38" vault in tropical Australia

[Onefella]

Well I've been working on my oven project for a couple of months now, so I thought I would post a couple of pics.

I have ended up doing my hearth slab a little unconventionally. I have a piece of cement sheeting as the bottom of my slab that stays in place with a network of stainless steel screws that will go through the vermiculite insulation layer on the bottom and will be embedded in the concrete of the hearth slab. The outside blockwork will end up with quite thick 'bond-beam' that will be at the same level as the hearth slab.

The monsoon is well and truly upon us now, and is holding up the hearth slab pour, but hopefully it will be done within a week, weather permitting.

[Onefella]

Re: 38" vault in tropical Australia

A couple more...

[nissanneill]

Re: 38" vault in tropical Australia

Hi Onefella,
with a name like that, you will have more once you get your oven finished and the traditional Aussie barby scene changes. Maybe you better reserve the name 'lots of fellas' when it happens.
Well welcome aboard anyway.
You will certainly need to weather proof your oven up there. Are you going for a dome or enlcosure type?
Do you plan on using it more for pizzas or baking, you know those Barramundi (Barra), Threadfin Salmon, Mangrove Jack, Mud Crabs, Queenfish, Giant Trevally (Jew fish), Red Emperor, Coral Trout, Spanish Mackerel, Longtail Tuna, Cobia, Black Jew Fish, Golden Snapper, Cod, Sailfish and Marlin.
All the best with your build and keep the pics coming.

Neill

[Onefella]

Re: 38" vault in tropical Australia

Hi nissanneill, heh, Onefella is a name of a local landmark, that I have adopted as my online name for forums and websites.

I'm going for a full enclosure including a covered 'porch' in front of the oven for when it's raining. I have always been interested in baking bread and that is primarily what the oven will be for. However years ago I constructed a large permanent 'Hangi' on a beach property we own (which is basically an in-ground wfo) that we use for large cook-ups with our friends. So the new 'above-ground' model will certainly be used for pizza and roasting.

lol, sounds like you've done a bit of fishing up this way? We will be trying various seafood, but we found that the hangi used to over-cook fish. But the oven should be easier to decrease the cooking time.

[Dutchoven]

Re: 38" vault in tropical Australia

I have ended up doing my hearth slab a little unconventionally. I have a piece of cement sheeting as the bottom of my slab that stays in place with a network of stainless steel screws that will go through the vermiculite insulation layer on the bottom and will be embedded in the concrete of the hearth slab. The outside blockwork will end up with quite thick 'bond-beam' that will be at the same level as the hearth slab.

Sounds like you are putting the insulating layer below the structural concrete slab...that was the way builders originally did it but we have found the vermicrete on top of the structural concrete will make a more efficient oven...otherwise that concrete will always suck heat away from the inside of your oven...I think you will be happier if you make a change now because it will be hard to reinsulate later
All the best to you!

[nissanneill]

Re: 38" vault in tropical Australia

Onefella,
I have only been to Darwin once for a week, stayed with friends at Rapid Creek and went out into the harbour over the WWII wrecks catching those great Jewfish. We occassionally get a load freighted down which is nice.
Are you working with Alan Scott's plans for the vault oven or are you building a Pompeii dome?

Neill

[Onefella]

Re: 38" vault in tropical Australia

Hi Dutchoven, ok, I'm a bit confused now, I thought the hearth slab was part of the oven's heat 'bank' and that it needed to be insulated. So you're saying the hearth fire bricks are the main source of heat for the sole and that they should be insulated from the hearth slab?

nissanneill, glad to hear you've 'hooked-up' on our monster jewie's. They're fun to catch aren't they? Yes, I'm working primarily from Alan Scott's design with a few elements from Rado Hand's design. Which is why Dutchoven's advice has thrown me for a bit of a loop.

[Les]

Re: 38" vault in tropical Australia

fella,

If you are building a Scott oven - you are most likely on a good build. From what I understand, you throw a butt load of heat at it and it retains it for a lot of baking. Most of us here are for a quick heat up, and with proper insulation, we can still bake the next day. With that said, we put our hearth brick onto insulation. Make sense?

Les...

