International Building Code Section 2113


International Building Code 2113.1

Definition. A masonry chimney is a chimney constructed
of concrete or masonry, hereinafter referred to as
“masonry.” Masonry chimneys shall be constructed, anchored,
supported and reinforced as required in this chapter.

International Building Code 2113.10

Wall thickness. Masonry chimney walls shall be constructed
of concrete, solid masonry units or hollow masonry
units grouted solid with not less than 4 inches (102 mm) nominal
thickness.

Masonry veneer chimneys. Where masonry is
used as veneer for a framed chimney, through flashing and
weep holes shall be provided as required by Chapter 14.

International Building Code 2113.10.1

Masonry veneer chimneys. Where masonry is
used as veneer for a framed chimney, through flashing and
weep holes shall be provided as required by Chapter 14.

International Building Code 2113.11

Flue lining (material). Masonry chimneys shall be
lined. The lining material shall be appropriate for the type of
appliance connected, according to the terms of the appliance
listing and the manufacturer’s instructions.

Residential-type appliances (general). Flue
lining systems shall comply with one of the following:
1. Clay flue lining complying with the requirements of
ASTM C 315, or equivalent.
2. Listed chimney lining systems complying with UL
1777.
3. Factory-built chimneys or chimney units listed for
installation within masonry chimneys.
4. Other approved materials that will resist corrosion,
erosion, softening or cracking from flue gases and
condensate at temperatures up to 1,800F (982C).

Flue linings for specific appliances. Flue
linings other than those covered in Section 2113.11.1
intended for use with specific appliances shall comply
with Sections 2113.11.1.2 through 2113.11.1.4 and Sections
2113.11.2 and 2113.11.3.

Gas appliances. Flue lining systems for gas
appliances shall be in accordance with the International
Fuel Gas Code.

Pellet fuel-burning appliances. Flue lining
and vent systems for use in masonry chimneys with pellet
fuel-burning appliances shall be limited to flue lining
systems complying with Section 2113.11.1 and pellet
vents listed for installation within masonry chimneys
(see Section 2113.11.1.5 for marking).

Oil-fired appliances approved for use
with L-vent. Flue lining and vent systems for use in
masonry chimneys with oil-fired appliances approved
for use with Type L vent shall be limited to flue lining
systems complying with Section 2113.11.1 and listed
chimney liners complying with UL 641 (see Section
2113.11.1.5 for marking).

Notice of usage. When a flue is relined with
a material not complying with Section 2113.11.1, the
chimney shall be plainly and permanently identified by a
label attached to a wall, ceiling or other conspicuous
location adjacent to where the connector enters the chimney.
The label shall include the following message or
equivalent language: “This chimney is for use only with
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(type or category of appliance) that burns (type of fuel).
Do not connect other types of appliances.”

Concrete and masonry chimneys for
medium-heat appliances.

General. Concrete and masonry chimneys
for medium-heat appliances shall comply with Sections
2113.1 through 2113.5.

Construction. Chimneys for medium-heat
appliances shall be constructed of solid masonry units or
of concrete with walls a minimum of 8 inches (203 mm)
thick, or with stone masonry a minimum of 12 inches
(305 mm) thick.

Lining. Concrete and masonry chimneys
shall be lined with an approved medium-duty refractory
brick a minimum of 41/2 inches (114 mm) thick laid on
the 41/2-inch bed (114 mm) in an approved medium-duty
refractory mortar. The lining shall start 2 feet (610 mm)
or more below the lowest chimney connector entrance.
Chimneys terminating 25 feet (7620 mm) or less above a
chimney connector entrance shall be lined to the top.

Multiple passageway. Concrete and
masonry chimneys containing more than one passageway
shall have the liners separated by a minimum
4-inch-thick (102 mm) concrete or solid masonry wall.

Termination height. Concrete and
masonry chimneys for medium-heat appliances shall
extend a minimum of 10 feet (3048 mm) higher than any
portion of any building within 25 feet (7620 mm).

Clearance. A minimum clearance of 4
inches (102 mm) shall be provided between the exterior
surfaces of a concrete or masonry chimney for
medium-heat appliances and combustible material.

Concrete and masonry chimneys for
high-heat appliances.

General. Concrete and masonry chimneys
for high-heat appliances shall comply with Sections
2113.1 through 2113.5.

