Rebuilding stacks (a mindbender)...

[paulb33]

Sorry for the lengthy post. Folks have been kind in responding to numerous posts about our restoration. Well, our 1901 arts & crafts house is now shrouded in a ruinous quantity of scaffold. I stood next to the chimney-stack yesterday. Weird how this was so thrilling. I must get out more….

Anyhow, I'm puzzling about rebuild of the main stack. I only have the original architect's watercolours to go on. Also, the size of the base that remains.

I've attached a draft scale drawing of the stack that an architect knocked up a few years ago. Also, a photo of the chimney stack base and the original architect's drawing (showing the stack in all its glory).

The restored chimney will likely consist of two 2240mm tall offset square stacks made of imperial (230mm x 73mm) bricks standing on a 1300mm x 800mm limestone base. This limestone base will sit on the 1165mm x 675mm imperial brick base that is currently in situ and capped at second floor level. The chimney would be visible from the road as two diamond shaped brick stacks.

One thing is puzzling me and the drawing doesn't address it: how doed the two stacks sit or tie together?

The size of the base (1165mm x 675) means that two stacks made of two imperial brick widths (230mm x 73mm) with 5mm mortar would be too wide for the underlying brick base that still remains. So, I've concluded that the stacks must probably interlock somehow. But, I can't for the life of me work out how the brick interlocking between the tacks would work and ensure bonding. I've even made paper bricks to model this bonding, but without success. There's always two mortar joints lining up on adjacent courses. Doubtless I'm missing something very straightforward.

Perhaps cut-down bricks are used? But, that wouldn't seem a very elegant solution for stacks that are clearly two brick lengths in size.

Who has the brainpower/brick experience/patience and is kind enough to help to solve this riddle?

Regards,

Paul

 

[88v8]

As you say, two standard 18" stacks with 9" flues, but interlocked diagonally... hmmm, lacking a pile of bricks to play with, don't see how to do it without using a lot of closers.
I'll have a rummage through an old book later. If I can find it.

Ivor

 

[stuart45]

You can mitre the bricks where the stacks meet, and put in some ties for extra bonding.

 

[paulb33]

Now you mention it, Ivor. The whole house is built with many small and odd sized bricks. Is this what you mean by "closers?" So, maybe that's how it was built?

Seems like a lot of trouble to go to and rather odd to my untrained mind/eye. But, perhaps its a characteristic of the arts & crafts/edwardian freestyle approach? Namely, one that builds with a focus on 'honesty' and 'integrity' of the build? Meaning that size of walls (and thus, room size, chimney stack size, etc…) was dictated by function of the rooms, rather than constrained by brick length????

Perhaps I'm stretching this a bit….. I confess that I was trying to find an approach to the stacks that was divisible by two imperial brick lengths. Maybe I shouldn't be constrained in that way..?

Grateful for an other pearls that you might offer…

P

 

[stuart45]

A closer is a cut brick, such as a Queen or King closer to make the bonding work.
The majority of bricklayers wouldn't even bother to mitre the bricks where they join, but just stick in some ties.
However if you want to show no straight joints in the corner mitre half the brick at 45 degrees where they meet.

 

[plasticpigeon]

If you had the bricks where they cross over laid at 90 degrees to each other one on top of the other, so that they formed a cross from above there would be no straight joints where they met. There would be 1/4 brick sticking out each side of the cross. It might make the bonding on the rest of the chimney a bit awkward.

 

[paulb33]

The chimney below is a local house by the same architect, built around the same time. It helped me to deduce that the original stacks were most likely two offset squares.

This chimney seems to be built from squares that are exactly two brick lengths. This was driving me towards using two brick lengths in mine. Also, daylight is visible between the stacks suggesting they're not interlocked. Instead tied at the top?

As I mentioned above, the size of the remaining base limits the size of the stack. Perhaps my original chimney stacks were built from smaller imperial brick lengths, in order to fit on the plinth? So, I could just simply use smaller bricks?

Am I making this harder than it really is????? :roll:

 

[paulb33]

If you had the bricks where they cross over laid at 90 degrees to each other one on top of the other, so that they formed a cross from above there would be no straight joints where they met. There would be 1/4 brick sticking out each side of the cross. It might make the bonding on the rest of the chimney a bit awkward.

I think I tried this with paper bricks. It left me with a bond problem on adjacent layers.

I'm grateful for your further thoughts on this...

 

[stuart45]

This pic may help. The only straight joints visible are on the inside of the flue. This would be the standard method. A rule of thumb for 1/2 bond walls is that nothing less than a half brick should be on the face. There are some exceptions for corbelling.

 

[paulb33]

This pic may help. The only straight joints visible are on the inside of the flue. This would be the standard method. A rule of thumb for 1/2 bond walls is that nothing less than a half brick should be on the face. There are some exceptions for corbelling.

I think you cracked it, Stuart! I'm embarrassed to say I've puzzled about this for over a decade! Just need bricks and a bricky now! Thanks so much.
Paul