Stability of a low vault design, when does buttressing becom a necessity?

[vitis]

Hi all

I'm new to the forum and currently building a 42'' oven with a low vault. Thanks to the Pompeii Oven Plans and this forum, most of my initial questions have been clarified, the oven stand is built and most materials arrived.
The only thing I haven't found a good answer yet: At what deviation from the spherical shape is buttressing of the dome recommended?

I've found some threads about "real" neapolitan ovens (with interior heights of about 12''), where a steel framework seems to be inevitable, but not much on the more spherical builds (maybe I didn't use the right search terms…).

Currently I'm planning on a middle ground interior height of 17.5'' (between the 15.5'' low vault and the 21'' high vault in the plans).
Planned is a walled enclosure filled with loose vermiculite, so no plaster on the ceramic blanket insulation.
Pictures for clarification.

Is there any experience whether such a design has enough inherent stability?
I'm toying with the idea of a steel cable bracing over the blanket insulation, but would not want to do it, if it would be complete overkill.

Thanks

[david s]

The Neopolitan ovens I’ve seen have a steel ring around the first course of dome bricks which are laid vertically (soldiers). I guess they only went to that trouble because those without the bracing failed. Part of the popularity of the hemisphere is that it doesn’t require bracing. Also cast modular low dome builds don’t have bracing or buttressing. The answer to your question of how much departure from a hemisphere or at what point would you need either bracing or buttressing is probably, build it, fire and use it for 10 years and see what happens.

[vitis]

Thank you for your feedback.
I was hoping that maybe someone from the forum has built a similar design or even the low vault as described in the plans without reinforcement.
In this case i will probably go for a bracing, even if it is just for my peace of mind...

[david s]

Try this build, I'm sure if you search this forum you'll find more.

https://community.fornobravo.com/forum/pizza-oven-design-and-installation/pompeii-oven-construction/431869-36-low-dome-neapolitan-style#post431869

[david s]

Sorry , this build is not a low dome, as it uses an IT with its pivot point at floor level. Getting the pivot point well below floor level is difficult with an IT. You’d need a different method for a low dome. Either building over a sand mould or using a plywood template are better methods for a low dome.