Construction. Chimneys for high-heat
appliances shall be constructed with double walls of
solid masonry units or of concrete, eachwall to be a minimum
of 8 inches (203 mm) thick with a minimum airspace
of 2 inches (51 mm) between the walls.

Lining. The inside of the interior wall shall
be lined with an approved high-duty refractory brick, a
minimum of 41/2 inches (114 mm) thick laid on the
41/2-inch bed (114 mm) in an approved high-duty refractory
mortar. The lining shall start at the base of the chimney
and extend continuously to the top.

Termination height. Concrete and
masonry chimneys for high-heat appliances shall extend
a minimum of 20 feet (6096 mm) higher than any portion
of any building within 50 feet (15 240 mm).

Clearance. Concrete and masonry chimneys
for high-heat appliances shall have approved clearance
from buildings and structures to prevent
overheating combustible materials, permit inspection
and maintenance operations on the chimney and prevent
danger of burns to persons.

International Building Code 2113.11.1

Residential-type appliances (general). Flue
lining systems shall comply with one of the following:
1. Clay flue lining complying with the requirements of
ASTM C 315, or equivalent.
2. Listed chimney lining systems complying with UL
1777.
3. Factory-built chimneys or chimney units listed for
installation within masonry chimneys.
4. Other approved materials that will resist corrosion,
erosion, softening or cracking from flue gases and
condensate at temperatures up to 1,800F (982C).

Flue linings for specific appliances. Flue
linings other than those covered in Section 2113.11.1
intended for use with specific appliances shall comply
with Sections 2113.11.1.2 through 2113.11.1.4 and Sections
2113.11.2 and 2113.11.3.

Gas appliances. Flue lining systems for gas
appliances shall be in accordance with the International
Fuel Gas Code.

Pellet fuel-burning appliances. Flue lining
and vent systems for use in masonry chimneys with pellet
fuel-burning appliances shall be limited to flue lining
systems complying with Section 2113.11.1 and pellet
vents listed for installation within masonry chimneys
(see Section 2113.11.1.5 for marking).

Oil-fired appliances approved for use
with L-vent. Flue lining and vent systems for use in
masonry chimneys with oil-fired appliances approved
for use with Type L vent shall be limited to flue lining
systems complying with Section 2113.11.1 and listed
chimney liners complying with UL 641 (see Section
2113.11.1.5 for marking).

Notice of usage. When a flue is relined with
a material not complying with Section 2113.11.1, the
chimney shall be plainly and permanently identified by a
label attached to a wall, ceiling or other conspicuous
location adjacent to where the connector enters the chimney.
The label shall include the following message or
equivalent language: “This chimney is for use only with
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(type or category of appliance) that burns (type of fuel).
Do not connect other types of appliances.”

International Building Code 2113.11.1.1

Flue linings for specific appliances. Flue
linings other than those covered in Section 2113.11.1
intended for use with specific appliances shall comply
with Sections 2113.11.1.2 through 2113.11.1.4 and Sections
2113.11.2 and 2113.11.3.

International Building Code 2113.11.1.2

Gas appliances. Flue lining systems for gas
appliances shall be in accordance with the International
Fuel Gas Code.

International Building Code 2113.11.1.3

Pellet fuel-burning appliances. Flue lining
and vent systems for use in masonry chimneys with pellet
fuel-burning appliances shall be limited to flue lining
systems complying with Section 2113.11.1 and pellet
vents listed for installation within masonry chimneys
(see Section 2113.11.1.5 for marking).

International Building Code 2113.11.1.4

Oil-fired appliances approved for use
with L-vent. Flue lining and vent systems for use in
masonry chimneys with oil-fired appliances approved
for use with Type L vent shall be limited to flue lining
systems complying with Section 2113.11.1 and listed
chimney liners complying with UL 641 (see Section
2113.11.1.5 for marking).

International Building Code 2113.11.1.5

Notice of usage. When a flue is relined with
a material not complying with Section 2113.11.1, the
chimney shall be plainly and permanently identified by a
label attached to a wall, ceiling or other conspicuous
location adjacent to where the connector enters the chimney.
The label shall include the following message or
equivalent language: “This chimney is for use only with
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(type or category of appliance) that burns (type of fuel).
Do not connect other types of appliances.”

International Building Code 2113.11.2

Concrete and masonry chimneys for
medium-heat appliances.

