28" ish Oven Dimensions

[mmonkeymann]

Hi

I want to build a pizza oven but I am limited to a base size of 1.2m hence I have decided to build my oven to the dimensions as shown. Do these seem resonable. I'm unsure about the door opening and the size of the flue. Any help would be very greatly appreciated.

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[turkey]

what materials are you planning to make this out of, and does the diagram include insulation?

re the flue you might be able to go down to a 5" flue possibly if space on the arch was tight.

with a limited footprint I suppose you need to decide what is more important cooking space , thermal mass or insulation, every inch counts and for pizza cooking you need little to no insulation really, if you only intend to cook pizza you could have thinner walls and less insulation, for bread you need thicker walls and more insulation.

there are the odd few on fb with small ovens, one is 26" I believe and the owner thinks it works for large pizza parties for him, so its totally possible to get a working oven I your space.

[pete123]

Hi good luck with the project.

Someone I met who had built 3 ovens suggested not going below 30" because the pizza might burn a bit at the edges. That said you could solve it my making slightly smaller pizzas. I'm sure someone with experience will post a suitable reply. I suspect others will have made 28* ones somewhere.

Pete

[cannyfradock]

Hello Monkeyman.......welcome to the forum

The smallest practicable oven I have worked is a 60cm clay oven.....



The hearth was very uneven but I still managed to bake about 40/50 pizza's in a 3 hour period for a community in the Taunton area.

Your 70cm oven diameter would be fine for pizza party's....and of coarse anything else like roasts or bread baking etc. My ideal size would be 90cm.....but people only ever bake 1 pizza at a time so 70cm would function perfectly for a domestic pizza/bread oven.

With your footprint of 1.2m this will still give you the space to add thermal blanket and vermiculite or perlite insulation.

The door opening sounds right for a 70cm diameter oven but I would push to get at least a 14" door. Any more than this and you may find it difficult to make the transition of dome to opening a bit tricky.

All the best with your build.....and please keep us informed.....

Terry

[tonyb]

When you say 1.2m is that square?The width of the wfo as per the drawing is only 920mm? Depending on whether you are using firebrick or pre-cast the 110mm thickness looks a little small to get good insulation.

[mmonkeymann]

Thanks for all your replies chaps. Love the clay oven Terry.

Sorry drawing is just the inner structural part. Have options of either ceramic fibre insulation or a vermiculite and cement insulation layer around this. Is the position of the flue particularity important, in terms of how close to the opening or the dome it is?

Was unsure whether to use some sort of castable or bricks to build dome. This decsion has been made as I have got 5 bags of some pre mixed castable. Its Cercast 1400, the instructions for it are here: www.budgetcastingsupply.com/Tech_Data/Cercast-3000-Mixing-Instructions.pdf

I was thinking of mixing it dryer than the instructions suggest, so that I can form it by hand over a sand mold in a similar way to how people do their clay ovens. Will it be ok to form the whole dome and opening section (to where I plan to build a brick entry arch) in one piece? Bit worried about it cracking.

I have some firebricks that are 3" thick that I shall use for the cooking surface. Unsure what to lay them on. Is a mix of 6:1 vermiculite to cement ok? What sort of thickness for this? Do you fix the firebricks down or just lay them loose?

Any suggestions on the cheapest way to make the base. Building over dirt, so I guess I need a foundation of some sort. Was thinking some dense concrete blocks on their sides. Then build the base up with aerated concrete blocks. Unsure at this stage how to do the top surface which will be under the insulation and oven floor.

Really appreciate all the help. I shall try to force myself to take some photos as I go along.

I'll bere in mind the size of my pizzas Pete, although don't want to get too premature yet.

