The anatomy of a chimney

by | Feb 20, 2023

The anayomy of a chimney

Do you know the different parts of a chimney stack and their functions?

It is helpful to have this knowledge as you examine your chimney for repairs or choose a company to do the repair. Learning this information will help you make a better decision when dealing with a chimney and help you understand the recommendations the repair company makes.

A chimney stack is a term that means the outer parts of a chimney over the roof line. Here is a description of the chimney stack from the uppermost position to the lowest part and the function of each component.

Chimney Cowls

This part of a chimney is the cover put over a chimney pot and has ventilation openings. In chimneys that are in good working condition, the function of a cowl is to block smoke emanating from the flue from flowing back inside the building. When you stop using your chimney, ensure that you install a C-cap to prevent rainwater from entering your home. Additionally, they also prevent birds, squirrels, pests and debris from entering the chimney.

Chimney Cowls | Chimney C-caps

Chimney Pots

These ventilate flues and make extra breezes which help fires burn better by providing them with oxygen. In the UK, chimney pots are usually made using clay and, if installed firmly, will serve you for decades.


This word refers to the mortar layer on the top course of stonework. It is made using a strong mortar mixture and has two uses. The first use is to ensure rainwater is directed away from the stack before it can drench the brickwork underneath. The second use is to make sure the chimney pots stay in place firmly. This part of the chimney can get cracks and needs immediate repair if you notice any damage.

Chimney Stack

The main structure of the chimney is the stack. This section is made using brick and mortar. Mortar is weaker and usually gets cracks. When the mortar starts to develop cracks, you should have professionals perform repointing as soon as possible to avoid water penetrating and destroying the bricks, which could affect the structural integrity of the chimney, necessitating a chimney reconstruction.


Chimney flashing is a band of metal that runs around the base of the chimney stack, creating a water tight seal between the chimney stack and the roof. The standard material used to make flashing is sheet lead, but other times mortar or tin is used. They are highly beneficial in preventing chimney leaks. Flashing should be installed on every side of a chimney stack to prevent water from entering and requires frequent inspection for faults.

Knowing the parts of a chimney and their functions is vital before hiring an expert to repair it for you. We hope this short explanation will help you learn more about your chimney. If you require professional assistance with your chimney please get contact us.