General. Concrete and masonry chimneys
for medium-heat appliances shall comply with Sections
2113.1 through 2113.5.

Construction. Chimneys for medium-heat
appliances shall be constructed of solid masonry units or
of concrete with walls a minimum of 8 inches (203 mm)
thick, or with stone masonry a minimum of 12 inches
(305 mm) thick.

Lining. Concrete and masonry chimneys
shall be lined with an approved medium-duty refractory
brick a minimum of 41/2 inches (114 mm) thick laid on
the 41/2-inch bed (114 mm) in an approved medium-duty
refractory mortar. The lining shall start 2 feet (610 mm)
or more below the lowest chimney connector entrance.
Chimneys terminating 25 feet (7620 mm) or less above a
chimney connector entrance shall be lined to the top.

Multiple passageway. Concrete and
masonry chimneys containing more than one passageway
shall have the liners separated by a minimum
4-inch-thick (102 mm) concrete or solid masonry wall.

Termination height. Concrete and
masonry chimneys for medium-heat appliances shall
extend a minimum of 10 feet (3048 mm) higher than any
portion of any building within 25 feet (7620 mm).

Clearance. A minimum clearance of 4
inches (102 mm) shall be provided between the exterior
surfaces of a concrete or masonry chimney for
medium-heat appliances and combustible material.

International Building Code 2113.11.2.1

General. Concrete and masonry chimneys
for medium-heat appliances shall comply with Sections
2113.1 through 2113.5.

International Building Code 2113.11.2.2

Construction. Chimneys for medium-heat
appliances shall be constructed of solid masonry units or
of concrete with walls a minimum of 8 inches (203 mm)
thick, or with stone masonry a minimum of 12 inches
(305 mm) thick.

International Building Code 2113.11.2.3

Lining. Concrete and masonry chimneys
shall be lined with an approved medium-duty refractory
brick a minimum of 41/2 inches (114 mm) thick laid on
the 41/2-inch bed (114 mm) in an approved medium-duty
refractory mortar. The lining shall start 2 feet (610 mm)
or more below the lowest chimney connector entrance.
Chimneys terminating 25 feet (7620 mm) or less above a
chimney connector entrance shall be lined to the top.

International Building Code 2113.11.2.4

Multiple passageway. Concrete and
masonry chimneys containing more than one passageway
shall have the liners separated by a minimum
4-inch-thick (102 mm) concrete or solid masonry wall.

International Building Code 2113.11.2.5

Termination height. Concrete and
masonry chimneys for medium-heat appliances shall
extend a minimum of 10 feet (3048 mm) higher than any
portion of any building within 25 feet (7620 mm).

International Building Code 2113.11.2.6

Clearance. A minimum clearance of 4
inches (102 mm) shall be provided between the exterior
surfaces of a concrete or masonry chimney for
medium-heat appliances and combustible material.

International Building Code 2113.11.3

Concrete and masonry chimneys for
high-heat appliances.

General. Concrete and masonry chimneys
for high-heat appliances shall comply with Sections
2113.1 through 2113.5.

Construction. Chimneys for high-heat
appliances shall be constructed with double walls of
solid masonry units or of concrete, eachwall to be a minimum
of 8 inches (203 mm) thick with a minimum airspace
of 2 inches (51 mm) between the walls.

Lining. The inside of the interior wall shall
be lined with an approved high-duty refractory brick, a
minimum of 41/2 inches (114 mm) thick laid on the
41/2-inch bed (114 mm) in an approved high-duty refractory
mortar. The lining shall start at the base of the chimney
and extend continuously to the top.

Termination height. Concrete and
masonry chimneys for high-heat appliances shall extend
a minimum of 20 feet (6096 mm) higher than any portion
of any building within 50 feet (15 240 mm).

Clearance. Concrete and masonry chimneys
for high-heat appliances shall have approved clearance
from buildings and structures to prevent
overheating combustible materials, permit inspection
and maintenance operations on the chimney and prevent
danger of burns to persons.

International Building Code 2113.11.3.1

General. Concrete and masonry chimneys
for high-heat appliances shall comply with Sections
2113.1 through 2113.5.

