Types of chimneys

[edit] Introduction

In traditional construction, a chimney is a structure consisting of a wall or walls enclosing one or more flues. Scottish Building Standards define a chimney as: ‘…a structure enclosing one or more flues, but not a flue pipe, and including any openings for the accommodation of a combustion appliance, but does not include a chimney terminal.’ A chimney terminal is another term for a chimney pot, cowl or other structure that finishes off the chimney top.

[edit] Materials

Chimneys can be identified by the materials used in their construction. Common types include:

Brick. This common type of chimney found in residential construction can tolerate temperatures up to approximately 980C. However, since bricks are porous, they can deteriorate under certain climate conditions, and repointing can be necessary to prevent rainwater penetration.

Stone. Also porous, but it can be more expensive than brick. It is generally more difficult to build with stone when the shapes are irregular. Again, repointing can be necessary.

Concrete block. This is an easy to use and affordable material for chimney construction, and offers flexibility in terms of colour.

Metal. Metal is a good conductor of heat, although it can warp at high temperatures and must be lined for protection. Typically flues are made from metal.

Pre-fabricated materials. These factory built structures can be made to certain specifications (such as double-walled, air-cooled and so on).

Wood burning stovepipe chimneys. These vertical structures are attached to stoves and go through the ceiling and out through the roof. Due to the high temperatures of wood burning stoves, these chimneys must be able to withstand high heat. This may be referred to as a flue.

[edit] Chimney classes

[edit] Class 1

Traditional masonry chimneys found on older buildings (built before the 1960s) tend to be designated as Class 1. These chimneys are positioned on an internal or external wall and can contain more than one flue for more than one fire. However, fires cannot share the same flue. These chimneys tend to require liners, due to their age.

[edit] Class 2

Chimneys outfitted with pre-fabricated flues are categorised as Class 2. These chimneys can sometimes be identified by a metal chimney terminal. They are more commonly found in newer properties.

[edit] Related articles on Designing Buildings

• Approved Document J.
• BS EN 1443:2019.
• Chimney breast.
• Chimney definition.
• Flue definition.
• Flue insulation and air tightness requirements.
• Fireplace recess.
• Fluepipe.
• Hearth.
• Masonry chimney.
• Solar chimney.
• System chimney.