BUILDING CLASSIFICATION Lieutenant Larry Booth Memphis Fire Department 2007

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15 Νοε 2013 (πριν από 3 χρόνια και 9 μήνες)

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BUILDING CLASSIFICATION

Lieutenant Larry Booth

Memphis Fire Department

2007



Buildings are broken down into 5 major classifications based mainly on the construction
materials used to support the load of the building. Other factors such as sprinkler syste
ms,
stairwells, and non load bearing interior walls factor into local codes but for our purposes
we are looking at the major load bearing components of the building to determine the
classification. These components are:



Beams
are members that carry loads
perpendicular to their longitudinal
dimension. A wooden floor joist is an example of a beam.



Columns

are members that are designed to carry the load axially. Columns can
be used to support a beam and transmit the load to the ground.



Arches

are basically
curved beams that are used support roofs and on bridges.



Trusses
are framed structural units made of gr
oups of triangles in one plane.

Trusses serve the same function as beams, but are light weight and can span great
distances.



Load bearing walls

perform
the same function as columns but are walls. They
are subdivided as interior and exterior. Interior load bearing walls are placed
inside the building such as a central elevator core. External load bearing walls are
just that, external walls that carry th
e load of the building to the ground. Not all
interior or exterior walls are load bearing. To tell the difference look for a wall
that supports a beam or a truss. This will be your load bearing wall.



Floors

transmit the load to beams or trusses and make

up the usable space of the
building.



Roof

provides
protection for the interior space of the building. Roofs are
supported by beams trusses and arches.


These classifications, and using them correctly during size up, are important because they
describe ho
w the building will hold up under fire conditions and give the officers an idea
of how safe the building will be during fire fighting operations.



FIRE RESISTIVE (TYPE I)


The structural members are of noncombustible materials that have a specified fire
r
esistance rating. These ratings are based on NFPA 220 and The Uniform Building
Code
tm
. The “Fire Resistive Classification” is further broken down into sub
-
classifications that reflect the hour ratings for each of the primary structural members
.

Generall
y this hour rating for load bearing members is 3
-
4 hours (including roof trusses,

and

beams), and 11/2
-
2 hours for the actual roof material itself.

Floor material is rated
from 2
-
3 hours.


For our purposes the
identifying

factors are the
main structural m
embers. Steel

and
reinforced concrete are the most common ma
terials used. Although steel is

noncombustible it
rapidly looses strength when attacked by fire. For structural steel to be
considered “Fire Resistive” construction it must have some type of in
sulation material,
usually a sprayed on coating. Concrete is also a noncombustible material with excellent
insulating properties, but to be considered “Fire Resistive” it must be reinforced with
steel rebar.


What to look for:
Insulated

steel and/or

rein
forced concrete load bearing components.



NONCOMBUSTIBLE (TYPE II)


The structural members are of a noncombustible material but have no fire resistance. The
use of unprotected steel is generally the defining characteristic of a Type II building.
Other

noncombustible materials besides concrete and steel are also common in Type II
buildings. For example
;

concrete block (cinder block) exterior walls with unprotected
steel beams or trusses for roof support is common.
Also common is the use of steel
beams

and
columns

to support the load of the building with block non load bearing
exterior walls or a sheet steel metal exterior wall attached to the columns. (The new
USAR warehouse out at training is a good example of this.)


What to look for:

Unprotected

st
eel beams trusses and columns, with noncombustible
walls of concrete, brick/ block or sheet metal.


ORDINARY (TYPE III)


Ordinary construction covers a wide variety of buildings but it’s defining feature is that
the exterior load bearing walls are of mason
ry and some or all other structural
components are combustible ie wood. The masonry walls can be brick, stone, concrete
block, terra cotta tile, adobe or cast in place concrete. Inside you will find wood floor
and ceiling joists and possibly wood floorin
g. When we think of ordinary construction
we think of the old brick buildings down on main street, but modern day use of this type
of construction is evident in every FMZ. Your local McDonalds is probably concrete
block load bearing walls with a wood tru
ss roof. This is ordinary construction.


What to look for:

Masonry exterior load bearing walls with
other wood load bearing
components.


HEAVY TIMBER (TYPE IV)


Also called Mill Construction, Type IV buildings are the same as Type III except that the
woo
d beams and columns are massive. The floors are generally also made of hardwood.


What to look for:
Masonry exterior load bearing walls with massive solid or laminated
wood load bearing components and wood floors.




WOOD FRAME (TYPE V)


All major struc
tural components are permitted to be of combustible material. Thus the
term wood frame. There is generally some fire resistance based on the use of gypsum
board (sheet rock) and in the NFIRS system this is referred to as protected wood frame.


Wood frame

is used in residential and commercial buildings. Note:

The presence of a
non load bearing brick outer wall does not change the classification of the building.
A single family house with brick exterior walls is still a wood frame house, not
ordinary cons
truction or a brick house or a brick frame house. THIS IS A WOOD
FRAME HOUSE.


What to look for:
Wood load bearing walls, wood beams or trusses throughout.