Tejays Oven Build

[Tejaycar]

I'm not sure I'm putting this in the right place, but we'll start here. I've been dreaming of a wood fired oven for a decade or so now. Been reading these forums for most of that time, and feel like I finally have the money, space, and half the time I need to make it happen. So, here's my thinking. I'm going keep this top post as a place to chronical my plan as we go along. Hopefully this system lets me update my post as I go along. I'll use replies on my own post to actually ask questions and have a conversation. My hope is that will allow any future reader to glean the overall summary from this top post without having to dig through multiple pages of back and forth. We'll see how that goes...

So, here's the plan so far:
- 42 inch internal diameter hemisphere oven
- 88" square by 3.5" deep concrete hearth. This will be filled with a bunch of rebar and poured with a home mix of white portland cement, a TBD aggregate, sand, super plasticizer, and PVA fibers
- I'll also float glow aggregate and crushed glass in the top layer of this, and grind/polish the exposed areas to get a nice pretty counter top
- 64" square cinderblock base (note, this leaves 12" overhangs on all sides of the base, and puts the walls of the oven itself just inside the cinderblock base.
- I'll have openings on two sides of the base with a divider in between them. One side will be for the dog, the other for firewood.
- I also plan to put some bolts in the underside of the hearth to later mount brackets to. This will let me store my tools under the hearth
- 2 or 4 inches (I'm thinking 4) of insulation board under the oven walls and floor
- half brick dome sides (4")
- 3" of ceramic blanket and 2" of stucco finish
- I plan to put an air-gap (filled with door gasket?) between the inner arch and my chimney arch
- I also plan to do a semi-circle arch with "filler bricks" on the side. I saw this on another post and liked the control over airflow that it provided, as well as the better access when needed
- I'm working on a 3d-printed Indispensable Tool because it seems like the easiest way to go for what I want to do, and it appears to be a needed contribution back to the community

So far, I have poured the base slab, built the stand, filled half the cavities in the stand, framed out my hearth, and laid my rebar. I'm doing a few test pours on the concrete mix to get the color and strength my wife tells me I need.

[JRPizza]

Hey Tejaycar, welcome to the forum. Since this is a great opening post for a build thread I moved your post to the oven construction section. I do a little 3D printing so will be watching to see what you come up with for an IT. Stiffness is good in an IT so not sure how you will pull that off with filament.

[Tejaycar]

JRPizza My thinking is to print the hinge point and ends for both a brick bracket and a marker. Then connect the hinge point and ends with a threaded rod (metal) and nuts. So the metal rod will provide the stiffness. I'm also going to try to code up a brick cutting guide that will let you enter your angles and generate a wedge that can align bricks for cutting. We'll see how it goes .

[Tejaycar]

OK, so opening questions:
1. What firebrick should I use? I have local sources for Smithfield medium duty https://www.alsey.com/s/PDS-Smithfie...-Firebrick.pdf and Jet DP high duty https://www.alsey.com/s/PDS-JET-DP-H...-Firebrick.pdf From what I've seen, the medium duty is the way to go, but I thought I'd verify that with the wonderful experts here.
2. What's the latest thinking on insulating boards? Seems there are a number of materials, and I've had trouble keeping track of what the latest best options are.
3. Also, 4" of insulation, or is two plenty if I'm using the boards?
4. My biggest undecided design issue so far is how to handle the chimney area. I've not found any great posts yet on how to build out the base that supports the chimney, probably because I just don't know quite what to search for. I gather I need a front and rear arch, a opening between them, and somehow I need to make for a flat top. Then something?? to join that to the actual chimney. Any help on what to search for or links to good posts on the topic would be a huge help!


Thanks again for all the great help!

