Mutual chimneys will often carry flues from the neighbouring tenement, as well as from your own, and costs will be shared between both tenements.
Mutual and gable chimneys are built at the top of cross or gable walls. The mutual chimney is shared between two neighbouring buildings. However, even in older stone tenements, the wall below a mutual chimney is generally made of brick (gable walls in older tenements are commonly built in a rubble or rough finished stone).
As the flues feed up through the walls, the stonework can be quite thin in some areas. The stone is vulnerable to decay, particularly high up where the flues gather and it is exposed to the weather.
A brick cross wall. Exposed by demolition of the neighbouring building.
Stone gable wall. Note the decayed stonework where the flues run.
Along with the skew, mutual chimneys form a firebreak between two tenements. Gaps in the wall inside the loft will allow smoke and fumes to escape into the loft and allow fire to spread to neighbouring properties.
Mutual chimneys share many of the repair issues that affect all chimneys, such as problems with copings, stonework, render, flashings, and pots.
Professional help recommended?
Although the work may appear straightforward, ensure your builder or tradespeople have the skills for the job. If in any doubt, get professional help to specify and organise the repair.
