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SECTION 717 CONCEALED SPACES
717.1 General. Fireblocking
and draftstopping shall be installed in combustible concealed
locations in accordance with this section. Fireblocking shall
comply with Section 717.2. Draftstopping in floor/ceiling
spaces and attic spaces shall comply with Sections 717.3 and
717.4, respectively. The permitted use of combustible materials
in concealed spaces of I buildings of Type I or II construction
shall be limited to the applications indicated in Section
717.5.
717.2
Fireblocking. In combustible construction, fireblocking
shall be installed to cut off concealed draft openings (both
vertical and horizontal) and shall form an effective barrier
between floors, between a top story and a roof or attic space.
Fireblocking shall be installed in the locations specified
in Sections 717.2.2 through 717.2.7.
717.2.1
Fireblocking materials. Fireblocking shall consist of
2-inch (51 mm) nominal lumber or two thicknesses of 1-inch
(25 mm) nominal lumber with broken lap joints or one thickness
of 0.7I9-inch (18.3 mm) wood structural panel with joints
backed by 0.7I9-inch (18.3 mm) wood structural panel or
one thickness of 0.75-inch (19 mm) particleboard with joints
backed by 0.75-inch (19 mm) particleboard. Gypsum board,
cement fiber board, batts or blankets of mineral wool, glass
fiber or other approved materials installed in such a manner
as to be securely retained in place shall be permitted as
an acceptable fireblock. Batts or blankets of mineral or
glass fiber or other approved nonrigid materials shall be
permitted for compliance with the lO-foot (3048 mm) horizontal
fireblocking in walls constructed using parallel rows of
studs or staggered studs. Loose-fill insulation material
shall not be used as a fireblock unless specifically tested
in the form and manner intended for use to demonstrate its
ability to remain in place and to retard the spread of fire
and hot gases. The integrity of fireblocks shall be maintained.
717.2.1.1
Double stud walls. Batts or blankets of mineral or
glass fiber or other approved nonrigid materials shall
be allowed as fireblocking in walls constructed using
parallel rows of studs or staggered studs.
717.2.2
Concealed wall spaces. Fireblocking shall be provided
in concealed spaces of stud walls and partitions, including
furred spaces, and parallel rows of studs or staggered studs,
as follows:
1.Vertically at the ceiling
and floor levels.
2. Horizontally at intervals
not exceeding 10 feet (3048 mm).
717.2.3
Connections between horizontal and vertical spaces. Fireblocking
shall be provided at interconnections between concealed
vertical stud wall or partition spaces and concealed horizontal
spaces created by an assembly of floor joists or trusses,
and between concealed vertical and horizontal spaces such
as occur at soffits, drop ceilings, cove ceilings and similar
locations.
717.2.4
Stairways. Fireblocking shall be provided in concealed
spaces between stair stringers at the top and bottom of
the run. Enclosed spaces under stairs shall also comply
with Section 1009.5.3.
717.2.5
Ceiling and floor openings. Where annular space protection
is provided in accordance with Exception 6 of Section
707.2, Exception 1 of Section
712.4.1.2, or Section 712.4.2,
fireblocking shall be installed at openings around vents,
pipes, ducts, chimneys and fireplaces at ceiling and floor
levels, with an approved material to resist the free passage
of flame and the products of combustion. Factory-built chimneys
and fireplaces shall be fireblocked in accordance with UL
103 and UL 127.
717.2.6
Architectural trim. Fireblocking shall be installed
within concealed spaces of exterior wall finish and other
exterior architectural elements where permitted to be of
combustible construction as specified in Section
1406 or where erected with combustible frames, at maximum
intervals of 20 feet (6096 mm), so that there will be no
open space exceeding 100 square feet (9.3 m2).
Where wood furring strips are used, they shall be of approved
wood of natural decay resistance or preservative-treated
wood. If noncontinuous, such elements shall have closed
ends, with at least 4 inches (102 mm) of separation between
sections.
Exceptions:
1.Fireblocking
of cornices is not required in single-family dwellings.
Fireblocking of cornices of a two-family dwelling is required
only at the line of dwelling unit separation.
2.Fireblocking
shall not be required where installed on noncombustible
framing and the face of the exterior wall finish exposed
to the concealed space is covered by one of the following
materials:
2.1.
Aluminum having a minimum thickness of 0.019 inch (0.5 mm).
2.2.
Corrosion-resistant steel having a base metal thickness
not less than 0.016 inch (0.4 mm) at any point.
2.3.
Other approved noncombustible materials.
