Removing Chimney Stack

[Louise C]

Hi, we recently purchased a 1910/20s semi with a redundant chimney that goes up through the centre of the house (breast removed at ground floor, steels supporting first floor upwards). Our survey flagged that this needed urgent attention as the render is visually coming off and bricks under are obviously badly spalled.
We’ve had a few Roofers out to quote and all want to remove the chimney stack down to just below roof level rather than repair.
Questions: what do we need to worry about with this approach? How does ventilation work? I would guess the remaining stack will need ventilation, but presumably I don’t want to vent warm air into the roof space! As it’s in the centre of the house, I can’t vent to an external wall.
Could we remove down to joist level and vent just in the first floor bedroom? Or would this require steelwork/supporting if we took it down that far?

Any help/guidance welcome. We naively thought it would be an “easy” repair job!

 

[Cubist]

It's not clear to me whether this chimney breast, and presumably the bulk of the chimney stack, is entirely independent of the neighbouring semi. Is this chimney breast/stack shared with the neighbour - in other words is there a single chimney stack exiting the roof of these semi detached properties? Do you have a clear and documented understanding regarding the extent of your and your neighbours ownerships, rights and responsibilities?

 

[Louise C]

Hi - apologies it wasn’t clear. The chimney stack/breast in question is entirely within our own property and entirely independent of our neighbour. We do share one with our attached neighbour, but that one is sound and doesn’t need repairing. (And for completeness, we have a third chimney on the external wall furthest from our neighbour also perfectly sound)

The one in question used to be for a kitchen range not on an external wall but also not on a wall shared with our neighbour.

Does that help?

 

[Cubist]

Thanks for the clarification. First you will need to check and if necessary seek approval from your local building authority if you've not already done so. The builders/roofers you have spoke with thus far appear to be trying the usual 'upsell' trick of suggesting more work than may be necessary or required. Assuming that the brickwork of the remaining chimney breast and stack through and above the roof is structurally sound - i.e. surface spalling damage only - then the minimum work that should be required would include removal of the remaining render and any lead flashing covering the tiles, mortar joint pointing and new render coating applied and lead flashing re-seated to prevent rainwater ingress to the roof space.

If you have no desire to see the chimney breast internally fully or partially removed then the above may be all that's needed.

 

[Flyfisher]

If you're happy to have the chimney stack removed to just below the roof line and terminate it inside the attic space, there are many types of almost invisible (from ground level anyway) tile vents through which the shortened stack could be ventilated.

Basically, reduce the stack below the roof line, cap the chimney opening but include some sort of ducting to a suitable tile vent to best match the existing roof tiles and rebuild the roof to cover the opening where the stack previously protruded. The stack would then be invisible but ventilated (though not into the attic space) and, with a good match to the existing roof tiles, the end result should be hardly noticeable at all.

This is likely to be a more expensive option than Cubist's suggestion though, so much depends on your budget and desire for the end result.

 

[alexander]

if the brickwork under the render is badly damaged then it will need replaced so far from having an up sell of the job required your having a quote for the easiest repair, if the chimney needs rebuilt then it is a lot cheaper and easier to remove the chimney rather than re-build then re render, the issue is if you drop it below the roof line you will allow hot air into the roof space potentially leading to condensation issues the only way to elevate this without reinstating the chimney would be to remove the breast down through all rooms, THIS of course would be a bigger job than a simple repair, but without looking at the chimney in question its impossible to say what would be the best solution.
good luck Alex

 

[Stevers]

if you drop it below the roof line you will allow hot air into the roof space potentially leading to condensation issues

That would be a good time to cap whatever is left of the stump under the tiles. An entirely redundant chimney in poor condition that cannot and will not ever be used again is a liability up on a roof.

We are up in a narrow valley completely exposed to sou'westerly gales, and I'm pretty sure we inherited only one tall original stone chimney because one had been blown over, and then rebuilt using stone from the other one that would also have been in poor condition.