A common class 1 chimney stack

The origin of the humble chimney, designed to carry smoke out of the dwelling, remains unclear. There was initially little understanding of the physics of chimney draught, so many early domestic fires were simple open hearths where smoke billowed around inside the room before escaping through a hole in the roof.

Incredibly, in England it wasn’t until the 16th Century that chimneys were widely adopted by the upper classes during Tudor England. Common folk lacking the funds to construct chimneys continued to be plagued with smoke filled rooms. Over the following centuries, as more chimneys were built the standards of construction improved as well.

Overcrowding in cities highlighted the danger of poorly contained fires. After the Great Fire of London in 1666 that destroyed over 80% of the city, regulations concerned with fire safety became more prominent and surveyors were provided to enforce them. These regulations specified that houses were to be built of brick or stone and that streets should be wide enough to act as fire breaks. By 1719, it was required that all chimneys be built or rebuilt in brick only.

Until the 1960’s all chimneys built were what is known as ‘Class 1’ chimneys. These are sufficient in diameter and construction for solid fuel fires. From the 1960’s onward, due to the increasing popularity of gas fires and central heating, many homes were built with smaller flues, only suitable for gas fires.

The following summary can help you work out which type of chimney you have.

  • A Class 1 chimney is common in houses built up until the 1960s. They consist of a brick-built stack, situated on either an internal or external wall and may contain multiple flues for multiple fires. Due to its construction and diameter of at least 7", this type of chimney can be used with all types of solid fuel and gas appliances. 

Class 2 chimneys are often found in houses built in or after the 1960s and they come in two types:

An interlocking metal pipe running through the house, ending with a metal flue terminal on the roof.

An interlocking metal pipe running through the house, ending with a metal flue terminal on the roof.

A hollow rectangular concrete or clay blocks that travel through the wall cavity to a ridge vent

A hollow rectangular concrete or clay blocks that travel through the wall cavity to a ridge vent.

These are called ‘pre-cast flues’. They are suitable for gas fires but cannot be used for solid fuel fires. 

Chimneys come in all shapes and sizes and the specification of yours will not always be readily apparent. At Ambience: Fires & Stoves we will always carry out a home visit to assess your chimney suitability for your chosen fire. We can even install flue systems to allow you to enjoy the benefits of a solid fuel stove or gas fire even if you do not have a chimney!