Oh, one more, what's the best way to attach photos? Doesn't seem to like google photos links, nor large photos...
https://photos.app.goo.gl/VtoR6LLF3MXgeTcw5
https://photos.app.goo.gl/arNsrmvB5zdq1qeA7

[JRPizza]

JRPizza My thinking is to print the hinge point and ends for both a brick bracket and a marker. Then connect the hinge point and ends with a threaded rod (metal) and nuts. So the metal rod will provide the stiffness. I'm also going to try to code up a brick cutting guide that will let you enter your angles and generate a wedge that can align bricks for cutting. We'll see how it goes .

I printed up an angled jig to cut my tapered arch bricks. Check out my build if you want to see it. I can share my model(s) too if you are interested. I use Freecad to generate my solids.

[jjnevis]

Oh, one more, what's the best way to attach photos? Doesn't seem to like google photos links, nor large photos...

If you have a Mac, then importing into Photos and exporting as jpeg medium quality, medium size works for me every time, sorry - not sure about other platforms, but keeping them medium/small will probably work.

[Petter]

Insulation thickness:

https://community.fornobravo.com/for...retic-apporach

I personally strive for a insulation thickness of 2-3 the brick/cast thickness. Everything else it either waste is wall thickness (i.e over all oven size) or wood consumption during heat up.

or in short:
5 cm is enough for cooking.
10 cm enables retained heat cooking.
15 cm is very good insulation.

[MarkJerling]

I'm not sure I'm putting this in the right place, but we'll start here. I've been dreaming of a wood fired oven for a decade or so now. Been reading these forums for most of that time, and feel like I finally have the money, space, and half the time I need to make it happen. So, here's my thinking. I'm going keep this top post as a place to chronical my plan as we go along. Hopefully this system lets me update my post as I go along. I'll use replies on my own post to actually ask questions and have a conversation. My hope is that will allow any future reader to glean the overall summary from this top post without having to dig through multiple pages of back and forth. We'll see how that goes...

So, here's the plan so far:
- 42 inch internal diameter hemisphere oven
- 88" square by 3.5" deep concrete hearth. This will be filled with a bunch of rebar and poured with a home mix of white portland cement, a TBD aggregate, sand, super plasticizer, and PVA fibers
- I'll also float glow aggregate and crushed glass in the top layer of this, and grind/polish the exposed areas to get a nice pretty counter top
- 64" square cinderblock base (note, this leaves 12" overhangs on all sides of the base, and puts the walls of the oven itself just inside the cinderblock base.
- I'll have openings on two sides of the base with a divider in between them. One side will be for the dog, the other for firewood.
- I also plan to put some bolts in the underside of the hearth to later mount brackets to. This will let me store my tools under the hearth
- 2 or 4 inches (I'm thinking 4) of insulation board under the oven walls and floor
- half brick dome sides (4")
- 3" of ceramic blanket and 2" of stucco finish
- I plan to put an air-gap (filled with door gasket?) between the inner arch and my chimney arch
- I also plan to do a semi-circle arch with "filler bricks" on the side. I saw this on another post and liked the control over airflow that it provided, as well as the better access when needed
- I'm working on a 3d-printed Indispensable Tool because it seems like the easiest way to go for what I want to do, and it appears to be a needed contribution back to the community

So far, I have poured the base slab, built the stand, filled half the cavities in the stand, framed out my hearth, and laid my rebar. I'm doing a few test pours on the concrete mix to get the color and strength my wife tells me I need.

Welcome to the forum. I look forward to seeing your project take shape!

[Baza]

Tejaycar ! Welcome to the forum!!
There are AMAZING people here to help you and many of them have already chimed in on your thread!
Check their builds out - they have chronicled the chimney assembly you are wondering about well with description and pictures!UtahBeehiver uses an approach I'm going to adopt (I'm at that point in my build too!).mongota uses another innovative way to level the space above the vent throat to transition to the chimney ... there are many more here - use the Search Function: Chimney base or something and you'll get lots of hits!

