My build in the UK

[stonejumper]

Thanks! Little update, just about 8 blocks to go into the top now. I wish i would of made the mortar myself so much easier to use than the ready bought stuff from Vitcas, the bricks held really well.

[UtahBeehiver]

If you do this, the best ratio is 5 to 1, any leaner does not give you the structural support, any thing less does not give you the insulation values. BTW, very nice joint work on the arch.

[stonejumper]

What type of cooking do you envision? I doubt you will see 300 C at the concrete hearth but it will draw heat away from the dome. If your cooking style is having a pizza party and then cooking something like roast the next day, then you are probably okay. If you want to do several days worth of cooking or baking lots of breads then you need to step back and evaluate your options.

Hi Russell,

Checked your Google Docs album, wowzers what a peice of art that build is!
I plan to do obviously some pizza and yes cook some roasts the next day, maybe some bread. I think I am going to notch the bottom row of bricks at about 45 degrees towards the end of the dome and fill with a perlite fill mix, I’m guessing it might get me 50% of the loss back? I've done far riskier things at work and got away with it. I’ll do 4 bricks at a time and fill underneath as I am going.

[UtahBeehiver]

What type of cooking do you envision? I doubt you will see 300 C at the concrete hearth but it will draw heat away from the dome. If your cooking style is having a pizza party and then cooking something like roast the next day, then you are probably okay. If you want to do several days worth of cooking or baking lots of breads then you need to step back and evaluate your options.

[stonejumper]

Silly mistake, not sure what i was thinking!? All makes perfect sense now. The top of the second brick on the outer dome is 20mm above the top of the floor brick, just for reference.
After reading quite a bit this morning concrete varies from not liking 300c to definitely failing at temps 800c.
My options
Leave it and risk it although i wouldnt be happy with the heat loss.
Point the dome up when complete down to bottom two courses and then cut out 50mm of bottom course to fit in more board, would take a while but i think it's definitely do able.
Any other thoughts?

[Chach]

Hi and thanks for the replies.
There is 50mm ceramic fibre board under the floor and arch but not the outer dome ring as i didnt quite order enough! the cement i've used is an outdoor oven cement made by a company called Vitcas in the UK, by the looks of it they are the main people to get oven supplies here. I have ordered another 20kg of cement but i think i will order a bag of powdered clay its not too expensive, thanks for the advice nearly went ahead and just did it. Glad i posted!

Not having insulation under the dome ring will wick heat from the dome which will transfer to your structural slab causing the slab to heat up as well when firing the oven. You may have to use more fuel as a result to get the oven up to temperature as your heating the slab as well. The structural slab is not designed for high temp use and may crack over time as a result. Your retained heat cooking more than likely will be reduced by a substantial amount or not exist at all.

Ricky

[stonejumper]

Hi and thanks for the replies.
There is 50mm ceramic fibre board under the floor and arch but not the outer dome ring as i didnt quite order enough! the cement i've used is an outdoor oven cement made by a company called Vitcas in the UK, by the looks of it they are the main people to get oven supplies here. I have ordered another 20kg of cement but i think i will order a bag of powdered clay its not too expensive, thanks for the advice nearly went ahead and just did it. Glad i posted!

[david s]

Hi,
Well underway on my first build now and really enjoying it, probably my favourite project I've done at home to date.
Quick question...
Can i fill the gaps on the outside with a perlite, lime, cement and sand mix? The mortar is ready mixed and quite expensive and i already have the other bits.
Thanks

You don't say what kind of mortar you have been using, but it is possible you are using an unsuitable mortar designed to sinter at far higher temperatures than your oven will see. If so you may find the mortar unsuitable. Do not fill the gaps on the outside of the dome with a perlite mix as will result in a mix with very low strength as well as having little thermal mass. A brew of 3:1:1:1 (by volume) of sand, portland cement, hydrated lime and powdered clay is a far stronger solution that also provides more thermal mass.

[UtahBeehiver]

Back mortaring the joints would be better using fireclay instead of perlite in a 3:1:1:1 ratio (sand, clay, lime, cement). Perlite is an insulator and will weaken the mortar mix. I cannot tell, it the dome wall sitting directly on the concrete hearth and not on any insulation? If so, just me aware, that the oven will lose heat as the dome heat will transfer down into the hearth. Also, what insulation is under the floor.? I know there is nothing that can be done you just need to be aware.

[stonejumper]

Hi,
Well underway on my first build now and really enjoying it, probably my favourite project I've done at home to date.
Quick question...
Can i fill the gaps on the outside with a perlite, lime, cement and sand mix? The mortar is ready mixed and quite expensive and i already have the other bits.
Thanks