It serves as important function both when your fire is on or off!

If you’ve had an open fire swept by a chimney sweep, then you may have heard them refer to ‘backfill’.

The reason is that a large number of open fires – be it gas or coal – either do not have backfill or, if they do, it’s starting to perish.

What Is Backfill?

Put simply, backfill is a way of ‘filling’ in the gap betwen the ‘back’ of your open fire and the wall behind the chimney breast. Hence the term ‘backfill’.

What Is Backill Made Of?

Backfill can be made up of any non-combustible material which is capable of filling the void between the back of your open fire and the wall behind your chimney breast.

Traditionally, it can simply be building rubble, or vermiculite with a layer of sand and cement on top.

What’s The Point Of Backfill?

Backfill provides a number of important functions. These include

#1 – Stopping any soot and debris falling down the back of the fire and getting trapped. Soot at the back of a fireplace can easily catch fire.

#2 – Stopping any wildlife (such as birds) getting stuck behind and the fireplace without any means of getting them out

#3 – Can help retain and therefore reflect heat back into the room, as well as dispersing heat from cast iron firebacks so they don’t burn through as quickly

#4 – Helping assist the ‘draw’ of the chimney by reducing the ‘void’ at the back of the fire and…

#5 – Simultaneously, the ’benching’ at the top of the backfill help create a smooth passage for smoke to pass through the ’throat’ of the fire and into the chimney

How Do I know If My Open Fire Is Backfilled?

Generally, you should be able to see it at the back of the fire. However, if in doubt, ask your sweep to check when they’re next cleaning the flue.

What Will Happen If My Open Fire Isn’t Backfilled?

Many open fires are either not backfilled at all, or inadequately backfilled. These all run the risk of:

Becoming a void for trapped wildlife, including birds and mice (yes, we’ve even seen mouse traps at the back of open fires!)

A chimney fire and/or smoking into the room because of the build up of irretrievable soot at the back of the fireplace

The fire not working in the way in was intended

Shorter lifespan of the fireback if it is made of cast iron

How Can I Get My Open Fire Backfilled?

To ensure backfilling is done to the correct standards and guidance, you’re always advised to use either a professional, qualified chimney sweep or a registered solid fuel installer.

If you are minded to do it yourself, please ensure you follow the relevant standards for your local area/country.