How to Remove a Chimney
Removing an obsolete chimney breast on the ground floor is one of the most common internal home alterations. However, this often leaves just the roof void and the chimney stack in place. If the entire chimney needs to be removed, it’s important to get professional advice as building regulations will apply to the work, and planning permission may be required in some cases. The work may also be covered by the Party Wall Act of 1996 if there is a shared flue or other chimney structure to consider.
Gallows Brackets and Steel Beams:
To remove a chimney breast at the ground or first-floor level, it’s important to ensure that the chimney is adequately supported. This involves property supporting the stack, which is often done using gallows brackets. Gallows brackets are suitable for use if the stack is not completely vertical if the chimney breast on the other side of the party wall has not been fully or partly removed, if the party wall supporting the bracket is a minimum of 215mm wide, brickwork, and in good condition, along with other requirements.
Wherever gallows brackets are unsuitable, a structural steel beam or a beam and posts may be used as an alternative. You will need a structural engineer to submit structural calculations to justify the design and size of the steelwork.
Any steel beams or gallows brackets that are used should provide at least thirty minutes’ worth of fire protection unless they are completely contained within the roof and located above the ceiling. The best way to achieve this is by using two layers of 9.5mm plasterboard with a skim coat, or a single layer of fire-rated plasterboard.
Your Neighbour’s Chimney:
When removing a chimney, it’s important to consider that if the separation between the flues is damaged during the process, there is a possibility of dioxide or carbon monoxide leaks from the neighbour’s flue. Because of this, any brickwork in poor condition should be replaced and repointed and a smoke test carried out by a Gas Safe registered engineer.
What Not to Use:
Corbelled brickwork should be avoided since it will not be possible to provide a bond between the new and existing brickwork that has sufficient strength. It is also best to avoid timber bearers onto the existing ceiling or floor joists since there will be a significant point load passed onto the timbers, which creates a high risk of collapse.