What is a Class 1 or a Class 2 fireplace?

Having a beautiful cast iron fireplace as the focal point in your room can enhance the interior décor of the room considerably. And when you have a living flame gas fire, the effect can be truly stunning.

When you buy your cast iron fireplace, you will have a number of options to choose from regarding the fire insert. You can choose from an electric option, a real fire option, a Class 1 gas fire and a Class 2 fire. You can probably tell the difference between an electric fire and a real (open hearth) fire, but do you know the difference between Class 1 and Class 2 gas fires?

Class 1 and Class 2 fireplaces

The choice of a Class 1 or a Class 2 fireplace is determined by the type of chimney and flue you have in your house. And, in fact, this can play a significant part of your cast iron fireplace choice too.

You chimney or flue type can be determined by a survey from a qualified Gas Safe registered engineer.

Class 1 flue fires

If you have a standard chimney which is easily recognisable on your roof, the likelihood is you will have a flue diameter of 7” or greater. If the chimney is very old, it may not be airtight, so a liner should be fitted. But this type of chimney should be able to support a Class 1 fire.

Class 2 fire flues

If you have a pre-fabricated flue or a pre-cast flue, the chances are, you will need a Class 2 fire. A pre-fabricated flue is usually distinguishable by the metal gas terminal on your roof. This will usually have a flue diameter of about 5”. Pre-cast flues usually use block work in the cavity in a similar method to a standard chimney. However they are very shallow and don’t offer a great deal of extraction, you might notice a ridge vent or gas terminal on your roof in this instance.

In summary, it really does depend on the size of flue you have whether you can have a Class 1 or a Class 2 fire. For flues of 7” or larger, Class 1 is appropriate. For flues less than 7” that are around 5” in diameter Class 2 is the right choice.


Leave a Reply