Do I need to buttress my side walls?

[Adamk]

First of all ( since this is my first post )I would like to thank all the people here for the knowledge they share.
Coming to my dilemma, do you think I might need buttressing for my wood oven ? The dome is 36” and I am planing on building a 3 feet round brick chimney with a 6” ss pipe inside using firebricks cut in half ( lengthwise ).
i would like to avoid it if possible mainly for aesthetics.. but I do understand there will be quite some extra weight on the two arches.
Looking forward to hearing your opinions..

[slschoming]

Welcome to the forum! It's a great community of expert builders (and novices like me)!

I was told that I should buttress my arch before building a masonry chimney. I was also advised to not use firebricks in any external application, as they soak up water more than standard house bricks. I do have some exposed firebricks in my arch and landing and I am hoping that it will be ok.. From your pictures it looks like you may not experience as many freeze/thaw cycles as I will in Kansas, USA so it might not be as big of an issue for you??

I hope someone with a little more knowledge on buttressing will answer your question, as you are planning on using bricks cut in half, so that will cut the weight in half as well.

[Adamk]

Thanks for the reply, in fact the WFO is being built next to the seaside where the temperature doesn’t really get below 0 degrees Celsius. Using firebricks outside can be tricky as you say as they absorb water easily ( maybe a sealer could help ). I wouldn’t mind using normal bricks but I can’t seem to find them in a matching color with the firebricks that is why I thought of using them. Now coming to the buttressing, the more I read on the forum the more i conclude that I should really do it, but how to do it Is another issue. I think I need to get some opinions from the experts as this is my first build and I am not very familiar with masonry, ( it’s a miracle I’ve got so far ).
And finally I think that i posted in the wrong section to start with! but I realized afterwards and I don’t know how to move my post that should be in the Pompeii oven construction ...

[david s]

The porosity of firebricks can vary quite a bit. I did a 24 hr soak and weigh on my firebricks and compared it to some solid reds I also had. The porosity measured exactly the same. It could be less of a problem than you think.

[slschoming]

Gulf and UtahBeehiver are both Member Moderators and may be able to help you move your post to the appropriate section. They may also have some good advice on buttressing.

I am thinking that adding one brick thickness would be sufficient buttressing, but you may need to pour a little bit of support under the landing and where the new outer walls will rest as it looks like your landing is hanging off the edge of your hearth. I am not sure how far forward your chimney will be, but I think you will want some more reinforcement under the landing if the front wall of your chimney will be flush with the front of your arch.

[slschoming]

The porosity of firebricks can vary quite a bit. I did a 24 hr soak and weigh on my firebricks and compared it to some solid reds I also had. The porosity measured exactly the same. It could be less of a problem than you think.

Good to know!

[UtahBeehiver]

If you were just install a 6" ss chimney, I would say you were okay not buttressing the side walls of the arch. That said, masonry chimney weight add us quickly and the configuration of the outer arch will see substantial sideward loading where the arch and vertical walls meet. You can accomplish buttressing by adding another vertical course butting up against the existing arch.

PS I moved the thread to the oven building section.

[Adamk]

Ok so do you think i can use the same firebricks to build these two extra walls in the sides ?( as I have some already ). And is it ok to build the line of bricks from half way backwards only ?( see photo ), because the rest of the structure is protruding in the front by half brick almost.
When I placed the last layer of bricks that support the arch I had this idea of putting some brass small rods inside for extra strength ( I hope that won’t be a problem with the difference in thermal expansion. Now I have the flue gallery and chimney base ready ( very similar design to the one of UtahBeehiver, thanks by the way for the great and detailed photos you shared of your amazing work ). I am going to wait before I start building the chimney around ss pipe until I figure out the buttressing. Finally is it ok to use the half firebricks build vertically or shall I look around for normal bricks? As David s points out the porosity is not such a big problem, maybe just the fact that they weigh more than normal clay bricks that’s all I can think of.

[Adamk]

I am not sure how far forward your chimney will be, but I think you will want some more reinforcement under the landing if the front wall of your chimney will be flush with the front of your arch.

I managed as you see from the photo above to make the base of the chimney so that is not completely flush with my front arch cause I wanted to be able to see part of the arch from the side.. regarding supporting it underneath I might figure out something but maybe it’s not entirely necessary as most of the weight is landing inside the hearth.

[UtahBeehiver]

In your original post, you said you were doing a 3 foot brick chimney. Based on the latest picture, the chimney is substantially shorter and topped with a SS chimney. I do not think you need to buttress now unless you feel you need too. The chimney load is substantially less than original envisioned.

[slschoming]

I am going to wait before I start building the chimney around ss pipe until I figure out the buttressing. Finally is it ok to use the half firebricks build vertically or shall I look around for normal bricks?

UtahBeehiver He is still planning to build masonry around the SS pipe. I think he will probably still want to buttress, but do you think his buttress walls need to extend all the way out to the front of his arch, or could he get away with stopping at the edge of his hearth? Look at the large picture in post #8 where he has outlined in red.

[Adamk]

I am planning to build around the ss pipe ( full length photo below ). While researching on the net I noticed that there isn’t a single WFO with a round brick chimney out there, so I was wondering is there a reason for it( complications on building it ) or just a matter of aesthetics?

[UtahBeehiver]

There are a couple spiral shaped chimneys that use standard rectangular bricks in the forum threads. I do not know the links but it is an advance brick construction technique.

[Chach]

Sounds pretty cool but pretty heavy at the same time pending how far up you go. Yes you would need to buttress the sides for sure.

[Adamk]

Ok, thanks a lot for the suggestions I will look more into it and try to make a decision about the design..