Here is a conclusive run down all about flues to remove much “conflusion”:

Class 1

A fire (Gas, Oil or solid fuel) that require a “CLASS 1” flue.

By simple definition this is a flue that would be suitable to burn coal in. The most obvious and familiar Class 1 flues are the brick built chimneys that we see around on most older houses. Class 1 need not necessarily be brick however. Today Class 1 flue systems are built in steel, volcanic pumice, as well as the traditional building methods. Some gas fires require Class 1 systems to support them, usually where a large open fire is envisaged, this because the larger the fire the more air will be transported up the flue and Class 1 flues are normally at least 7” in diameter.

Class 2

This type of flue is less robust than a Class 1 system and is almost exclusively the province of the gas market. Class 2 flues, again may be built from a variety of materials, but often are constructed in aluminium. Adding a liner to a Class 1 flue reducing the diameter to 5”, normally, will turn it into a Class 2. The smaller diameter and lesser materials, ensure that Class 2 flues are used for smaller “Reduced draught” open gas fires, glass fronted gas fires and some gas stoves.

Class 2 Precast

A special type of Class 2 flue, beloved of builders of new properties! The Class 2 Precast is a block system that can be easily incorporated into the wall of a new building. It is usually evidenced externally by a raised ridge tile as a termination. Again, this type of flue is limited in the amount of fumes it can transport, so are limited in the range of fires and stoves they can support.


Relatively new to the market, Flueless gas fires are based on Catalytic Converter technology. They are often described as 100% efficient. What is meant by this is that ALL the products of the burning of the gas are released in to the room. Please note, it is NOT all heat! Because of this there are some restrictions on the use of Flueless appliances. The output of the appliance must be related to room size. Usually in the range of 30—40 cubic metres. The room MUST be ventilated. The size of the vent dictated by the manufacturer and Gas Safe.

Balanced Flue

Balanced flue appliances are unique in being the only appliances that do NOT make use of the room air to feed the fire. A Balanced Flue pipe is double skinned with the exhaust from the fire travelling through the core and fresh air being drawn from outside the building through the outer wall of the pipe. Because of this Balanced flue fires have no requirement for room ventilation. They are often described as “Room Sealed”. Because of this unique flue construction, ALL balanced flue fires are glass fronted.

Power Flue

To answer the call for the large open gas fire where no option exists with regard to constructing a Class 1 flue a Power Flue may be the best option. In effect the fumes from the fire are passed through a pipe leading outside and forced to travel with the addition of an external fan unit. Power flues can solve a lot of construction problems but do bring their own handicaps. The fire will be electrically dependent (i.e If the power supply fails to the fan unit, the gas supply will be shut off.) These are gas fires that will NOT operate in a power cut! There can also be some noise from the fan unit. How much, can depend on the proximity of the fan to the fire, type of fire, fluepipe etc.

NB This is a VERY brief, identifier. Before choosing your fire, be sure on the type of flueing arrangements that you have or are prepared to have installed in your home. There are also many qualifications with regard to the height of flues, where they may terminate outside your home, external appearance, etc. Most of this information is best gleaned from current building regulations or your local planning officer. If we can help in this regard, please ask! Just call us on 0800 587 9087.

We offer a full range of Flue fitting services:

  1. Class 2 Flue 5" Loft through roof with Cowl & Lead flashing.
  2. Class 1 Class 2 5" - 8" from lounge to roof with flue box, lead flashing & Cowl.
  3. Ridge Vent for Class 2 if all pipe work is in good working order.
  4. Flue Extension: 5" BVent or 5" IL If your flue is too short & needs to be higher on roof.
  5. Flue Inner Flexi 5" & Cowl & Plate.
  6. Multi Fuel Stoves fitted with liners
  7. Gas Stoves fitted with liners
  8. Fire Places fitted


Fitting Prices

All prices quoted are for fitting and materials.

1) Class 2 Loft
2) Class 1 Class 2 Lounge to Roof
£POA - Measuring req'd
3) Ridge Vent
4) Flue Extension
5) Flexi
6) Multi Fuel Stoves fitted with liners
Measuring Required
5) Gas Stoves fitted with liners
Measuring Required
4) Fire Places fitted
Measuring Required