TechTalk: The Dangers Behind Using Gallows Brackets

“But gallows brackets were always fine” … no they weren’t.

Gallows brackets are a useful tool in any structural engineer’s arsenal but knock-on effects of on the structure around them means they are not safe for use in most chimney support scenarios.

For years gallow brackets have been used to support stacks where the breasts have been removed under. But now many Building Control bodies are refusing to accept these (e.g. Redbridge, Harrow, Richmond and many borough guidance notes) and with good reason – the bracket puts a bending moment into the wall resulting in a push pull that the masonry wall can rarely support.

“ Then why has there not been more failures?”  – This is simple: when removing a chimney breast on one side of the party wall, the push pull force exerted by the gallows brackets is resisted by the chimney stack on the other side. Any here in lies the danger…

If the neighbour later removes their chimney breast, then there is a risk of collapse. See the diagram above to help illustrate this. If there is chimney on the other side, like on an end of terrace property, the risk is even higher. See below photo for an example of this where the bending moment from the gallows bracket can cause movement and cracking in the gable leading to potential collapse if no remedial action is taken.

If you have existing gallows brackets in your property, please don’t hesitate to give us a call. We have carried out many projects where Gallows brackets require removal and replacement with a more robust solution. And if your builder insists on them, send them this link!!