32 inch Pompeii Build

[JoJoMojo]

HEY HEY
This is My first Pompeii. I now know ( about 85% of the way done ) that i will build another.
I will try to add an album.
I am not a professional and everything i did, I researched and gave it my all.

I have had issues thus far.
I have some Questions regarding the dome rendering.

Question 1 - scratch coat, is that just home mixed mortar?

I mixed 1 part dehydrated lime, 1 part Portland cement, 4 parts mason sand.

That was my first render coat ( is this what they call a scratch coat? )

Question 2 - Is there a different coat/ mixture that goes on now/next?

I am getting a bit confused with Stucco finish, vs scratch coat / brown coat... ugghh.
I feel that if just put another layer on with the home mixed mortar, but lay off the lime?( take about a quarter of the 1 part lime out on second coat ).. it will be a bit stronger ?
then put a finishing stucco on that?

Question 3 -and what does everyone use?
lowes/homedepot stucco finish coat? Homemade mix?

queston 4 - does anyone know, If u use refractory cement over the base coat. would that be wise? or just stick to stucco when i figure all that out?

Thank you in advance for the help!

[JoJoMojo]

https://photos.app.goo.gl/bw61eottTZP36cPGA
THIS IS A LIKE TO MY PHOTO ALBUMN ON GOOGLE.. I CANT FIGURE OUT HOW TO DO IT ON HERE -_-

[Gulf]

Add the link in your signature

[Gulf]

Good! The Signature will only allow 1 line of text. You can cheat a little on that by linking words. If you look at my signature you will see my motto, a link to my photo album, and a link to my build here on Forno Bravo. If I used the entire links in text I would not be able to get all of that on one line. What I did was type "My Build Album", highlighted it, made it bold (the B icon) , and pasted in the link using the paper clip icon. The same with My Build, here on Forno Bravo.

[JoJoMojo]

Thank you sir, any recommendations on the rendering of the Dome? I insulated 2'' and covered with part lime 1 part Portland cement and 4 parts sand. a lil extra lime and cement for first ix and layer.
Please advise if this is ok to do.
I am still trying to learn as much about rendering that is can at this time. its getting cold and my time is running out !
I was thinking of getting refractory cement for the second coat then a strong stucco for the finish.
Am i on the right track?
or should i stick to the cement mix i used for first layer and lay off the lime and put more cement on second layer?
what did you use? for dome rendering?

[Gulf]

3" of ceramic fiber insulation is what we recommend as minimal. For extra insulation and to true up the shape of the dome, I installed a layer of vermiculite and portland. cement. It sounds like you are past being able to do that. For my outer shell, I used a bagged brown coat stucco mix for all three coats of stucco. I don't see the need for using refractory cement outside the insulation

[JoJoMojo]

Awesome
And yes, I only did two inches of ceramic insulation. I poured a key stone of refractory cement and covered a decent size of the top.

I had researched a good bit and did not have the space for the a few inches of vermiculite concrete around the dome. I was only going to do 1 inch of insulation and am glad i decided on 2'' now

humm, now i am wondering if the render i made will crack after curing?

[Gulf]

The fibers in modern stucco are supposed to limit the cracking. However, I do not trust it as an outer shell alone. At least not in a shell that is meant to perform as a roof. I included a rmesh wire in mine (not chicken wire) Much, like a ferrocement shell. Not easy, but anyone that is familiar with me knows that I don't do the many things the easy way . If you haven't, you may want to retrofit a vent near the top of the dome.

[JoJoMojo]

I plan on making the vent a good bit taller with some more fire brick ( ran out and only have 2 left ) so the convection is flowing well.
I look at your build its beautiful and detailed.
What exactly do you mean about retrofitting the vent at the top?

