Widening chimney opening via a brick arch

We have decided to open up another chimney breast in the house (for a log burner, of course). We've thought about it for a while actually and now we are very lucky and fortunate enough to have a regular source of free hardwood, doing so means we'd be able to heat the home with two stoves. This means less demand on gas and the timber is a waste/byproduct of industry anyway.

As the other openings in our house show their original (rather modest) brick arches, I want to keep an arch in this room too. However -- I'd like the archway wider and higher up on face of the breast. I know it's possible but I'm hoping others on here can offer some advice.

The picture below shows the current state. As you can see, the opening has been bricked up at some point. I've halted opening up any more at the moment as there is a lot of debris coming down. Amongst that debris were a few live maggots, bird eggs, what appears to be soil, hair, string, timber. It's going to be a dirty job cleaning out so I am going to seal off the area with sheeting before carrying on. The 'columns' to the side of the opening are solid.

Can anybody answer my questions in the diagram below?

use a Strongboy centred above the new arch.
are you opening up to burner Mfr's min. dimensions? i should think so but i dont know of course?
stay away from the outside corners.
if you have an angle grinder then just cut down the marked lines for the opening - there's no need to remove any full bricks, just simply cut them or split them.
leaving in a full brick - 225mm - on either side is adequate.

bobasd said:

use a Strongboy centred above the new arch.
are you opening up to burner Mfr's min. dimensions? i should think so but i dont know of course?
stay away from the outside corners.
if you have an angle grinder then just cut down the marked lines for the opening - there's no need to remove any full bricks, just simply cut them or split them.
leaving in a full brick - 225mm - on either side is adequate.

Click to expand...

Thank you for the reply.

I've not used a Strongboy before. Am I right in saying you can use a steel support on the top which would slide in above where the arch would be sited? Might be a daft question if you're used to using them, but I presume I'd just remove a section of mortar then slid the support in and secure?

I'm not confident using a grinder so would need to employ the help of a friend there. I was hoping I could remove, resize and replace but understand this may not be recommended.

As for the opening dimensions, yes -- it will actually be wider than the minimum spec. by a good amount. The only reason I'm wanting it wider and taller is to make it more of a feature (as it's in the kitchen). We do have another burner I installed in 2017 but where I did not need to widen the opening.

I took the rest of the plaster off last night (as we want a bare wall) and dug out the rubbish left in the opening. I found a lovely old coal fire back boiler there with some thick, but soft pipes (tin/lead/steel?). Decided not to keep the arch for various reasons. Before I go ahead and order a lintel and a Strongbow, does the below look fine?

Blue denotes location of Strongboy and prop, red denotes location of new lintel and black denotes the extent to which I will be widening the opening. There will be a full brick width either side.

The construction of the chimney breast shows a single skin wall on the face, with two brick columns either side. I'm presuming the half brick width either side of the lintel is fine.

what you propose is fine.
the back boiler pipes might contain water esp if you still have a Cylinder?
no cylinder - then remove back boiler and cut the, probably lead, pipes off wherever it suits you.

wire brush off any soot
sweep the flue and smoke test it

Hi OP, I'm in a similar position to you re chimney rebuilding and I too have no experienceo using a strongboy but may have to. While I can't offer any advice I'd be interested to see and hear how you get on, so would be great if you could keep this post updated! Good luck

bobasd said:

the back boiler pipes might contain water esp if you still have a Cylinder?

Click to expand...

Thanks for your advice and help on this -- I know there are a million posts on it but some details weren't the same. As for the boiler, there's no cylinder at our house and I found the ends of the pipes cut off under the plaster work at the side, so proceeded to remove the boiler. The pipes were very easy to cut I think they are lead -- will be down the scrap yard for some beer money at the weekend I think!

Jimmy_103 said:

Hi OP, I'm in a similar position to you re chimney rebuilding and I too have no experienceo using a strongboy but may have to. While I can't offer any advice I'd be interested to see and hear how you get on, so would be great if you could keep this post updated! Good luck

Click to expand...

Cheers. I'll post updates on here of the project as a I go along. Local hire shop charges £6 a week for a Strongboy sand I've got the chimney sweep booked in next week. I'll start the building work at the end of the month.

The other install I did without altering the chimney construction is here: https://www.diynot.com/diy/threads/start-to-finish-woodburner-installation.492768/

Since completing it I've removed the plaster and revealed the original arch: