Chimneys and Fireplace Sizing

Chimneys and fireplace sizing for fireplaces and stoves burning wood or coal as fuel

Chimneys can be separated in two main categories:

  • metal
  • masonry

chimney sizing

Prefab or Metal Chimneys

Prefab or metal chimneys, class A and double or triple walls are usually found in three diameters. Each diameter has a specific useable area, which is also called it's cross section.

The capacity of a chimney to remove smoke and/or energy (BTU's) from an appliance is directly related to the cross section area.

Chimney Size Square Inches Common Venting Uses
6 Inch Inside Diameter 28.3 Stoves, Central Heaters
7 Inch Inside Diameter 38.5 Stoves, Central Heaters
8 Inch Inside Diameter 50.3 Stoves, Small Fireplaces, Central Heaters
10 Inch Inside Diameter 78.6 Stoves, Fireplaces, Central Heaters
12 Inch Inside Diameter 113 Fireplaces, Central Heaters

Masonry Flues

Flue Size
(Outside Diameter)
Square Inches Common Venting Uses
7 1/2 X 7 1/2 31 Stoves, Central Heaters
8 1/2 x 8 1/2 41 Stoves, Central Heaters
8 1/2 X 13 70 Stoves, Fireplaces, Central Heaters
13 X 13 99 Fireplaces
13 X 18 156 Fireplaces

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