7 FireResistive Construction 2nd part

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Session 14 Codes Ermal Shpuza
7 Fire-Resistive Construction (2nd
part)
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Fire Barriers
Fire barriers FB are similar to FW but with
simpler criteria. They are used to separate
vertical exit enclosures from other egress
components, to separate different occupancies, or
to divide a single occupancy into different fire
areas. FB serve to separate vertical exit
enclosures from other egress components.
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Fire Barriers
FB serve to set apart different occupancies, or
divide a single occupancy into different fire
areas. Walls located on the outside of the
building at rated enclosure may have a different
rating than the walls facing the interior of the
building. Exterior wall ratings are determined by
exterior criteria according to 704 as well as
exit requirements of 1005.3.4
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Fire Barriers
FB are to be continuous between floor levels and
extend to abut adjacent interior or exterior
walls. The intent is that the FB prevent the
spread of smoke or fire for the duration of the
time rating. Penetrations and openings are
permitted but must be protected to maintain the
integrity of the FB. FB should extend from the
top of the floor assembly below to the underside
of the floor or roof deck or slab above. FB
should be continuous through concealed ceiling
spaces. Supporting floor should have the same
fire rating as the fire barrier supported.
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Shaft and Vertical Exit Enclosures
707.2 states that all openings through
floor/ceiling or roof/ceiling assemblies will be
protected. Shaft enclosures differ from FB in
that they typically enclose shaft extending
through several floors. The required rating for
shafts is usually determined by the number of
floors they interconnect. Shafts should be of
2-hr rating if extending four stories or more and
1-hr otherwise. Shaft ratings are equal to those
of the floor assemblies but need not be
gt2hr. Vertical spaces within shaft enclosures
should be fire-blocked at each floor level.
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Shaft and Vertical Exit Enclosures Exceptions
to 707.2
1 - Openings in residential units extending less
than 4 stories need not be enclosed. 2 -
Escalators and stairs not used as means of egress
need not be enclosed in fully sprinklered
buildings with a draft curtain around the floor
opening. This exception applies for lt 4 stories
except Group B and M where there is no height
limitation. The opening dimension should not
exceed twice the size of the escalators or
stairs. For cases with power-operated shutters
with 1.5 hr ratings, there is no limit for the
number of floors that can be penetrated. 3 -
Pipe, vent or conduit penetrations protected at
the floor or ceiling according to 711.4 need not
be protected. 4 Ducts protected as per 711.4
also need not be protected.
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Shaft and Vertical Exit Enclosures Exceptions
to 707.2
5 Floor openings in buildings considered as
covered malls or atria need not have shaft
protection, however, these occupancies require
meeting many other specific fire protection
requirements. 6 Chimneys need not be in a
shaft, but concealed spaces should be blocked.
7 Openings that do not connect more than 2
stories and that are not part of a means of
egress may be open, even in buildings not
equipped with fire-sprinklers 8 Ramps for
automobiles in parking garages may be open when
the criteria of 406.3 and 406.4 for open or
enclosed parking garages are met. 9 openings
connecting mezzanines and the floor below need
not be enclosed. 10 Expansions or other joints
need not be enclosed, but they should be
protected as per 712.
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Shaft and Vertical Exit Enclosures
Shafts must be fully contained. In cases when a
shaft does not fully extend to the floor above or
below, it must be enclosed at the top or the
bottom. These enclosures may be of the same
fire-rating as the the last floor penetrated but
not less than the rating of the shaft.
Shafts may terminate in a room related to
the purpose of the shaft, which must be enclosed
by the same construction and with the same
rating.
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Shaft and Vertical Exit Enclosures Laundry
Chutes
Refuse and laundry chutes need be separated from
the rest of the building with 1-hr rated access
rooms on each floor and with 1-hr termination
rooms at the bottom of the shaft according to
707.13. Active fire protection is also required
as per 903.2.12.2
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Shaft and Vertical Exit Enclosures - Elevators
While 707.14 requires that elevator shafts be
built as other shafts, it adds requirements for
elevator lobbies at fire-rating as corridors
according to 1004.3.2.1. The lobbies are to be
constructed as for other fire barriers with
opening protectives and a means of egress.
Elevator lobbies are required where an elevator
opens onto an exit access corridor. The
exceptions to the elevator lobby requirements
are 1 For office buildings, when the building
lobby level is sprinklered, the street-level
lobby may be open without elevator lobby
enclosures. 2 where shafts are otherwise not
required per the exceptions to 707.2 3 Doors
that enclose elevator shaft for sealing off the
shaft from smoke and fire may be substituted for
lobbies when they comply with 3002.6 4 Lobbies
may be omitted for up to 3 stories above the
lowest level of fire-department access.
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Fire Partitions
Fire partitions FP are the next level of
fire-resistive wall construction below the FW and
FB. They typically have 1-hr fire-resistance
ratings and are primarily used for separation
between dwelling units and guest rooms 310.3
for separation of tenants in a covered shopping
mall 402.7.2 and for exit corridors
1004.3.2. FP have similar relationship to
exterior walls as FW and FB. They also have
similar requirements for penetrations, openings
and ductwork as for other groups of partition
types. While FP are to extend to the structure
above and below, there are exceptions contained
in 402.7.2.
