Chimney connector construction.
Municipal Code of Chicago § 18-28-803.9
in effect18-28-803.9 Chimney connector construction.
Chimney connectors for low-heat appliances shall be made of sheet steel pipe that is resistant to corrosion and heat not less than that required for galvanized steel as specified in Table 18-28-803.9(1). Connectors for medium-heat appliances and high-heat appliances shall be of sheet steel not less than the thickness specified in Table 18-28-803.9(2).
Table 18-28-803.9(1)
Minimum Chimney Connector Thickness for Low- Heat Appliances
Diameter of Connector (inches) | Minimum Nominal Thickness (Galvanized) (inches)
5 and smaller | 0.022 (No. 26 Gauge)
Larger than 5 and up to 10 | 0.028 (No. 24 Gauge)
Larger than 10 and up to 16 | 0.034 (No. 22 Gauge)
Larger than 16 | 0.064 (No. 16 Gauge)
For SI: 1 inch = 25.4 mm, 1 square inch = 645.16 mm 2 .
Table 18-28-803.9(2)
Minimum Chimney Connector Thickness for Medium- and High-Heat Appliances
Area (square inches) | Equivalent Round Diameter (inches) | Minimum Nominal Thickness (inches)
0 – 154 | 0 – 14 | 0.060 (No. 16 Gauge)
155 – 201 | 15 – 16 | 0.075 (No. 14 Gauge)
202 – 254 | 17 – 18 | 0.105 (No. 12 Gauge)
Greater than 254 | Greater than 18 | 0.135 (No. 10 Gauge)
For SI: 1 inch = 25.4 mm, 1 square inch = 645.16 mm 2 .
Source: City of Chicago, Municipal Code of Chicago (American Legal Publishing, codelibrary.amlegal.com)URL: https://codelibrary.amlegal.com/codes/chicago/latest/chicago_il/0-0-0-2687864Fetched: 10/24/2026