Lining a truncated chimney and using twin wall flue for the roof penetration
It is quite common to find that an existing masonry chimney stack has been truncated so that it does not penetrate the roof. There may been many reasons why the chimney was truncated, for example the stack may have been in very bad repair and not in use so it might have been cheaper and quicker to simply remove the portion of the stack above the roof. The roof might have been replaced and it might have been decided that the chimney stack would not be needed. Whatever the reason for having a truncated stack it means that installing a stove is not quite as simple as it might be.
You would normally line and insulate the chimney with a flexible chimney liner right to the top of the stack, but of course the stack now terminates in the loft.
The solution is to line and insulate the stack to the top with a register plate at the bottom (as normal) and a fixing clamp installed into the masonry chimney to take the weight. The top of the stack should be made good and a flat surface provided for installing the anchor plate. The anchor plate lets you join the chimney liner to AKW twin wall flue pipe, and also takes the weight of the twin wall flue pipe.
From the anchor plate up AKW twin wall flue pipe is used to penetrate the roof and to rise up to the required height. Fixing and flashing components are available to make this easy for a wide variety of roof types.
For further technical advice, chimney and flue design and consultancy please contact us on 0800 246 1250
If you would like us to design your truncated flue system then please give us a few measurements and details on our truncated flue design form.
If you would like us to design your (non truncated) flue system then please go to the flue design service section of this site.