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Fire Partitions - Exceptions
1 When the floor is 1-hr rated, the partition
need not extend into the crawl space below. 2
When the room-side fire-rated membrane of a
corridor extends to a fire-resistive floor or
ceiling above, the corridor ceiling may be
protected, as for a 1-hr rated floor/ceiling
assembly. 3 When the walls and ceiling form
a tunnel, the fire rating need not extend above
the top of the ceiling assembly.
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Fire Partitions - Exceptions
4 In covered mall buildings, as defined in
402.7.2 , fire-rated assemblies need not extend
above the ceiling line of the tenant spaces. The
ceilings are not required to be rated in such
conditions. 5 The fire barrier forming the
separation between dwelling units in Group R-2
occupancies need not extend into the attic is
draft-stopped at every 3,000 sf or every 2 units,
whichever is the smaller. 6 If combustible
floor/ceiling or roof/ceiling spaces are
sprinklered, fire-blocking or draft-stopping will
not be required.
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Smoke Barriers
709 treats smoke barriers as FB, but with
emphasis upon restricting the spread of smoke.
Smoke barriers SB are required to have a 1-hr
rating with 20-minute-rated opening protectives.
SB need not be continuous through concealed
spaces unless they touch assemblies that will
resist the passage of smoke, such as walls
meeting fire-rated ceiling assemblies.
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Horizontal Assemblies
710 defines horizontal assemblies HA as
floor/ceiling assemblies and roof/ceiling
assemblies that require a fire rating. The rating
is determined based on construction as dictated
by Table 601. When separating occupancies or
dividing a single occupancy into fire areas, the
rating of the HA must also be examined against
the requirements of Table 302.3.3 710.3.2
permits lower membranes to be omitted over
unusable crawl spaces and upper membranes to be
omitted below unusable attic spaces in 1-hr rated
floor constructions. Unprotected skylight
openings are allowed when separation requirements
to adjacent structures are met according to
704.10 and the integrity of the roof
construction around the skylight opening is
maintained as for the rest of the roof. Any
structural members or walls supporting a
horizontal assembly must have at least the same
fire-resistance rating as the horizontal assembly.
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Penetrations
711 requires that penetrations be protected to
maintain the fire-resistive integrity of the
assembly being penetrated. Penetration treatment
requirements are based on the size and quantity
of penetrations. Exceptions allow for certain
small pipes or electrical components of specified
sizes. Penetrations are of two basic types. One
is a through penetration that passes through an
entire assembly. The other is a membrane
penetration that goes through only a portion of
an assembly.
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Penetrations
Sleeves must be fastened to the assembly
penetrated Any space between the sleeve and the
penetrating item, and between the sleeve and the
assembly penetrated must be protected by an
approved fire-stop material or system Fire-stop
system for through penetrations must have an F
rating at least equal to the fire rating of the
assembly penetrated. Concrete grout or mortar
may be permitted to act as a fire-stop around
penetrating items through concrete or masonry
walls.
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Penetrations
711.3.2 limits the size of steel electrical
boxes and requires that they be separated by a
horizontal distance of not less that 24, or by a
horizontal distance not less than the depth of
the wall cavity filled blocking.
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Penetrations
Horizontal Assemblies The criteria are more
stringent given the probability of spread of
smoke by convective forces. Ducts are required to
be treated as penetrations and the spaces around
to be sealed. Recessed lighting fixtures shall
not reduce the rating of floor/ceiling assemblies
that are required to have a minimum of 1 hr
rating.
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Penetrations
The space around a noncombustible item that
penetrates only a single rated floor need only be
filled with an approved material The
noncombustible item may penetrate multiple rated
floors if limited in size according to 711.4.1
711.4.3 requires that even non-rated horizontal
assemblies have spaces filled to resist the free
passage of smoke and flame. In this case
penetrating items may connect no more than 2
stories. Noncombustible items may penetrate no
more than 3 stories.
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Joint Systems
Expansion, seismic movement and construction
control joints are treated in a similar manner to
penetrations, 712 The goal is to maintain the
fire-resistive capabilities of horizontal and
vertical assemblies where joints occur. Joints in
rated assemblies are to be fire tested to match
the assembly rating before and after
movement. Expansion joints are to have
fire-resistance as for other penetrations.
Joints at the intersection of floor assemblies
and exterior curtain walls are included in
712.4. These intersections are to be sealed with
approved materials.
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Fire-Resistance of Structural Members
713 requires that the ratings of structural
members comply with the requirements for the
types of construction set forth in Table
601. 713.2.1 requires individual structural
members to be fully protected on all sides for
their entire length in case they are required to
be rated and either support direct load from more
than 2 floors or a floor and a roof, or support a
load bearing wall or a non-load bearing wall more
than two stories in height.