If you want to use an existing chimney for a stove or open fire, you should check whether your chimney needs to be lined or not.
Before the mid 1960s, chimneys in newly-built homes were not lined. Some were just simply brick chambers while, more commonly, others were rendered with a lime mortar (known as parging). Over time, this falls off due to age, exposing the brickwork underneath.
A smoke pressure test should be carried out to determine its condition. If smoke leaks into the house (or a neighbouring property if you live in a terrace or semi detatched property), it has failed the test and the chimney MUST either be repaired or lined if it is to be used.
If however it passes the pressure test, then you have two options; to line the chimney anyway or simply use what is there already.
My advice is always, even when a chimney passes the test, is to line the chimney. The primary reason is one of safety.
Without lining, there is a risk of deadly carbon monoxide fumes spreading into your house, or even your neighbours’ home. This could happen if, for instance, mortar in the chimney starts to decay, or a brick becomes cracked or dislodged.
Fumes from solid fuel fires are acidic and attack brickwork, slowly eating away at it. So while it may have passed the pressure test, there’s no guarantee it will stay airtight throughout the lifetime of your appliance.
The danger with carbon monoxide is that you cannot see, smell or taste it. A lined chimney is also easier to sweep, as the soot is easy to reach,so there is less risk of a chimney fire if it is swept regularly.
Yes, a chimney liner will cost you more, and there are a number of ways it can be lined. But for the added safety and peace of mind, I would – and I stress again that this is a personal view – always recommend getting a chimney lined.