Rich

[turkey]

with something like castable I would be reluctant to change its mix as I am unsure the part water plays in it setting so you could make it half strength or not even set at all depending how the chemical reaction goes. A sand form and flexible plywood outer seems a decent mould tho. I think one of the members here made a very good form and a very nice oven or 3 from it, it might be worth hunting down that post (s) to get some castable tips as I am afraid I don't know much about it.

under the firebricks you want insulation, I a using thermalite blocks layer flat but vermiculite cement will also do the job, the bricks are not usually perm fixed but a mix of 50:50 sand and directly to give a rough bond is used. These can be lifter out later should the need arise.

bases can be made in any which way really, we have seen builds that used metal legs to form a table of sorts or wooden beams used to make a frame. It all depends on the weight it will have to take and also the type of ground it is on, how long you need it to last, and the over all look. The most expensive part is usually all the concrete for a slab base and a cast hearth, if you could make a cheap base with just council grade paving slabs and then a light wall or internalize blocks you might be able to use lintels to support thermalite blocks and that would be direct up to your insulated layer to go under the over floor. Terry is doing a similar oven floor in his London build. You would need to fix the blocks well and make sure you had enough lingers to really spread the weight but I think would be perfect for a smaller oven really. Also very quick to throw up.?

just some ideas to start with

[cannyfradock]

Jun 19, 2012 21:00:00 GMT mmonkeymann said:

Thanks for all your replies chaps. Love the clay oven Terry.

Sorry drawing is just the inner structural part. Have options of either ceramic fibre insulation or a vermiculite and cement insulation layer around this. Is the position of the flue particularity important, in terms of how close to the opening or the dome it is?

Was unsure whether to use some sort of castable or bricks to build dome. This decsion has been made as I have got 5 bags of some pre mixed castable. Its Cercast 1400, the instructions for it are here: www.budgetcastingsupply.com/Tech_Data/Cercast-3000-Mixing-Instructions.pdf

I was thinking of mixing it dryer than the instructions suggest, so that I can form it by hand over a sand mold in a similar way to how people do their clay ovens. Will it be ok to form the whole dome and opening section (to where I plan to build a brick entry arch) in one piece? Bit worried about it cracking.

I have some firebricks that are 3" thick that I shall use for the cooking surface. Unsure what to lay them on. Is a mix of 6:1 vermiculite to cement ok? What sort of thickness for this? Do you fix the firebricks down or just lay them loose?

Any suggestions on the cheapest way to make the base. Building over dirt, so I guess I need a foundation of some sort. Was thinking some dense concrete blocks on their sides. Then build the base up with aerated concrete blocks. Unsure at this stage how to do the top surface which will be under the insulation and oven floor.

Really appreciate all the help. I shall try to force myself to take some photos as I go along.

I'll bere in mind the size of my pizzas Pete, although don't want to get too premature yet.

Rich

.....I've seen other builds where people have laid concrete blocks flat, then laid walls on top of them. Myself, I would lay a concrete base. if you lay a poly membrane under the concrete it can then double up as a dry storage space.

The vent opening goes outside the dome. I create a hole in the top of my entrance arch. I leave about 3" of the inner most arch, then create the vent so the flue has something to sit on. An ongoing build on the forum has created the vent directly outside the dome....I have also seen this method on the FB forum.

I've never used refractory concrete, but I can't see why it won't work using a sand dome. You will still want a couple of wet layers of newspaper on the sand before applying the castable. I believe that all modular ovens use re-inforcing mesh between a few layers of castable to prevent cracking. I would also build the arch first and create your sand mold around the arch, so as the castable meets the arch.

I do the same as Turkey.....lay thermolite blocks on flat, under the fire brick hearth .....again....I bed them using semi-dry sand and powdered fire-clay (50: 50 mix)

Cheapest option on the base is to use thermolite blocks then render the outside. Cast a concrete slab.....or use re-inforced concrete lintols.

Terry

[tonyb]

I don't recall any other builds casting in one piece, so you will be the first. Though at least one member Slowfood has cast his own wfo using moulded sections, hopefully he may be able to give some advice on using the castable ceramic material.