Oven Narcosi - Tunnel Oven Build - UK

[narcosi]

Hi Everyone - what a great forum, thanks to everyone who has posted so far for all their help. I have read for many hours and now i have a plan. I will use this forum to document progress add photos and also ask questions. Thanks for reading!!

Firstly i am British so i will be using the Queens good English so if you don't understand what render is and prefer weird words like: stucco then i apologise.

So here is my site: a raised herb garden where the herbs don't grow so they will now cook! As you can see its next to my outdoor kitchen.



Yes it is low down and i will get a sore back bending into the oven
Yes the tree may get a bit upset
nothing i can do about either!
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Here is my plan: - ish, well not really but it gives you an idea



Main points:
Tunnel shaped
Rendered finish over tunnel
Decorative arch to match bricks
Door
Flu

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My plan in more detail: as it stands today.

100mm (4") ish concrete slab
50mm (2") Ceramic Fibre Board
76mm (3") Fire Brick base
76mm (3") Fire Brick Walls
Pre-Cast Dome sections
Pre-Cast Dome Door sections
Stainless Steel Flu
50mm (2") Ceramic Fibre Blanket (i would like to double this if i can)
Mesh
Render
Some form of decorative arch in front - not sure how yet!

____________________________________________

Questions i have now:
1) Can i double to 100mm blanket or will it compress too much for the render?
2) Is it right for the flu to be just behind the door?
3) Should the flu start at a lower point than the roof to keep steam in?
4) I have seen people insulate between the oven and the front arch and even before the flu? why? should I?
5) I have seen flus above the entrance arch, outside the door - why? should I?
6) Should I use fibre board on the side walls rather than blanket?
7) should i join the side wall insulation with the base and put whole oven in a bubble? or is the loss of heat through the side of the base bricks not worth worrying about?
8) do i need to add anything to concrete - does it really need more insulation under it? I could pour on domestic kingspan or cellutex under concrete?
9) what do you think about the precast arches? is it worth me making my own from brick rather than using these?
10) I have a crap load of engineering bricks - can i use these at all for the base or any other part?
11) I have standard domestic clay bricks which you can see in the photo - i want to make the front arch from these? will that be ok? linked to question 4 - should i insulate them from the oven?
12) am i mad?
13) no seriously is there anything above which jumps out as stupid? the shape for example? straight walls? tunnel?

added after original post:
14) should i install thermocouples? if so where?

Thanks for reading and hopefully replying.

Jon


Likely source for most materials: https://shop.vitcas.com/
I will try to source some parts else where but i thought helpful for others to see where i am starting as UK supplies are limited.

Board: https://shop.vitcas.com/ceramic-fibre-board-insulating-board.html
Bricks: https://shop.vitcas.com/vitcas-fire-...x114x76mm.html
Mortar: https://shop.vitcas.com/oc-outdoor-oven-cement.html
Dome Sections: https://shop.vitcas.com/wood-fired-o...on-vitcas.html
Door Section: https://shop.vitcas.com/wood-fired-o...on-vitcas.html
Door: https://shop.vitcas.com/pizza-bread-...meter-500.html
Flu: https://shop.vitcas.com/chimney-flue...nd-damper.html
Blanket: https://shop.vitcas.com/ceramic-fibr...et-1260-3.html
Render: https://shop.vitcas.com/hps-heatproof-screed.html

[deejayoh]

Looks like a great location.

FWIW, I would suggest the following:
1) knock down the existing brick and build a foundation that brings the oven up to a better cooking height. Low oven will be more of a pain than you imagine. Even just to check the fire...
2) skip the barrel oven design. They are easier to build but don't generally work well and don't really save you $ on supplies.
3) in any case, the flue needs to be outside the door, not inside. If it's inside, say goodbye to all your heat (and the idea of a working oven)
4) yes it needs insulation, blanket on top and perl/vermicrete or CSboard underneath

Good luck!

[narcosi]

Looks like a great location.

FWIW, I would suggest the following:
1) knock down the existing brick and build a foundation that brings the oven up to a better cooking height. Low oven will be more of a pain than you imagine. Even just to check the fire...
2) skip the barrel oven design. They are easier to build but don't generally work well and don't really save you $ on supplies.
3) in any case, the flue needs to be outside the door, not inside. If it's inside, say goodbye to all your heat (and the idea of a working oven)
4) yes it needs insulation, blanket on top and perl/vermicrete or CSboard underneath

Good luck!

Thanks deejayoh -
1) i wish but just not possible, will cut all light from a window on the right you cant see. its this or nothing
2) so you propose a dome/round design? the barrel came really from the lack of width i have tbh....what particularly do you think is worse about them? anyone else view?
3) thanks - this is the bit which confuses me as so many pre-built ovens have the flu inside the door. Why would they do this? can you help me understand how its used outside? is it only when firing the oven with the door open? Does the flue having a closable baffle allow it to be inside?
4) yep plans for insulation are the thing i have spent most reading time on, i do prefer the rendered look rather than square surround hence wandering how much blanket to put under the render.

[mirassou]

Hi there Narcosi, you can read a thread about the differences between a dome and tunnel here:
https://community.fornobravo.com/for...dome-vs-tunnel

As Deejayoh said, I would seriously consider the height and look for another potential location if it's going to obstruct the window. Another consideration is the smoke and heat coming out of the chimney. If you have it that low it seems to me that you'd need a very tall chimney or you're going to be inundated with smoke when you start your fire. That tall a chimney would require additional support.

