ICC Subscriptions
 
SECTION 1003 MASONRY FIREPLACES

1003.1 Fireplace support.


Fireplace foundations and supporting walls shall be anchored, supported and reinforced as required in Sections 1003.1 through 1003.12, Table 1003.1, Figure 1003.1, and the applicable provisions of Chapters 3 and 4. Foundations for masonry fireplaces and their chimneys shall be constructed of concrete or solid masonry at least 12 inches (305 mm) thick and extend at least 6 inches (153 mm) beyond the face of the fireplace or supporting 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.

TABLE 1003.1 REQUIREMENTS FOR MASONRY FIREPLACES AND CHIMNEYS


ITEM
LETTER1
REQUIREMENTS
Hearth slab thickness
A
4"
Hearth extension
(each side of opening)
B
8" fireplace opening < 6 sq. ft.
12" fireplace opening > 6 sq. ft
Hearth extension
(front of opening)
C
16" fireplace opening < 6 sq ft.
20"  fireplace opening > 6 sq. ft.
Hearth slab reinforcing
D
Reinforced to carry its own weight and all imposed loads.
Thickness of wall of firebox
E
10" solid brick or 8" where a firebrick lining is used. Joints in firebrick ¼" max.
Distance from top of opening to throat
F
8"
Smoke chamber edge of shelf
Rear wall-thickness
Front and sidewall-thickness
G

6"
8"
Chimney 
Vertical Reinforcing2
H
Four No. 4 full-length bars for chimney up to 40" wide. Add two No. 4 bars for each additional 40" or fraction of width or each additional flue.
Horizontal reinforcing2
J
¼ " ties at 18" and two ties at each bend in vertical steel.
Bond beams
K
No specified requirements.
Fireplace lintel
L
Noncombustible material.
Walls with flue lining
M
Brick with grout around lining or ½" airspace 4" min. from flue lining to outside face of chimney.
Walls with unlined flue
N
8"  solid masonry.
Distances between adjacent flues
-
See Section 1001.9
Effective flue area (based on area of fireplace opening)
P
See Section 1001.11
Clearances
Wood frame
 Combustible material
Above roof

R

See  Sections 1001.14 and 1003.9
See Section 1003.11
2' at 10'

Anchorage2
Strap
Number
Embedment into chimney 

Fasten to
Bolts
S

3/16" x 1"
2
12" hooked around outer bar w/6" ext.
4 joists
Two ½" diameter.
Footing
Thickness
Width
T

12" min.
6" each side of fireplace wall.

For SI:   1 inch = 25.4 mm, 1 foot = 304.8 mm.

1
   The letters refer to Figure 1003.1.

2
   Not required in Seismic Zone 0, 1 or 2.


object has 0 width or height




For SI:   1 inch = 25.4 mm, 1 foot = 304.8 mm.

FIGURE 1003.1 FIREPLACE AND CHIMNEY DETAILS


1003.2 Seismic reinforcing.


Masonry or concrete chimney in Seismic Zones 3 and 4 extending more than 7 feet (2134 mm) above the last contact with the structure shall be reinforced. Reinforcing shall conform to the requirements set forth in Table 1003.1. When the width of the chimney exceeds 40 inches (1016 mm), two additional No. 4 vertical bars shall be provided for each additional flue incorporated in the chimney or for each additional 40 inches (1016 mm) in width or fraction thereof.

1003.3 Seismic anchorage.


In Seismic Zones 3 and 4, masonry and concrete chimneys shall be anchored at each floor-ceiling or roof line more than 6 feet (1829 mm) above grade, except when constructed completely within the exterior walls. Anchorage shall conform to the requirements set forth in Table 1003.1.

1003.4 Fireplace walls.


Masonry fireplaces shall be constructed of solid masonry units, stone or reinforced concrete in accordance with Figure 1003.1. When a lining of firebrick at least 2 inches (51 mm) in thickness is provided, the total thickness of back and sides, including the lining, shall not be less than 8 inches (203 mm). When no lining is provided, the thickness of back and sides shall not be less than 10 inches (254 mm).

1003.5 Steel fireplace units.


Steel fireplace units incorporating a firebox liner of not less than ¼ inch (6.4 mm) in thickness and an air chamber may be installed with 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. Warm-air ducts employed with steel fireplace units of the circulating air type shall be constructed of metal or masonry.

1003.6 Lintel.


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).

1003.7 Hearth extension material.


Hearth extensions shall be of masonry or concrete at least 2 inches (51 mm) thick and supported by noncombustible materials and reinforced to carry its own weight and all imposed loads. The hearth extension shall be readily distinguishable from the surrounding floor. Combustible forms and centers used during the construction of the hearth extension shall be removed after the construction is complete.

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 may be used.

1003.8 Hearth extension.


The hearth and the hearth extension shall extend a minimum of 36 inches (914 mm) from the back of the firebox to the end of the hearth extension. 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.

1003.9 Fireplace clearance.


Wood or combustible framing shall not be placed within 2 inches (51 mm) of the outside face of a masonry fireplace and not less than 6 inches (153 mm) from the inside surface of the nearest flue lining. Wood framing and other combustible material shall not be placed within 2 inches (51 mm) of the back surface of a masonry fireplace.

1003.10 Fireplace firestopping.


See Section 602.7.

1003.11 Combustible materials.


Woodwork or other combustible materials shall not be placed within 6 inches (153 mm) of a fireplace opening. Combustible material 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.

1003.12 Ash dump cleanout.


Cleanout openings, when provided, shall be equipped with ferrous metal 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.