32 Inch Cape Build

[CapePizza]

When do you "retire" (stop using) the IT? I just completed row 9 which left the dome with an inner diameter of 9 inches. I could probably lay one more (maybe 2 more rows) using the IT. But the other issue is the interior of the dome (measuring to the bottom of the bricks on the just completed 9th row) is just about 16 inches in height (which is what the finished dome should be for a 32 inch oven). If I keep going with the IT, the interior would wind up being about 16 1/2 to 16 3/4 inches. Probably not a big deal.... but I guess what I'm asking is there a rule of thumb when to put a platform in there and use that as base to install the remaining brick rows off from? Thank you for the help!

[Ope-dog]

Hi John,

I know that many folks here have talked about the dome height and the IT as you get close to closing. UtahBeehiver really has a good grasp on this concept and many folks will advocate for an adjustable IT to compensate for the very issue you describe. Thank you for asking the question as I have played out this scenario in my mind on more than one occasion as I gather my build materials and finalize designs.

It seems the math dictates that your pivot point would have to be at dead-zero floor level to maintain the 16" dome all the way. But most ITs probably are not at a flush level and thus you end up with some compounding measurements as you increase your angle.

But to echo others.. your build really is top-notch. A good looking oven for sure. And as others have also said.. your perfectionism probably won't allow this, but that .5" or so difference will only be noted by you in the end.

[CapePizza]

Thank you for your kind words, Ope-dog. I appreciate it! I'm not too concerned with the interior dome height being a bit taller than the 16 inches. I'm just not sure whether I want to switch from using the IT and go to the plywood disc quite yet, or at all. I'd rather be able to see how the bricks are lining up on the interior and using the plywood disc method would make that problematic. I have an adjustable IT, but at this point, lowering it a bit, will leave a lip on the next row ( as the bricks in that row will be lower by the amount the IT is lowered) One thing I was thinking of doing is making a new IT attachment that is kind of offset. What I mean is kind of tilting the portion where the brick rests by maybe 10° so the bottom of the brick lies more parallel with the floor. And then the IT can be lowered a bit. The brick may need to be beveled on the back side so as not to leave so much of a mortar fill. See attached. Anyway, still thinking about it all. If anyone else has any thoughts about this or switching from using the IT to the plywood disc and car jack method, I'm all ears. Thanks very much.

[UtahBeehiver]

I made a smaller "L" bracket and used it if combination with notched sticks. A 0.5" increase in dome height will NOT make any difference. Move on and don't worry about it.

[Kvanbael]

my 2cents:

About that stage in my build I switched to half bricks in “soldier” orientation. As they are a bit taller I only needed one course before I could fit the keystone (and it coincidentally Required the same # of bricks as the previous course, avoiding aligned joints). As I had the bricks tapered in advance, it took less than two hour to place them, cut and place the keystone. After which I could remove the supporting disk and clean up the inside mortar.

[Neil.B]

I tried the disk and sand method but didn't like not being able to see the joints. I laid one brick then took it out and went back to doing it without support.

[Chris inPA]

It's looking beautiful so far. Nice clean lines and your course lined up perfectly w/the inner arch.

On your previous questions about the gaps: I personally did a lot of extra cutting and grinding to keep the gaps as small as possible. It took a lot of extra time, and wasted a ton of brick. I had about 5 of the 5 gallon buckets full of scrap when I was finished with all of my extra cuts. That's a lot of wasted bricks. And in retrospect totally unnecessary. My thought process was: use more brick = using less mortar = greater thermal mass and less mortar to ever deteriorate.

If you ever go on the Facebook forums you'll see some of the ugliest builds ever. When I saw some of those I totally relaxed and was instantly less critical of myself. Your build really is turning out beautiful.

[CapePizza]

Plugged the dome today! Happy! Good feeling!!

[Neil.B]

Congratulations John, I'm so happy for you. Looking forward to your vent/chimney design.

