Building my first WFO using homebrew mix

[selmughanni]

Hello, I am now in the planning process of building my Pizza oven, I got so much useful information from reading the posts here, however I am struggling with an issue. I want to use the gym ball for my dome but not sure how I will be able to move the dome to the stand as it would be super heavy. Thinking about creating a dome from sand but it is not an option I want to work with. So I have been thinking, would it be possible to cast a layer of 25mm vermiculite: cement as a first layer to create a light shell then I can use this shell to cast my home brew mix over it? then continue with the rest of the insulation steps? another idea is to cast 20mm homebrew then move the dome and then cast another 30mm? Is that possible

[david s]

The sand mould method has the advantage of cast in situ, not having to move the casting with associated damage issues as well as seating and sealing issues at the base of the dome. Using a gym ball also requires the extra work of building form work around the bottom half of the gym ball.
Making the casting lighter by forming a thinner cast will result in a weaker cast more subject to damage, but you might be lucky and be able to shift it ok, or work out a method of multi sectioned castings. Casting a further layer on top of the cast in order to make it thicker may result in a poor bond with the risk of delaminating issues, but again, you may get away with it.

[selmughanni]

Thanks David, this really helpful!
I ended up casting on a ball and having someone help me left the dome on top of the hearth.

[david s]

Using vermiculite or perlite in the mix for the inner dome makes it insulative, less conductive, weaker and reduces thermal mass. Better to use a dense mix using either castable refractory or homebrew.

[selmughanni]

This what I have exactly done. For the bottom I used 50mm calcium silicate board. Then casted the dome with 40mm homebrew mix. On top of that placed ceramic blanket 2 layers with a total thickness of 50mm. Finally I did 10:1 vermicrete mix. Now I am waiting for the last layer to dry. I guess it will take a week or so then should I start curing fires?

Also after putting on the last layer I found myself in the situation where the front opening around the oven is not covered. How should I cover it? do I need plaster or would it need to be a homebrew mix. I am thinking to avoid any bricks to build the arch, just need a simple opening.


final question, when should I render and what material I should use?

I am really thankful for this forum and especially for you David where I used your advice in every step.

adding some photos below for the build