DIY Tips & Advice
Proposal for supporting a chimneystack undermined on both sides Like many 1930s and 40s properties, our project house is semi detached with a chimney in the main front and back rooms on the party wall. Our chimneys share stacks with those of the adjoining property.
The neighbours have already removed their chimneybreasts and are supporting the remaining stacks on their side with gallows brackets. A large skillet of steel is placed under the cut-off stack, supported on what is really a heavy-duty shelf bracket. There are typically three brackets; one for each sidewall of the stack and one for the dividing middle wall that separates the flues for the ground and first floor fireplaces.
That the neighbours got there first, makes life a little more complicated for us, as we can't then use this simple option on our side. For structural reasons, we can't put brackets immediately opposing. However, a smart Building Control Officer suggested the following elegantly simple solution: move the brackets out wide of the chimney and place a steel across under the outside edge of the stack.
Moving the brackets out means they will not interfere with those opposing. Plus, they will be levering on the wall well away from the flues, where it is strongest (the wall is often thinner at the flues). The required steel is relatively short - so it can come up through the loft hatch - and does not need to be too heavy duty, since the span is relatively small.
Although a Building Control Officer proposed this set-up, it has yet to be approved by the officer responsible for our area. Unfortunately, you may have to pay a structural engineer to 'prove' its suitability in your case.
Short Steel and Gallows Brackets Support Method