International Building Code 2113.11.3.2

Construction. Chimneys for high-heat
appliances shall be constructed with double walls of
solid masonry units or of concrete, eachwall to be a minimum
of 8 inches (203 mm) thick with a minimum airspace
of 2 inches (51 mm) between the walls.

International Building Code 2113.11.3.3

Lining. The inside of the interior wall shall
be lined with an approved high-duty refractory brick, a
minimum of 41/2 inches (114 mm) thick laid on the
41/2-inch bed (114 mm) in an approved high-duty refractory
mortar. The lining shall start at the base of the chimney
and extend continuously to the top.

International Building Code 2113.11.3.4

Termination height. Concrete and
masonry chimneys for high-heat appliances shall extend
a minimum of 20 feet (6096 mm) higher than any portion
of any building within 50 feet (15 240 mm).

International Building Code 2113.11.3.5

Clearance. Concrete and masonry chimneys
for high-heat appliances shall have approved clearance
from buildings and structures to prevent
overheating combustible materials, permit inspection
and maintenance operations on the chimney and prevent
danger of burns to persons.

International Building Code 2113.12

Clay flue lining (installation). Clay flue liners shall
be installed in accordance withASTMC 1283 and extend from
a point not less than 8 inches (203 mm) below the lowest inlet
or, in the case of fireplaces, from the top of the smoke chamber
to a point above the enclosing walls. The lining shall be carried
up vertically, with a maximum slope no greater than 30 degrees
(0.52 rad) from the vertical.
Clay flue liners shall be laid in medium-duty refractory mortar
conforming to ASTM C 199 with tight mortar joints left
smooth on the inside and installed to maintain an air space or
insulation not to exceed the thickness of the flue liner separating
the flue liners from the interior face of the chimney
masonrywalls. Flue lining shall be supported on all sides. Only
enough mortar shall be placed to make the joint and hold the
liners in position.

International Building Code 2113.13

Additional requirements.

Listed materials. Listed materials used as flue
linings shall be installed in accordance with the terms of
their listings and the manufacturer’s instructions.

Space around lining. The space surrounding a
chimney lining system or vent installed within a masonry
chimney shall not be used to vent any other appliance.
Exception: This shall not prevent the installation of a
separate flue lining in accordance with the manufacturer’s
instructions.

International Building Code 2113.13.1

Listed materials. Listed materials used as flue
linings shall be installed in accordance with the terms of
their listings and the manufacturer’s instructions.

International Building Code 2113.13.2

Space around lining. The space surrounding a
chimney lining system or vent installed within a masonry
chimney shall not be used to vent any other appliance.
Exception: This shall not prevent the installation of a
separate flue lining in accordance with the manufacturer’s
instructions.

International Building Code 2113.14

Multiple flues. When two or more flues are located
in the same chimney, masonry wythes shall be built between
adjacent flue linings. The masonry wythes shall be at least 4
inches (102 mm) thick and bonded into the walls of the chimney.
Exception: When venting only one appliance, two flues are
permitted to adjoin each other in the same chimney with
only the flue lining separation between them. The joints of
the adjacent flue linings shall be staggered at least 4 inches
(102 mm).

International Building Code 2113.15

Flue area (appliance). Chimney flues shall not be
smaller in area than the area of the connector from the appliance.
Chimney flues connected to more than one appliance
shall not be less than the area of the largest connector plus 50
percent of the areas of additional chimney connectors.
Exceptions:
1. Chimney flues serving oil-fired appliances sized in
accordance with NFPA 31.
2. Chimney flues serving gas-fired appliances sized in
accordance with the International Fuel Gas Code.

International Building Code 2113.16

Flue area (masonry fireplace). Flue sizing for chimneys
serving fireplaces shall be in accordance with Section
2113.16.1 or 2113.16.2.

Minimum area. Round chimney flues shall have
a minimum net cross-sectional area of at least 1/12 of the fireplace
opening. Square chimney flues shall have a minimum
net cross-sectional area of at least 1/10 of the fireplace open-
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ing. Rectangular chimney flues with an aspect ratio less than
2 to 1 shall have a minimum net cross-sectional area of at
least 1/10 of the fireplace opening. Rectangular chimney
flues with an aspect ratio of 2 to 1 or more shall have a minimum
net cross-sectional area of at least 1/8 of the fireplace
opening.

