The Self Build Self Help Site Forming a chimney stack

A chimney stack, if not built correctly, provides a very good way for rainwater to penetrate the roof, resulting in water damage reaching down to the chimney breast in the living rooms. Once this state of affairs is reached it is very expensive to rectify.

The following series of photographs illustrate the process of constructing a stack, including some detail on preparing the lead apron and flashings.

Note. If a new build, your architect will have specified engineering bricks, if not, then ensure you use engineering bricks - do not use porous bricks.

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You may also be interested in building the chimney flues

photo of retaining wall in preparation

Stop the blockwork at the point at which it is just "emerging" from the roof. Complete filling the void around the liners with the vermiculite cement and level it with the top of the blocks. The liner has been cut to finish slightly above the blocks.

photo of retaining wall in preparation

A lead tray has been formed on a bench, a hole cut in the centre and a lip dresed up 50mm high. The tray has 3 coats of patination oil on both sides. The diameter of the finished upstand should fit it inside the chimney liner. The tray is domed slightly as the liner is cut slightly higher than the blocks - this will ensure any water flows outward. .

photo of retaining wall in preparation

The next liner has slits cut into it at the base and it is fitted over the lead upstand - any water going down the chimney will be channeled through the slits by the lead.

photo of retaining wall in preparation

The lead flashings are accurately measured, cut and formed before the application of patination oil.