International Building Code Section 2111 – International Building Code 2006 Discussions

International Building Code 2111.1

Definition. A masonry fireplace is a fireplace constructed
of concrete or masonry. Masonry fireplaces shall be
constructed in accordance with this section.

International Building Code 2111.10

Hearth extension dimensions. Hearth extensions
shall extend at least 16 inches (406 mm) in front of, and at least
8 inches (203 mm) beyond, each side of the fireplace opening.
Where the fireplace opening is 6 square feet (0.557 m2) or
larger, the hearth extension shall extend at least 20 inches (508
mm) in front of, and at least 12 inches (305 mm) beyond, each
side of the fireplace opening.

International Building Code 2111.11

Fireplace clearance. Any portion of a masonry fireplace
located in the interior of a building or within the exterior
wall of a building shall have a clearance to combustibles of not
less than 2 inches (51 mm) from the front faces and sides of
masonry fireplaces and not less than 4 inches (102 mm) from
the back faces of masonry fireplaces. The airspace shall not be
filled, except to provide fireblocking in accordance with Section
2111.12.
Exceptions:
1. Masonry fireplaces listed and labeled for use in contact
with combustibles in accordance with UL 127
and installed in accordance with the manufacturer’s
installation instructions are permitted to have combustible
material in contact with their exterior surfaces.
2. When masonry fireplaces are constructed as part of
masonry or concrete walls, combustible materials
shall not be in contact with the masonry or concrete
walls less than 12 inches (306 mm) from the inside
surface of the nearest firebox lining.
3. Exposed combustible trim and the edges of sheathing
materials, such as wood siding, flooring and drywall,
are permitted to abut the masonry fireplace sidewalls
and hearth extension, in accordance with Figure
2111.11, provided such combustible trim or sheathing
is a minimum of 12 inches (306 mm) from the
inside surface of the nearest firebox lining.
4. Exposed combustible mantels or trim is permitted to
be placed directly on the masonry fireplace front surrounding
the fireplace opening, provided such combustible
materials shall not be placed within 6 inches
(153 mm) of a fireplace opening. Combustible material
directly above and within 12 inches (305 mm) of
the fireplace opening shall not project more than 1/8
inch (3.2 mm) for each 1-inch (25 mm) distance from
such opening. Combustible materials located along
the sides of the fireplace opening that project more
than 11/2 inches (38 mm) from the face of the fireplace
shall have an additional clearance equal to the projection.

International Building Code 2111.12

Fireplace fireblocking. All spaces between fireplaces
and floors and ceilings through which fireplaces pass
shall be fireblocked with noncombustible material securely
fastened in place. The fireblocking of spaces between wood
joists, beams or headers shall be to a depth of 1 inch (25 mm)
and shall only be placed on strips of metal or metal lath laid
across the spaces between combustible material and the chimney.

International Building Code 2111.13

Exterior air. Factory-built or masonry fireplaces covered
in this section shall be equipped with an exterior air supply
to ensure proper fuel combustion unless the room is mechanically
ventilated and controlled so that the indoor pressure is
neutral or positive.

Factory-built fireplaces. Exterior combustion
air ducts for factory-built fireplaces shall be listed components
of the fireplace, and installed according to the fireplace
manufacturer’s instructions.

Masonry fireplaces. Listed combustion air
ducts for masonry fireplaces shall be installed according to
the terms of their listing and manufacturer’s instructions.

Exterior air intake. The exterior air intake shall
be capable of providing all combustion air from the exterior
of the dwelling. The exterior air intake shall not be located
within the garage, attic, basement or crawl space of the
dwelling nor shall the air intake be located at an elevation
higher than the firebox. The exterior air intake shall be covered
with a corrosion-resistant screen of 1/4-inch (6.4 mm)
mesh.
410 2006 INTERNATIONAL BUILDING CODE
MASONRY
For SI: 1 inch = 25.4 mm
FIGURE 2111.11
ILLUSTRATION OF EXCEPTION TO
FIREPLACE CLEARANCE PROVISION
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Clearance. Unlisted combustion air ducts shall
be installed with a minimum 1-inch (25 mm) clearance to
combustibles for all parts of the duct within 5 feet (1524
mm) of the duct outlet.

Passageway. The combustion air passageway
shall be a minimum of 6 square inches (3870 mm2) and not
more than 55 square inches (0.035 m2), except that combustion
air systems for listed fireplaces or for fireplaces tested
for emissions shall be constructed according to the fireplace
manufacturer’s instructions.

