strength and possibly fail in a shorter time period. Because exterior panels are
structurally dependent on metal brackets or struts, expect exterior panel failure
when this type of construction is exposed to fire.
Large glass panels have replaced conventional windows. Glass panels can also
be expected to fail when exposed to fire or sufficient heat.
Identification
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Identification of this type of construction is facilitated by:
Pre-fire planning.
Recognizing the "cube" or "smooth" look.
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AGE OF THE BUILDING
When approaching any buildings, consider its AGE. What is the building telling you
about its construction? Is it lightweight construction or masonry with unreinforced
walls? Three general time periods that can be used to classify buildings as follows:
Pre-1933
Structures built during this time period are characterized by the following:
Unreinforced masonry. Roofs on these buildings are constructed using
conventional methods. However, the brick walls are inclined towards sudden
and early collapse if exposed to significant fire.
Structures that utilize the wood shiplap exterior, balloon and bungalow
construction and knob and tube wiring.
Straight or diagonal roof sheathing.
1933 to Late 1950's
Expect to find buildings with solid construction and in compliance with
building codes.
Straight or diagonal sheathing.
1950's to Present
New style buildings with concrete-tilt up walls, facades, and flat roofs indicate
that lightweight construction may be present.
With a basic knowledge and familiarity of construction, roof styles, construction
methods, and the age of the building, a foundation will be laid to assist in developing
a structure size-up that assists in effective ventilation operations and enhances
safety. Additionally, fireground operations, communications, and resource
deployment will be improved.
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IMPACT OF LIGHTWEIGHT
CONSTRUCTION ON FIREGROUND DECISIONS
The implementation of lightweight construction within the building industry has
resulted in a significant impact on fireground decisions when personnel are
confronted with a structure fire that utilizes lightweight construction.
To ensure effective and safe fireground operations, personnel must address four
areas:
Identification
The presence of lightweight construction must be identified.
This is accomplished by pre-fire planning, familiarity with a district, recognizing the
style and age of a building, and proper communications between fireground
personnel.
Communication
There must be a flow of information between incident commanders, company
commanders, and other personnel that may be affected by a particular type of
construction.
Time
Construction size and configuration directly effects fireground time. It is imperative
to determine how much time is left to ensure the safety of an intended operation
and selecting an appropriate method or operation to safely accomplish a task.
Operations
When the preceding factors are evaluated, a foundation will be formulated to
determine the appropriate and safe implementation of interior, exterior, offensive,
or defensive operations.
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DEFINITIONS
Fire Cut - ends cut into an angle to allow the joist to fall into the structure in the
event of a fire to prevent wall collapse.
Ledger Board - A narrow horizontal board to attach a row of studs to support the
ends of a floor or ceiling joists.
Let - Joist is penetrated into or resting in a cavity of exterior walls.
Parapet Wall - A parapet is a barrier that is an extension of the wall at the edge of
a roof, terrace, balcony, walkway or other structure
Petrochemical - Relating to or denoting substances obtained by the refining and
processing of petroleum or natural gas. In building construction, the presences of
gasoline type substances.
Rafter Tie Plate - steel anchor bar/rods are secured to the exterior of the building
by a plate/nut combination
Size Up - a mental evaluation that assists in determining a course of action and
methods necessary to accomplish a desired goal.
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REFERENCES
Standard Operating Procedures:
Section 202.002b, Residential Structures, Garage
Section 202.003, Commercial/Big Box
Section 202.023a, Center Hall Construction
Section 202.024, 1-2 Family Residential Structures
Guides:
High Rise Guide