Looking for some feedback on 90 cm refactory castable oven build plans

[DavidLH]

Hi. I'm planning to construct an outdoor pizza oven mainly for neopolitan pizza, to upgrade from my Roccbox. I don't really have the tools for cutting bricks, so I thought about making the oven over a sand mould/pile with refractory castable. I've read a few post and watched a few videos on diy oven construction and came up with the attached plan. I have no experience, so any feedback on the plans (materials/dimensions/etc.) would be much appreciated. I want to be sure that this setup will be able to get hot enough to cook pizza in 60-90 seconds. Plan is attached as a photo. Thanks in advance.

Edit: for some reason the upladed picture is bad quality, here is a link to a higher res version https://i.imgur.com/JOfEJXV.png

[UtahBeehiver]

I took quick look at the PNG file and a couple comments. The chimney vent seems too small for the oven size, based on 90cm (35 inches +/-) the chimney should be a min. 6 inches internal diameter. I am not sure what you mean by ceramic isolation plates, are we talking Calcium Silica board or something else, do you have any specs on this material? Castable refractory needs to be dense and not insulation type. David S is our residence casting expert so contact him. He may also suggest SS melt extract fibers for the casting material.

[DavidLH]

Thanks for the tips. The ceramic isolation plate I'm planning on using are these (In Danish, sorry) (https://www.ildfastesten.dk/keramisk...iberplade_50mm). And this is the castable https://www.ildfastesten.dk/ildfast_...sse_1400C_25kg. I'll make sure to get a 20 cm chimney instead of the 10 cm one.

[UtahBeehiver]

I am just guessing on the specs since I do not read or write Danish but the 0.08 k value (thermal conductivity) is right in line with CaSi. The only other thing to check, which I did not see is the compression factor, should be min 0.5Mpa or abt 70 PSI. On the castable, just need to make sure it is the dense version not the insulated version. Look up DavidS posts, he is our cast expert.

[Shaunster]

Im in the process of building a cast oven in the UK, nearly finished now but this thread on here really has a lot of good info. https://community.fornobravo.com/for...sted-over-sand

[david s]

If you check the data sheet on the castable product, it’s density should be in the region of 2000 kg/m3 which is the same as kg/1000 litres. That is 2 kg/litre (don’t you love the logic and simplicity of the metric system?)

As Russell suggests a 6” (150 mm) flue Pope is required for a 900 mm diameter oven.
The deep tunnel in front of the oven will make operating it difficult. Better to make it shallow. A separate flue gallery that is outside and in front of the oven chamber is a superior design well worth the extra effort, improving both circulation and performance, as well as increasing retained heat cooking times whilst reducing heat loss.