Determination of minimum area. The minimum
net cross-sectional area of the flue shall be determined
in accordance with Figure 2113.16. A flue size providing at
least the equivalent net cross-sectional area shall be used.
Cross-sectional areas of clay flue linings are as provided in
Tables 2113.16(1) and 2113.16(2) or as provided by the
manufacturer or as measured in the field. The height of the
chimney shall be measured from the firebox floor to the top
of the chimney flue.

International Building Code 2113.16.1

Minimum area. Round chimney flues shall have
a minimum net cross-sectional area of at least 1/12 of the fireplace
opening. Square chimney flues shall have a minimum
net cross-sectional area of at least 1/10 of the fireplace open-
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ing. Rectangular chimney flues with an aspect ratio less than
2 to 1 shall have a minimum net cross-sectional area of at
least 1/10 of the fireplace opening. Rectangular chimney
flues with an aspect ratio of 2 to 1 or more shall have a minimum
net cross-sectional area of at least 1/8 of the fireplace
opening.

International Building Code 2113.16.2

Determination of minimum area. The minimum
net cross-sectional area of the flue shall be determined
in accordance with Figure 2113.16. A flue size providing at
least the equivalent net cross-sectional area shall be used.
Cross-sectional areas of clay flue linings are as provided in
Tables 2113.16(1) and 2113.16(2) or as provided by the
manufacturer or as measured in the field. The height of the
chimney shall be measured from the firebox floor to the top
of the chimney flue.

International Building Code 2113.17

Inlet. Inlets to masonry chimneys shall enter from the
side. Inlets shall have a thimble of fireclay, rigid refractory
material or metal that will prevent the connector from pulling
out of the inlet or from extending beyond thewall of the liner.

International Building Code 2113.18

Masonry chimney cleanout openings. Cleanout
openings shall be provided within 6 inches (152 mm) of the
base of each flue within every masonry chimney. The upper
edge of the cleanout shall be located at least 6 inches (152 mm)
below the lowest chimney inlet opening. The height of the
opening shall be at least 6 inches (152 mm). The cleanout shall
be provided with a noncombustible cover.
Exception: Chimney flues serving masonry fireplaces,
where cleaning is possible through the fireplace opening.

International Building Code 2113.19

Chimney clearances. Any portion of a masonry
chimney located in the interior of the building or within the
exterior wall of the building shall have a minimum airspace
clearance to combustibles of 2 inches (51 mm). Chimneys
located entirely outside the exterior walls of the building,
including chimneys that pass through the soffit or cornice, shall
have a minimum airspace clearance of 1 inch (25 mm). The airspace
shall not be filled, except to provide fireblocking in
accordance with Section 2113.20.
Exceptions:
1. Masonry chimneys equipped with a chimney lining
system listed and labeled for use in chimneys in contact
with combustibles in accordance with UL 1777,
and installed in accordance with the manufacturer’s
instructions, are permitted to have combustible material
in contact with their exterior surfaces.
2. Where masonry chimneys are constructed as part of
masonry or concrete walls, combustible materials
shall not be in contact with the masonry or concrete
wall less than 12 inches (305 mm) from the inside surface
of the nearest flue lining.
3. Exposed combustible trim and the edges of sheathing
materials, such as wood siding, are permitted to abut
the masonry chimney sidewalls, in accordance with
Figure 2113.19, provided such combustible trim or
sheathing is a minimum of 12 inches (305 mm) from
the inside surface of the nearest flue lining. Combustible
material and trim shall not overlap the corners of
the chimney by more than 1 inch (25 mm).

International Building Code 2113.20

Chimney fireblocking. All spaces between chimneys
and floors and ceilings through which chimneys 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.
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For SI: 1 inch = 25.4 mm.
FIGURE 2113.19
ILLUSTRATION OF EXCEPTION THREE
CHIMNEY CLEARANCE PROVISION
416 2006 INTERNATIONAL BUILDING CODE

International Building Code 2113.2

Footings and foundations. Footings for masonry
chimneys shall be constructed of concrete or solid masonry at
least 12 inches (305 mm) thick and shall extend at least 6 inches
(152 mm) beyond the face of the foundation or support wall on
all sides. Footings shall be founded on natural undisturbed
earth or engineered fill belowfrost depth. In areas not subjected
to freezing, footings shall be at least 12 inches (305 mm) below
finished grade.