Outlet. The exterior air outlet is permitted to be
located in the back or sides of the firebox chamber or within
24 inches (610 mm) of the firebox opening on or near the
floor. The outlet shall be closable and designed to prevent
burning material from dropping into concealed combustible
spaces.

International Building Code 2111.13.1

International Building Code 2111.13.2

Masonry fireplaces. Listed combustion air
ducts for masonry fireplaces shall be installed according to
the terms of their listing and manufacturer’s instructions.

International Building Code 2111.13.3

International Building Code 2111.13.4

Clearance. Unlisted combustion air ducts shall
be installed with a minimum 1-inch (25 mm) clearance to
combustibles for all parts of the duct within 5 feet (1524
mm) of the duct outlet.

International Building Code 2111.13.5

International Building Code 2111.13.6

International Building Code 2111.2

Footings and foundations. Footings for masonry fireplaces
and their chimneys shall be constructed of concrete or
solid masonry at least 12 inches (305 mm) thick and shall
extend at least 6 inches (153 mm) beyond the face of the fireplace
or foundation wall on all sides. Footings shall be founded
on natural undisturbed earth or engineered fill below frost
depth. In areas not subjected to freezing, footings shall be at
least 12 inches (305 mm) below finished grade.
408 2006 INTERNATIONAL BUILDING CODE
MASONRY
DESIGN WIND PRESSURE, psf
AREA OF PANEL, sq. ft.
For SI: 1 square foot = 0.0929 m2, 1 pound per square foot = 47.9 N/m2.
FIGURE 2110.3.1
GLASS MASONRY DESIGN WIND LOAD RESISTANCE
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Ash dump cleanout. Cleanout openings, located
within foundation walls below fireboxes, when provided,
shall be equipped with ferrous metal or masonry doors and
frames constructed to remain tightly closed, except when in
use. Cleanouts shall be accessible and located so that ash
removal will not create a hazard to combustible materials.

International Building Code 2111.2.1

International Building Code 2111.3

Seismic reinforcing. Masonry or concrete fireplaces
shall be constructed, anchored, supported and reinforced as
required in this chapter. In Seismic Design Category D,
masonry and concrete fireplaces shall be reinforced and
anchored as detailed in Sections 2111.3.1, 2111.3.2, 2111.4
and 2111.4.1 for chimneys serving fireplaces. In Seismic
Design Category A, B or C, reinforcement and seismic anchorage
is not required. In Seismic Design Category E or F,
masonry and concrete chimneys shall be reinforced in accordance
with the requirements of Sections 2101 through 2108.

Vertical reinforcing. For fireplaces with chimneys
up to 40 inches (1016 mm) wide, four No. 4 continuous
vertical bars, anchored in the foundation, shall be placed in
the concrete between wythes of solid masonry or within the
cells of hollowunit masonry and grouted in accordance with
Section 2103.12. For fireplaces with chimneys greater than
40 inches (1016 mm) wide, two additional No. 4 vertical
bars shall be provided for each additional 40 inches (1016
mm) in width or fraction thereof.

Horizontal reinforcing. Vertical reinforcement
shall be placed enclosed within 1/4-inch (6.4 mm) ties or
other reinforcing of equivalent net cross-sectional area,
spaced not to exceed 18 inches (457 mm) on center in concrete;
or placed in the bed joints of unit masonry at a minimum
of every 18 inches (457 mm) of vertical height. Two
such ties shall be provided at each bend in the vertical bars.

International Building Code 2111.3.1

International Building Code 2111.3.2

International Building Code 2111.4

Seismic anchorage. Masonry and concrete chimneys
in Seismic Design Category D shall be anchored at each floor,
ceiling or roof line more than 6 feet (1829 mm) above grade,
except where constructed completely within the exterior walls.
Anchorage shall conform to the following requirements.

Anchorage. Two 3/16-inch by 1-inch (4.8 mm by
25.4 mm) straps shall be embedded a minimum of 12 inches
(305 mm) into the chimney. Straps shall be hooked around
the outer bars and extend 6 inches (152 mm) beyond the
bend. Each strap shall be fastened to a minimum of four
floor joists with two 1/2-inch (12.7 mm) bolts.

International Building Code 2111.4.1

International Building Code 2111.5

Firebox walls. Masonry fireboxes shall be constructed
of solid masonry units, hollow masonry units grouted solid,
stone or concrete. When a lining of firebrick at least 2 inches
(51 mm) in thickness or other approved lining is provided, the
minimum thickness of back and sidewalls shall each be 8
inches (203 mm) of solid masonry, including the lining. The
width of joints between firebricks shall not be greater than 1/4
inch (6.4 mm). When no lining is provided, the total minimum
thickness of back and sidewalls shall be 10 inches (254 mm) of
solid masonry. Firebrick shall conform to ASTM C 27 or
ASTM C 1261 and shall be laid with medium-duty refractory
mortar conforming to ASTM C 199.

