UpCodes logo
Go To Full Code Chapter
Flue sizing for chimneys serving fireplaces shall be in accordance with Section 2113.16.1 or 2113.16.2.
Note: 1 inch = 25.4 mm, 1 square inch = 645 mm2.
FIGURE 2113.16
FLUE SIZES FOR MASONRY CHIMNEYS
 
TABLE 2113.16(1)
NET CROSS-SECTIONAL AREA OF ROUND FLUE SIZESa
FLUE SIZE, INSIDE DIAMETER (inches) CROSS-SECTIONAL AREA (square inches)
6 28
7 38
8 50
10 78
103/4 90
12 113
15 176
18 254
For SI: 1 inch = 25.4 mm, 1 square inch = 645.16 mm2.
  1. Flue sizes are based on ASTM C315.
NET CROSS-SECTIONAL AREA OF SQUARE AND RECTANGULAR FLUE SIZES
FLUE SIZE, OUTSIDE NOMINAL DIMENSIONS (inches) CROSS-SECTIONAL AREA (square inches)
4.5 × 8.5 23
4.5 × 13 34
8 × 8 42
8.5 × 8.5 49
8 × 12 67
8.5 × 13 76
12 × 12 102
8.5 × 18 101
13 ×13 127
12 × 16 131
13 × 18 173
16 × 16 181
16 × 20 222
18 × 18 233
20 × 20 298
20 × 24 335
24 × 24 431
For SI: 1 inch = 25.4 mm, 1 square inch = 645.16 mm2.
2113.16.1 Minimum Area
Round chimney flues shall have a minimum net cross-sectional area of not less than 1/12 of the fireplace opening. Square chimney flues shall have a minimum net cross-sectional area of not less than 1/10 of the fireplace opening. Rectangular chimney flues with an aspect ratio less than 2 to 1 shall have a minimum net cross-sectional area of not less than 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 not less than 1/8 of the fireplace opening.
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 not less than 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.

Related Code Sections

2113.16 Masonry, Flue Area (Masonry Fireplace)
= 645 mm2. FIGURE 2113.16 FLUE SIZES FOR MASONRY CHIMNEYS TABLE 2113.16(1) NET CROSS-SECTIONAL AREA OF ROUND FLUE SIZESa FLUE SIZE, INSIDE ...
2113.16 Masonry, Flue Area (Masonry Fireplace)
= 645 mm2. FIGURE 2113.16 FLUE SIZES FOR MASONRY CHIMNEYS   TABLE 2113.16(1) NET CROSS-SECTIONAL AREA OF ROUND FLUE SIZESa ...
2111.7 Masonry, Firebox Dimensions
the firebox, including the throat, damper and smoke chamber, shall be not less than the cross-sectional area of the flue. Exception: Rumford fireplaces ...
2111.7 Masonry, Firebox Dimensions
the firebox, including the throat, damper and smoke chamber, shall be not less than the cross-sectional area of the flue. Exception: Rumford fireplaces ...
Section 2111 Masonry, Masonry Fireplaces
chamber, shall be not less than the cross-sectional area of the flue. Exception: Rumford fireplaces shall be permitted provided that the depth ...