International Building Code 2113.3

Seismic reinforcing. Masonry or concrete chimneys
shall be constructed, anchored, supported and reinforced as
required in this chapter. In Seismic Design Category D,
masonry and concrete chimneys shall be reinforced and
anchored as detailed in Sections 2113.3.1, 2113.3.2 and
2113.4. In Seismic Design Category A, B or C, reinforcement
and seismic anchorage is not required. In Seismic Design Category
Eor F, masonry and concrete chimneys shall be reinforced
in accordance with the requirements of Sections 2101 through
2108.

Vertical reinforcing. For 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 hollow
unit masonry and grouted in accordance with Section
2103.12. Grout shall be prevented from bonding with the
flue liner so that the flue liner is free to move with thermal
expansion. For 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) o.c. 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.
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International Building Code 2113.3.1

Vertical reinforcing. For 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 hollow
unit masonry and grouted in accordance with Section
2103.12. Grout shall be prevented from bonding with the
flue liner so that the flue liner is free to move with thermal
expansion. For 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.

International Building Code 2113.3.2

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) o.c. 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.
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International Building Code 2113.4

Seismic anchorage. Masonry and concrete chimneys
and foundations 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 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 2113.4.1

Anchorage. Two 3/16-inch by 1-inch (4.8 mm by
25 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 2113.5

Corbeling. Masonry chimneys shall not be corbeled
more than half of the chimney’s wall thickness from a wall or
foundation, nor shall a chimney be corbeled from a wall or
foundation that is less than 12 inches (305 mm) in thickness
unless it projects equally on each side of thewall, except that on
the second story of a two-story dwelling, corbeling of chimneys
on the exterior of the enclosing walls is permitted to equal
the wall thickness. The projection of a single course shall not
exceed one-half the unit height or one-third of the unit bed
depth, whichever is less.

International Building Code 2113.6

Changes in dimension. The chimney wall or chimney
flue lining shall not change in size or shape within 6 inches
(152 mm) above or below where the chimney passes through
floor components, ceiling components or roof components.

International Building Code 2113.7

Offsets. Where a masonry chimney is constructed with
a fireclay flue liner surrounded by one wythe of masonry, the
maximum offset shall be such that the centerline of the flue
above the offset does not extend beyond the center of the chimney
wall below the offset. Where the chimney offset is supported
by masonry below the offset in an approved manner, the
maximum offset limitations shall not apply. Each individual
corbeled masonry course of the offset shall not exceed the projection
limitations specified in Section 2113.5.

International Building Code 2113.8

Additional load. Chimneys shall not support loads
other than their own weight unless they are designed and constructed
to support the additional load. Masonry chimneys are
permitted to be constructed as part of the masonrywalls or concrete
walls of the building.

International Building Code 2113.9

Termination. Chimneys shall extend at least 2 feet
(610 mm) higher than any portion of the building within 10 feet
(3048 mm), but shall not be less than 3 feet (914 mm) above the
highest point where the chimney passes through the roof.

Spark arrestors. Where a spark arrestor is
installed on a masonry chimney, the spark arrestor shall
meet all of the following requirements:
1. The net free area of the arrestor shall not be less than
four times the net free area of the outlet of the chimney
flue it serves.
2. The arrestor screen shall have heat and corrosion
resistance equivalent to 19-gage galvanized steel or
24-gage stainless steel.
3. Openings shall not permit the passage of spheres having
a diameter greater than 1/2 inch (13 mm) nor block
the passage of spheres having a diameter less than 3/8
inch (11 mm).
4. The spark arrestor shall be accessible for cleaning and
the screen or chimney cap shall be removable to allow
for cleaning of the chimney flue.

International Building Code 2113.9.1

Spark arrestors. Where a spark arrestor is
installed on a masonry chimney, the spark arrestor shall
meet all of the following requirements:
1. The net free area of the arrestor shall not be less than
four times the net free area of the outlet of the chimney
flue it serves.
2. The arrestor screen shall have heat and corrosion
resistance equivalent to 19-gage galvanized steel or
24-gage stainless steel.
3. Openings shall not permit the passage of spheres having
a diameter greater than 1/2 inch (13 mm) nor block
the passage of spheres having a diameter less than 3/8
inch (11 mm).
4. The spark arrestor shall be accessible for cleaning and
the screen or chimney cap shall be removable to allow
for cleaning of the chimney flue.