Do you think it would be wise to add a vermiculite and cement layer of about 1.5 inches on top of base coat i made??(1.5" - thats all the room i will have if i want to have an inch or so of a water proof layer of stucco too )

[Gulf]

It is not going to help anything by adding the vecrete outside the first stucco layer IMO. I should have used the term “breather vent”. I’m not at my computer at the moment but do a search of the forum using the keyword “breather”. That should bring up some threads explaining what I meant.

[JoJoMojo]

Gulf, I am now wayyyyy more confused on what a vent is or how it is to be installed or even the purpose ( except that it helps expel moisture during a curing process).
I had already put a small curing fire in the dome once completed and got it up to 300 degrees. I got a few small cracks around the dome. NOthing major, hairline, but enough for me to stop the curing process and do more research.
I hope I have not ruined my oven, as i continued after filling the small hairline cracks with firemortar. before installing the insulation.
Being my first oven, I imagine I have made some rookie mistakes, well i know i have, and starting the curing process too early was one. I will take it wayy slower once complete.

Do you think that my oven is compromised by 3 or 4, 6 inch hairline cracks with high heat mortar over them?

I am not sure I can install a vent now that the 1st layer of the dome is rendered?

if you could give me a beginner dummy explanation on the vent, i would appreciate it!
I am trying to research it now, but still am not really getting any explanation except that you can get it at auto parts and people do it for maintenance for the ovens.
I have not been able to find info on how to install, or how to not mess up the insall.
I appreciate you helping me this much already, I will continue to search about this vent thing

[JoJoMojo]

GULF! I found a few threads that have helped me understand what you were talking about, and i think its a great idea considering i have some small cracks to begin with.

Disregard last post. I was less educated than i am at this point.

is it okay to drill a small hole in apex of dome to insert the vent?
I do not want to structurally compromise any more of the dome.

After i get the 1/2 inch bushing set, and the second and third coat of render, does the valve always stick out? of the top? i have not seen this on any other ovens yet.
am i supposed to build the breather into the dome vent? maye run the vent to the center to do so?

plastic will be okay? would metal breather be a better idea? thanks again for info you provide!

[Gulf]

I'm sorry for confusing you. The vent/breather is just a hole in the dome shell to allow trapped moisture or steam to escape. It is thought that they are only important during the initial drying fires of the oven and anytime afterward that the oven has gotten wet or has been unused for a long period of time. It is usually placed at the apex of the dome. The hole should extend down to the top of blanket insulation. Though, many of us did, you don't need to think of it as something that you need to get from the autoparts store. But, it will need some method to keep rain from entering. The first one that I remember seeing was (I think) on cobblerdave 's build. It was a simple gooseneck shaped brass or copper pipe that threaded into a brass fitting that was embedded into the stucco/render. I believe that he removes the gooseneck when it is not needed and plugs the hole with a threaded plug.

There are other methods of venting the shell. Also, there are a lot of ovens out there without them. It is not a critical item IMO. However, I do recommend them. Good luck on your search. There are lots of discussions about them on the forum. I hope this explanation helps.

[Gulf]

Oops! I was writing a reply and eating lunch. I should have checked for more replies before posting.

[Gulf]

...........is it okay to drill a small hole in apex of dome to insert the vent?
I do not want to structurally compromise any more of the dome.

After i get the 1/2 inch bushing set, and the second and third coat of render, does the valve always stick out? of the top? i have not seen this on any other ovens yet.
am i supposed to build the breather into the dome vent? maye run the vent to the center to do so?

plastic will be okay? would metal breather be a better idea? thanks again for info you provide!

From what you described, you should have 2" of blanket under your stucco. Don't drill any deeper than through the first coat of stucco that you have installed. If you are uncomfortable about drilling the hole. Then don't. If you do, i wouldn't use a hammer drill. I would also place a depth gauge to make sure that I did not drill down any deeper than just barely through the stucco.

The bushing should not stick out above the stucco, but any type vent cover will have to be visible.

I don't understand the part of your question that I highlighted. Looking at my diagram and reading a few more threads should help.

A metal bushing would be fine as long as it has some type of rust prevention.