[Dutchoven]

Re: 38" vault in tropical Australia

Hi Dutchoven, ok, I'm a bit confused now, I thought the hearth slab was part of the oven's heat 'bank' and that it needed to be insulated. So you're saying the hearth fire bricks are the main source of heat for the sole and that they should be insulated from the hearth slab?

nissanneill, glad to hear you've 'hooked-up' on our monster jewie's. They're fun to catch aren't they? Yes, I'm working primarily from Alan Scott's design with a few elements from Rado Hand's design. Which is why Dutchoven's advice has thrown me for a bit of a loop.

I built our home oven virtually the same way you are proposing in your post...if I had to do it over again I think I would rather build the "pompeii" design than the barrel vault...no more difficult or time consuming after building one of each...but regardless of that...the oven shape is not so much an issue as that of the insulating of the slab...true in the Scott oven and Rado's(who is incidentally a really stand up guy IMHO)the idea is to use that part of the slab as a "heat sink"...but...a very big but....it will take a really long time to fully heat that sink and unless you plan to cook for three days on one fire and not really get great pizza temps without firing for about 2-3 hours you will want to put the insulation on top of the structural layer...you can still lay the floor bricks on edge to get the 4.5 inches of heated mass from the floor...the cladding necessary in that design will give you a nice store of heat if you insulate it well and you will likely still be able to cook for a couple of days and then dry vegetables, fruits and the firewood for the next cooking day...
I don't mean to throw a cog in your wheel I am only speaking from experience
Best
Dutch

[Onefella]

Re: 38" vault in tropical Australia

Dutch, I hear you mate, and you have given me much to think about. I do have a bit of a dream to bake bread semi-commercially for our small town and I was resigned to long firing times for multiple bakes. I really appreciate your advice, but I think I'll still go ahead with the slab as part of the heat bank/cladding. (I hope this doesn't turn out to be too bad a decision)

[nissanneill]

Re: 38" vault in tropical Australia

Onefella

The worst that could happen IF you find that you made the wrong decision is "I told you so" from Dutch.
There' always plenty of firewood up there anyway to access, even if it is from the illegal immigrant boats!

Neill

[Dutchoven]

Re: 38" vault in tropical Australia

Dutch, I hear you mate, and you have given me much to think about. I do have a bit of a dream to bake bread semi-commercially for our small town and I was resigned to long firing times for multiple bakes. I really appreciate your advice, but I think I'll still go ahead with the slab as part of the heat bank/cladding. (I hope this doesn't turn out to be too bad a decision)

Onefella
OK I see what you are thinking now...my wife and I bake for a Farmer's Market out of our Scott/Rado oven...but we have constructed a pompeii style oven for our pizzeria/bakery...if you want more heat retention from the floor my suggestion would be to increase your floor thickness by possibly using a double layer of firebricks on top of the insulation...if you poor the structural concrete slab on top of the insulating layer you will still be heating that slab to it's outer areas(once again speaking from experience)including the block walls upon which it rests...I promise not to say "I told you so" but I am seriously saying I think you will be far happier if you put the insulation on top of the concrete and the oven floor on top of the insulation...we can find ways to get more heat out of it by setting floor bricks in that insulation...what was called an "island hearth" in the orignal pompeii plans...but they are still separate from the structural layer of concrete
All the best!
Dutch

[james]

Re: 38" vault in tropical Australia

I'm not sure I have have read your plans on this, but if you place the brick on the narrow edge, your cooking floor will be 4 1/2". That's a lot, even for a lighter use commercial bread oven.

Whatever you decide to do, insulate, insulate and insulate under the thermal layer (anything that will absorb heat, including concrete).

James

[Onefella]

Re: 38" vault in tropical Australia

OK guys, you make a convincing argument. I'll probably do it the way you suggest.

So you're saying that even with the "floating" slab design where the hearth slab only touches the base blocks by the reinforcing rod and otherwise is in no way contacting the rest of the oven; it still loses too much heat into the surrounding structure?

[Dutchoven]

Re: 38" vault in tropical Australia

So you're saying that even with the "floating" slab design where the hearth slab only touches the base blocks by the reinforcing rod and otherwise is in no way contacting the rest of the oven; it still loses too much heat into the surrounding structure?

If you are doing that floating slab you would be OK but that method seems to be a very complex way of doing it when it seems simpler to me to pour a structural concrete "tabletop"...then box out for the oven's footprint and our vermicrete to it...then lay floor bricks and build your oven...now that I understand a bit more about your design you will likely be OK either way...hope I have not been too long winded...all the best
Merry Christmas!
Dutch