My build, New Zealand.

[MarkJerling]

Winter pizza party.

[MarkJerling]

Hi Mark,

I've really enjoyed reading through your build and in particular using the storage heater bricks as this is a path I'm thinking of heading down. It sounds like you have put a lot of thought into your build so you may know the answer to my question - I'm trying to understand what goes into a heater storage brick that makes them different from a standard fire brick. From what I have seen online they add iron oxide to them which is quite bad for you in powder or fumes. But I assume because its set in brick that its not really an issue having food come in contact? Also, just wondering how yours are getting on? is your oven still out in the open? do the heater storage bricks rust at all?

Thanks,
Hamish

Hi Hamish

Thank you for your message. From what I have found online, they can contain magnesite or iron oxide. My floor bricks contain neither so far as I can tell, but as for the dome, almost certainly magnesite.
Most sand here contain a lot of iron oxide, so I'd be surprised if there's no iron oxide in some of the build materials. With the inner surface of the oven routinely getting exceedingly hot, I would expect that any off-gassing that may occur would have done so by now.

There is no sight of rust anywhere but the inside of the bricks are no longer a dark red, but more of a grey (for the dome) while the floor has remained a beige brick sort of colour. I'll check it with a large magnet to see if there's any bits that stick to the magnet and will get back to you!

I'll have to get back to you with whether the oven outlasts me or if I outlast the oven! I've not built any roof over it yet. I might do a pergola with a pull out awning.

Kind regards,
Mark

[Ham-ish]

Hi Mark,

I've really enjoyed reading through your build and in particular using the storage heater bricks as this is a path I'm thinking of heading down. It sounds like you have put a lot of thought into your build so you may know the answer to my question - I'm trying to understand what goes into a heater storage brick that makes them different from a standard fire brick. From what I have seen online they add iron oxide to them which is quite bad for you in powder or fumes. But I assume because its set in brick that its not really an issue having food come in contact? Also, just wondering how yours are getting on? is your oven still out in the open? do the heater storage bricks rust at all?

Thanks,
Hamish

[MarkJerling]

Hey Mark! Great build, hope you’re enjoying it during lockdown! I’m down in the South Island planning out a build. I’m trying to decide whether to build a roof or enclosure around the oven. I see you’ve just used waterproof mortar. Would you do it differently a second time? And have you put in a vent for the insulation? I much prefer the look of ovens without a roof or enclosure (and a lot easier/cheaper!) but worry moisture will eventually get in. Cheers!

Hi Dave

Only just saw your post, sorry! Lockdown has been fine as we have pizza! LOL
I like it just the way it is, but a roof will obviously be better for waterproofing. As it is, I think I'll paint the outside as some moisture still gets through the plaster. For the moment, I've found it best to cover the oven throughout winter with some tarps as it's only prolonged rain that is a problem. And boy, has it been wet of late!

Good luck with your project. Shout out if you have any questions.

Kind regards,
Mark

[DaveNZ]

Hey Mark! Great build, hope you’re enjoying it during lockdown! I’m down in the South Island planning out a build. I’m trying to decide whether to build a roof or enclosure around the oven. I see you’ve just used waterproof mortar. Would you do it differently a second time? And have you put in a vent for the insulation? I much prefer the look of ovens without a roof or enclosure (and a lot easier/cheaper!) but worry moisture will eventually get in. Cheers!

[MarkJerling]

Helps LOADS mate!
It really helps to visualize the idea and minimize what I was going to do! I had it in my head to build quite a buttress but the work you did is tight, focussed and apparently sufficient to the task.
I will move forward more comfortably with the idea of buttressing now.

Really appreciate your reply and photos, Mark!
Very kind of you!
Barry

Thank you Barry!
I look forward to following your build.

Kind regards,
Mark

[Baza]

Helps LOADS mate!
It really helps to visualize the idea and minimize what I was going to do! I had it in my head to build quite a buttress but the work you did is tight, focussed and apparently sufficient to the task.
I will move forward more comfortably with the idea of buttressing now.

Really appreciate your reply and photos, Mark!
Very kind of you!
Barry

[MarkJerling]

Hey Mark!
Been great following your build and your work on the heat tracking has been invaluable to the forum!