Steel fireplace units. Steel fireplace units are permitted
to be installed with solid masonry to form a masonry
fireplace provided they are installed according to either the
requirements of their listing or the requirements of this section.
Steel fireplace units incorporating a steel firebox lining
shall be constructed with steel not less than 1/4 inch (6.4 mm)
in thickness, and an air-circulating chamber which is ducted
to the interior of the building. The firebox lining shall be
encased with solid masonry to provide a total thickness at
the back and sides of not less than 8 inches (203 mm), of
which not less than 4 inches (102 mm) shall be of solid
masonry or concrete. Circulating air ducts employed with
steel fireplace units shall be constructed of metal or
masonry.

International Building Code 2111.5.1

International Building Code 2111.6

Firebox dimensions. The firebox of a concrete or
masonry fireplace shall have a minimum depth of 20 inches
(508 mm). The throat shall not be less than 8 inches (203 mm)
above the fireplace opening. The throat opening shall not be
less than 4 inches (102 mm) in depth. The cross-sectional area
of the passageway above the firebox, including the throat,
damper and smoke chamber, shall not be less than the
cross-sectional area of the flue.
Exception: Rumford fireplaces shall be permitted provided
that the depth of the fireplace is at least 12 inches (305 mm)
and at least one-third of the width of the fireplace opening,
and the throat is at least 12 inches (305 mm) above the lintel,
and at least 1/20 the cross-sectional area of the fireplace opening.

International Building Code 2111.7

Lintel and throat. Masonry over a fireplace opening
shall be supported by a lintel of noncombustible material. The
minimum required bearing length on each end of the fireplace
opening shall be 4 inches (102 mm). The fireplace throat or
damper shall be located a minimum of 8 inches (203 mm)
above the top of the fireplace opening.

Damper. Masonry fireplaces shall be equipped
with a ferrous metal damper located at least 8 inches (203
mm) above the top of the fireplace opening. Dampers shall
be installed in the fireplace or at the top of the flue venting
the fireplace, and shall be operable from the room containing
the fireplace. Damper controls shall be permitted to be
located in the fireplace.

International Building Code 2111.7.1

International Building Code 2111.8

Smoke chamber walls. Smoke chamber walls shall be
constructed of solid masonry units, hollow masonry units
grouted solid, stone or concrete. Corbeling of masonry units
shall not leave unit cores exposed to the inside of the smoke
chamber. The inside surface of corbeled masonry shall be
parged smooth. Where no lining is provided, the total minimum
thickness of front, back and sidewalls shall be 8 inches
(203 mm) of solid masonry. When a lining of firebrick at least 2
inches (51 mm) thick, or a lining of vitrified clay at least 5/8 inch
(15.9 mm) thick, is provided, the total minimum thickness of
front, back and sidewalls shall be 6 inches (152 mm) of solid
masonry, including the lining. Firebrick shall conform to
ASTM C 27 or ASTM C 1261 and shall be laid with refractory
mortar conforming to ASTM C 199.

Smoke chamber dimensions. The inside height
of the smoke chamber from the fireplace throat to the beginning
of the flue shall not be greater than the inside width of
the fireplace opening. The inside surface of the smoke
chamber shall not be inclined more than 45 degrees (0.76
2006 INTERNATIONAL BUILDING CODE 409
MASONRY
rad) from vertical when prefabricated smoke chamber linings
are used or when the smoke chamberwalls are rolled or
sloped rather than corbeled. When the inside surface of the
smoke chamber is formed by corbeled masonry, the walls
shall not be corbeled more than 30 degrees (0.52 rad) from
vertical.

International Building Code 2111.8.1

International Building Code 2111.9

Hearth and hearth extension. Masonry fireplace
hearths and hearth extensions shall be constructed of concrete
or masonry, supported by noncombustible materials, and reinforced
to carry their own weight and all imposed loads. No
combustible material shall remain against the underside of
hearths or hearth extensions after construction.

Hearth thickness. The minimum thickness of
fireplace hearths shall be 4 inches (102 mm).

Hearth extension thickness. The minimum
thickness of hearth extensions shall be 2 inches (51 mm).
Exception: When the bottom of the firebox opening is
raised at least 8 inches (203 mm) above the top of the
hearth extension, a hearth extension of not less than
3/8-inch-thick (9.5 mm) brick, concrete, stone, tile or
other approved noncombustible material is permitted.

International Building Code 2111.9.1