717.2.7
Concealed sleeper spaces. Where wood sleepers are used
for laying wood flooring on masonry or concrete fire-resistance-rated
floors, the space between the floor slab and the underside
of the wood flooring shall be filled with an approved material
to resist the free passage of flame and products of combustion
or fireblocked in such a manner that there will be no open
spaces under the flooring that will exceed 100 square feet
(9.3 m'2) in area and such space shall be filled
solidly under permanent partitions so that there is no communication
under the flooring between adjoining rooms.
Exceptions:
1.Fireblocking
is not required for slab-on-grade floors in gymnasiums.
2.Fireblocking
is required only at the juncture of each alternate lane
and at the ends of each lane in a bowling facility.
717.3
Draftstopping in floors. In combustible construction,
drafts topping shall be installed to subdivide floor/ceiling
assemblies in the locations prescribed in Sections 717.3.2
through 717.3.3.
717.3.1
Draftstopping materials. Draftstopping materials shall
not be less than 0.5-inch (12.7 mm) gypsum board, 0.375-inch
(9.5 mm) wood structural panel, 0.375-inch (9.5 mm) particleboard,
1-Inch (25-mm) nominal lumber, cement fiberboard, batts
or blankets of mineral wool or glass fiber, or other approved
materials adequately supported. The integrity of draftstops
shall be maintained.
717.3.2
Groups R-l, R-2, R-3 and R-4. Draftstopping shall be
provided in floor/ceiling spaces in Group R-l buildings,
in Group R-2 buildings with three or more dwelling units,
in Group R - 3 buildings with two dwelling units and in
Group R-4 buildings. Draftstopping shall be located above
and in line with the dwelling unit and sleeping unit separations.
Exceptions:
1.Draftstopping
is not required in buildings equipped throughout with
an automatic sprinkler system in accordance with Section
903.3.1.1.
2.Draftstopping
is not required in buildings equipped throughout with
an automatic sprinkler system in accordance with Section
903.3.1.2, provided that automatic sprinklers are
also installed in the combustible concealed spaces.
717.3.3
Other groups. In other groups, drafts topping shall
be installed so that horizontal floor areas do not exceed
1,000 square feet (93 m2),
Exception:
Draftstopping is not required in buildings equipped throughout
with an automatic sprinkler system in accordance with Section
903.3.1.1.
717.4
Draftstopping in attics. In combustible construction,
drafts topping shall be installed to subdivide attic spaces
and concealed roof spaces in the locations prescribed in Sections
717.4.2 and 717 .4.3. Ventilation of concealed roof spaces
shall be maintained in accordance with Section
1203.2.
717.4.1
Draftstopping materials. Materials utilized for drafts
topping of attic spaces shall comply with Section 717.3.1.
717.4.1.1
Openings. Openings in the partitions shall be protected
by self-closing doors with automatic latches constructed
as required for the partitions.
717.4.2
Groups R-l and R-2. Draftstopping shall be provided
in attics, mansards, overhangs or other concealed roof spaces
of Group R - 2 buildings with three or more dwelling units
and in all Group R -1 buildings. Draftstopping shall be
installed above, and in line with, sleeping unit and dwelling
unit separation walls that do not extend to the underside
of the roof sheathing above.
Exceptions:
1.Where
corridor walls provide a sleeping unit or dwelling unit
separation, draftstopping shall only be required above
one of the corridor walls.
2.Draftstopping
is not required in buildings equipped throughout with
an automatic sprinkler system in accordance with Section
903.3.1.1.
3.In
occupancies in Group R-2 that do not exceed four stories
in height, the attic space shall be subdivided by draftstops
into areas not exceeding 3,000 square feet (279 m'2)
or above every two dwelling units, whichever is smaller.
4.Draftstopping
is not required in buildings equipped throughout with
an automatic sprinkler system in accordance with Section
903.3.1.2, provided that automatic sprinklers are
also installed in the combustible concealed spaces.
717.4.3
Other groups. Draftstopping shall be installed in attics
and concealed roof spaces, such that any horizontal area
does not exceed 3,000 square feet (279 m2).
Exception:
Draftstopping is not required in buildings equipped throughout
with an automatic sprinkler system in accordance with Section
903.3.1.1.
717.5
Combustible materials in concealed spaces in Type I or II
construction. Combustible materials shall not be permitted
in concealed spaces of buildings of Type I or II construction.
Exceptions:
1.Combustible
materials in accordance with Section 603.
2.Combustible
materials exposed within plenums complying with Section
602 of the International Mechanical Code.
3.Class
A interior finish materials classified in accordance with
Section 803.
4.Combustible
piping within partitions or shaft enclosures installed
in accordance with the provisions of this code.
5.Combustible
piping within concealed ceiling spaces installed in accordance
with the International Mechanical Code and the International
Plumbing Code.
6.Combustible
insulation and covering on pipe and tubing, installed in
concealed spaces other than plenums, complying with Section
719.7.
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