Older houses built before 1960 would commonly have a class 1 chimney with a 7″ (180mm) diameter or larger flue. Usualy consisting of a brick built “stack” situated on a external or a internal wall. A class 1 chimney can contain multiple flues for gas or solid fuel fires, with each fire flue working individually and not sharing.
With a class 1 chimney you can install all types of fires and fireplaces including all types of gas fires providing the unit will fit in to your chimney breast, solid fuel fires inset and freestanding wood and multi-fuel stoves will normally fit in to a chimney. ( Excluding some European wood burning stoves that may require a larger flue size).
A class 2 flue 5″ (127mm) diameter can be found in new homes and older homes built from 1960 onwards where the existing chimney as been lined with a propietary steel flue or a new house with a steel flue built in. There are many gas fires available for a class 2 flue from many companies including Legend, Paragon, Kinder, and Flavell, all subject to the depth of the chimney fireplace.
Class 2 Precast
A precast flue will be often found in new homes and houses built later than 1960, consisting of a precast concrete chimney system. Only specific gas fires can be used in a pre cast flue (solid fuel fires can not be installed). Many companies now supply eye catching slimline gas fires to suite the shallow depth in this type of flue.
Many modern new homes and extensions are built with no chimney. There are many options now available in the marketplace including electric fires, flueless fires, power flue fires (external wall required) . Balanced flue glass fronted gas fires are now very popular with many leading companies including Dru who have developed high end fires to fit in many situations including bedrooms, Kitchens, loft conversions and many other places. You can now install fires up to 1.5 meters wide or tall to go in corners, panoramic viewing windows and tunnel fires for views in to a through room. Balanced flue systems draw air from the outside for combustion and and then expel gases to the outside as well.
A fireplace can now be created in almost any living room with a specially-made replica chimneybreast. These breast are made of steel and heat resistent board and modelled to fit each fire installation. If there is no outside wall the flue can be installed vertically through the roof if structurally appropriate. With the new Dru powervent system you can extend even further, this opens up the option of having gas fire in the most accessible locations.