I'm interested in your Arch buttressing - you indicate that (like me) you have a segmented arch. You indicate you have buttressed the sides to support the assembly going up from there (your chimney is quite different moving backwards, but you still felt it important to buttress). I'm wondering if you have a pic to reference? It would be good to see how high up you went on the straight side of the segmented arch to ensure the outward thrust from any weight above the arch is compensated for in the buttressing.

I'm feeling I will have to factor in the same.

Thanks - and REALLY HAPPY FOR YOU with the success of your build - door, and particularly FOOD!
Barry

Hi Barry

Thank you for your kind words! Basically, you'll see that with the type of bricks I used, that I cut each brick in half to make my dome thickness. (Have a look at my build photos earlier in this thread)
But, for the lower part of the door arch, I used full bricks, effectively creating a double-wide support for the arch. Near the top of those "uprights", I also built out some bricks to act as a "hook" to hold the sideways thrust of the outer decorative arch, which is only a single 3" thick brick all round.

You can see what I mean in these photos. Notice the large "pillars" for the door arch:



And here, you can see how that "thick" pillar" on both sides does not go full height. After 5 courses I change to a thinner construction and you can make out the brick that "hooks" and holds the top of the front decorative arch from spreading sideways:



The photo is a bit dark but you should be able to make it out. The insulation layers and the plaster render hides that part of the door construction rather well.

In the end, I used a fair bit of mortar around the outer arch to give it more strength too:



Hope that helps!

Kind regards,
Mark

[Baza]

Hey Mark!
Been great following your build and your work on the heat tracking has been invaluable to the forum!

I'm interested in your Arch buttressing - you indicate that (like me) you have a segmented arch. You indicate you have buttressed the sides to support the assembly going up from there (your chimney is quite different moving backwards, but you still felt it important to buttress). I'm wondering if you have a pic to reference? It would be good to see how high up you went on the straight side of the segmented arch to ensure the outward thrust from any weight above the arch is compensated for in the buttressing.

I'm feeling I will have to factor in the same.

Thanks - and REALLY HAPPY FOR YOU with the success of your build - door, and particularly FOOD!
Barry

[MarkJerling]

Sorry, the size got reduced after I posted it. Trying again here. All the temperature charts are on the last tab of this worksheet: https://docs.google.com/spreadsheets...6dhTgi4oM/edit

Thank you, I can see those much better!
Very nicely done Craig! I wish I had thought of something like this!
Kind regards,
Mark

[lorenzo73]

Sorry, the size got reduced after I posted it. Trying again here. All the temperature charts are on the last tab of this worksheet: https://docs.google.com/spreadsheets...6dhTgi4oM/edit

[MarkJerling]

Very nice. Can you upload your image larger? It's tiny and impossible to read.

[lorenzo73]

Mark, your heat measurement fascinates me. How are you collecting this data? A thermocouple with a connection to ??? I'm a hobby computer nerd and this sounds like something I've overlooked! Beautiful door by the way, I'm looking to reach out to a fabricator family member to help create mine, but am stumped on what to use for insulation inside. Where did you source your stuff?

I mounted K-type thermocouples in the dome and floor, and connected them to a 4-channel readout that logs data to an SD card. I used this one (bought from Amazon): https://www.gainexpress.com/products/88598 ... Very helpful to have a record of each burn cycle.

[MarkJerling]

Very good advice. To that, I would add to consider using well-placed thermal breaks.

You're right. And, I could have done better with that on the door arch.

[MarkJerling]

Thank you so much mark this is very useful information... I really appreciate it... I plan to use my big cast iron Dutch oven inside the oven... part of my design is that big old antique beast need to fit inside... and I want to do large roast of meat as well...

one thing we do in Hawaii is imu cooking... below ground... Maori have this tradition as well... in fact for thanksgiving we did 4 big square tins underground.... we look at the wfo as an above ground imu that we can cook traditional Hawaiian food in.... I am thinking my original plan of 37 inches is on track... mahalo.

Yes, a Dutch oven works very well. We have one and it works great in the WFO.
You're right, Maori call below ground cooking "hangi" and I rather enjoy it.