Your question of thermal material under the floor is a good one.
Many here (incl. me) used Calcium Silicate board - CalSi - apparently hard to source these days (what isn't!?) but the gold standard.
It is 2.5" thick and has great compression strength. I used one board as per Forno Bravo instructions ... It won't be bad - but I wish I used 2: for more thermal property AND height.

That is the next thing - think about how tall you are: make sure the height of your oven is roughly the same as your arm bent at 90 degrees (or so) - many say that is the ideal height - I thought I had it - but no.
More board underneath (or vermicrete - 4") works great - but do something! You don't want a heat sink!

Sounds like you are underway - I'm no master on this site - I've merely lurked and learned from others!

In all of this - have fun!!!
Looking forward to watching your build!
Barry

[mongota]

OK, so opening questions:
1. What firebrick should I use? I have local sources for Smithfield medium duty https://www.alsey.com/s/PDS-Smithfie...-Firebrick.pdf and Jet DP high duty
2. What's the latest thinking on insulating boards? Seems there are a number of materials, and I've had trouble keeping track of what the latest best options are.
3. Also, 4" of insulation, or is two plenty if I'm using the boards?
4. My biggest undecided design issue so far is how to handle the chimney area. I've not found any great posts yet on how to build out the base that supports the chimney, probably because I just don't know quite what to search for. I gather I need a front and rear arch, a opening between them, and somehow I need to make for a flat top.

Welcome to the forum! I have to say that when I built my oven, I had a lot of questions. If you're like me you'll find that once you start construction, everything sort of unfolds in front of you and the concepts you tried to grasp as a whole during the design process all start to make sense, one concept at a time.

1. I used medium duty brick.
2. I don't know what the latest thinking is, but I used ceramic fiber insulation. It was available, had been used by others, and is appropriate for this type of build.
3. I used two 2' layers (4" total) of board under the floor, and four 1" layers (4" total) of blanket over the dome, with two 1" layers (2" total) of blanket over the vent arch. My 4" of board insulation did get saturated during construction it dried out with no ill effects or loss of structural rigidity. I fire throughout all four seasons of the year, and typically get a 3- or 4-day cook from a single fire. I don;' see the need for more insulation, but I do think I'd be less satisfied had I used less. But that is based on how I use the oven.
4. I ran through myriad chimney designs, as well quite a few layouts on how to anchor the chimney. The solution I went with worked for me and my build, and it was fast, quite easy, and technically very simple to construct. I've had zero structural issues since completing my build. Probably easiest to link to the page of my build to show the chimney anchor: https://community.fornobravo.com/for...481#post406481

Enjoy your build.

[Tejaycar]

Thank you all for your input! I think I have a plan now for my vent, and I'm thinking 4-5 inches for the insulating board. I have a few products available locally, so hopefully we'll be in good shape. I know I've seen it in the forums, but I can't seem to find it anymore. What is considered a good compressive strength for the boards? By my math we're looking at single digit PSI in actual loads.

[UtahBeehiver]

70 psi @ 5% compression

[Tejaycar]

Thanks UtahBeehiver . My options are not where close to that . Any advice on where to find CaSi board locally (or online, for that matter). The local refractory places don't seem to carry it.

[UtahBeehiver]

Distribution International, branch in MO. Thermal Gold 12 is one brand of CaSi that DI carries. You can go with a 5 to 1 p/crete as well but it takes about double the thickness to equal CaSi. Most any refractory suppler will carry CaSi, it is not a big box store item.

[JRPizza]

JRPizza My thinking is to print the hinge point and ends for both a brick bracket and a marker. Then connect the hinge point and ends with a threaded rod (metal) and nuts. So the metal rod will provide the stiffness. I'm also going to try to code up a brick cutting guide that will let you enter your angles and generate a wedge that can align bricks for cutting. We'll see how it goes .

Have you checked out CapePizza 's build? I had forgotten that he did some 3D printed ends for his IT. Here is a link to his build with some shots of his printed parts
https://community.fornobravo.com/for...049#post429049