Last edited 19 Mar 2021

Chimney breast

A chimney is typically a stone, block or brick structure consisting of a wall or walls enclosing one or more flues. A chimney breast is the part of the chimney structure that projects into or out of the building.

A flue is a passage that conveys the products of combustion from a combustion appliance to the outside air.

The front of the chimney breast is carried over and above a fireplace on a structure referred to as a chimney bar. A fireplace is a very simple combustion chamber, with or without front door, in which fuels are oxidised to obtain thermal energy, which is transferred into a space mainly by radiation.

In many older buildings fireplaces may have been removed, but the chimney breast may have been retained as they can form a significant part of the structure supporting the building. Where fireplaces have been removed, it is best practice to introduce ventilation at the bottom of the flue and to leave it open at the top (perhaps with a cowl to prevent rainwater penetration) to prevent the accumulation of moisture and potential deterioration of the structure. Unused flues may be filled with inert insulating material such as vermiculite that allows some continued movement of air for ventilation.

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