[CapePizza]

Question about heat break around the arch. I'm planning on creating a recess around the outer arch bricks where they meet with the inner arch opening bricks. This is similar to what I've seen others do, so a typical kind of set up. I'm planning on using 1/2 inch ceramic rope and stuffing it in the recess and covering with PCrete. My question is..... if the chimney bricks get mortared to both the inner arch and the outer arch bricks, does that kind of negate the purpose of the heat break? If there's going to be expansion going on due to the heat, even though the outer arch is not linked to the inner arch(due to the recess stuffed with the rope), the mortared chimney bricks where they contact both inner arch and outer arch do create a fixed brick situation. Does that present an issue (like possible cracking)? Thanks in advance for any comments/insights/thoughts!

EDIT: Or maybe the ceramic rope heat break is there more to prevent loss of BTUs to the outer arch and entry floor landing? thanks

[Kvanbael]

No it doesn't negate the purpose of the heat break (which is to retain heat). You want to insulate the inner dome and limit the thermal bridges to the outside parts. Your chimney connection would be such a bridge. But it's fairly local, so heat loss will be limited.

However, your implementation of the heat break is also like an expansion joint: You have 2 large rigid constructions at very different temperature, connected by only a few bricks on top. There will be shear-forces and that mortar joint will fail. I also have heat break but my chimney is only connected to the outer arch.

Curious how others dealt with this. Maybe you should dry-stack that particular joint. I would even consider a layer of CalSil in your case (assuming your final rendering will cover all of it.

[CapePizza]

Thank you for your thought, Kvanbael. I think you rephrased my question in a way that I meant to say it. If you've got the chimney mortared to the outer arch bricks AND mortared to the inner arch bricks, that seems to me it would present an issue negating the heat break. So I guess my question is, as you say, should the chimney bricks that overlap the inner arch bricks just be dry stacked and not mortared to those inner arch bricks? and.....just mortar the chimney bricks to the outer arch bricks?

[mongota]

Do you not have enough space to make your tunnel slightly deeper so the chimney can rest solely on the tunnel, instead of on both the dome arch and the tunnel?

When I made my tunnel, I cut an "L" in the dome arch end of each landing tunnel brick so they could wrap around the dome arch brick. I also used 1/2" rope between the two.

The interior depth of my tunnel was 1-1/2 bricks, or 13-1/2". The exterior depth of my tunnel was slightly longer, maybe 14-1/2", due to extra inch from the leg of the "L" in the wrap-a-round cutout.

That extra length allowed my to fit my chimney transition on top of the tunnel without it touching the dome. My transition to hold the chimney anchor plate is six firebricks on edge deep, mortared together, so roughly 14-1/2" deep. A perfect match for the 14-1/2" exterior depth of the landing tunnel.

Confusing even when I type it, maybe the attached photos will help? Not the best shots, but hopefully they'll clarify my text a bit.

Based upon my oven? Because of differential thermal movement, I would want the dome to be structurally independent of the landing tunnel.

[CapePizza]

Thanks for the feedback, Mongo. Since I posted that last question , I came to the realization (and with the advice of another helpful WFO builder) what you're describing is exactly what I need to do. Keep the chimney structure a separate entity from the dome. And believe it or not, I have screenshots of those same pictures you just posted sitting on my desktop for reference. So thanks again!!

[Baza]

CapePizza I have those same shots saved too - believing in the importance of keeping the vent separate from the arch/dome.
I'm glad you raised this question as I'm on this part of the build now too.

I think I may have goofed in creating a similar sized landing as Mongo's without compensating for the overlapping lip piece Mongo shows in his photo.
Utah looks like he cut a tapered back brick that met with the Dome Arch face, put rope in and mortared it in place - but that brings us back to your original question (again, glad you asked as I had/have it) it ties the two structures together. Wonder if he experienced cracking/issues with his approach to the break that included rope and mortar?

In any event - your build and questions are very helpful
Congratulations on the progress of your build - looks terrific!
Barry