Here's a link to the FB store where you can download the Pompeii oven plans. That's how many of us started and modified them to suit our own creative desires.
https://www.fornobravo.com/store/pom...book-v2-0-pdf/

[deejayoh]

I might think about taking the tree out and turning the oven on a 45 degree angle so the entry is perpendicular to the angled section of brick. That will give you more room, and you can't really put an oven under the canopy of a tree anyway. that also solves your dome room problem

As for the door - those prebuilt ovens are rubbish. The way a pizza oven works, is - pulls in fresh air from the bottom of the entry arch, swirls around and gets super-heated in the dome, and then exits through the top of the entry arch into the flue. You can watch this starting to occur when you light your oven, and that swirling air is what cooks your food. Now, if the flue is inside the oven, then you basically have a fireplace. Air comes in, gets a little hot, and then goes out the flue. A closable baffle won't change things - that would just force the air out the door and into your face.

Good on you for doing the sketchups, but I would investigate placement and oven style a bit more before you pull the trigger on materials

[narcosi]

I might think about taking the tree out and turning the oven on a 45 degree angle so the entry is perpendicular to the angled section of brick. That will give you more room, and you can't really put an oven under the canopy of a tree anyway. that also solves your dome room problem

As for the door - those prebuilt ovens are rubbish. The way a pizza oven works, is - pulls in fresh air from the bottom of the entry arch, swirls around and gets super-heated in the dome, and then exits through the top of the entry arch into the flue. You can watch this starting to occur when you light your oven, and that swirling air is what cooks your food. Now, if the flue is inside the oven, then you basically have a fireplace. Air comes in, gets a little hot, and then goes out the flue. A closable baffle won't change things - that would just force the air out the door and into your face.

Good on you for doing the sketchups, but I would investigate placement and oven style a bit more before you pull the trigger on materials

Thanks and also thanks to mirassou - really appreciate the input. I hope you dont think my replies are not listening cause i really am, just limited in a number of ways.

i have read a lot on here and else where on the oven comparisons...i think i am comfortable with the tunnel. Having said that i would have probably chosen the pompeii if i could have done but i simply cant....this is the only location where i can install the oven. I am massively restricted on permission to build anything on my land....the tree is protected so i cant remove it. in fact it was my original plan to remove it and have more space for oven but not possible.

- How high chimney do you think i need? can i transition from brick to Stainless? Isnt a long chimney good for draw?
- Why can i not have the oven under tree canopy? is the smoke/air particularly hot? what sort of clearance do you think i need?

Any chance you guys could help me with any of my other questions also? thanks

[deejayoh]

Distance from the tree is subject to local regulations, but I know here in Seattle, an outdoor fireplace (applicable category) should be no closer than 15 feet of a structure or combustible material or vegetation. So a long chimney is good - but not if its poking through a tree. Gases coming out of the flue are hot enough to combust wood!

That said, I understand limitations! What is the substructure on the patio? hoping it is poured concrete

[narcosi]

Distance from the tree is subject to local regulations, but I know here in Seattle, an outdoor fireplace (applicable category) should be no closer than 15 feet of a structure or combustible material or vegetation. So a long chimney is good - but not if its poking through a tree. Gases coming out of the flue are hot enough to combust wood!

That said, I understand limitations! What is the substructure on the patio? hoping it is poured concrete

thanks again -

yes some things i have full control of and the patio is strong enough and weirdly i have hidden rebar under the flower bed to tie the concrete base into......
What do you think of putting extra insulation under the concrete - is there any point? i have some old poly and also some old celotex....also have to decide on 2" or 4" for FB on top of concrete.

Thanks for info about the tree i really hadn't thought about it - i will remove a branch which will be about 8ft above the chimney and cross my fingers for the rest - i read a chimney cowl was helpful in this case also. As for regulations - i tend not to allow such people on the property

[UtahBeehiver]

Since you decided to do a barrel or tunnel oven. You should look at Tscar's build, done very nicely. Play close attention to the buttressing he did and how he placed the end walls.

https://community.fornobravo.com/for...71-it-is-begun

[narcosi]

Since you decided to do a barrel or tunnel oven. You should look at Tscar's build, done very nicely. Play close attention to the buttressing he did and how he placed the end walls.

https://community.fornobravo.com/for...71-it-is-begun

thanks for the pointer really good read

[mirassou]

If memory serves me, I believe that the standard floor height is somewhere 40" If the oven is going to be below standard height, the flue will need to be that much higher in order to ensure that fumes and heat are well above your head.

Insulation below the concrete base is useless. Your ceramic fiber board will insulate the base of the oven and that will go on top of the concrete base.

I don't see where dimensions will prevent you from doing a dome. You could just make it smaller if necessary.

[deejayoh]

There's always the option of an ovalized dome, if you need it to be narrower

https://community.fornobravo.com/for...val-brick-dome

[narcosi]

If memory serves me, I believe that the standard floor height is somewhere 40" If the oven is going to be below standard height, the flue will need to be that much higher in order to ensure that fumes and heat are well above your head.

Insulation below the concrete base is useless. Your ceramic fiber board will insulate the base of the oven and that will go on top of the concrete base.

I don't see where dimensions will prevent you from doing a dome. You could just make it smaller if necessary.

Thanks, yeah dimney height will be interesting to set - i would like stainless (looks wise)
I had assumed it was pointless but i thought i would see if anyone though it was worth it as it was free.
As for the dome or even an oval, i think i am set on barrel now....roasting and bread is as much if not more of the value for me as pizza. Also wife prefers the look

[narcosi]

Hi all - making good progress with your help and other threads - i am updating my first post with answers for future builders

here are the most prominent remaining questions thanks:

4) I have seen people insulate between the oven and the front arch and even before the flu? why? should I?
9) what do you think about the precast arches? is it worth me making my own from brick rather than using these?
11) I have standard domestic clay bricks which you can see in the photo - i want to make the front arch from these? will that be ok? linked to question 4 - should i insulate them from the oven?
14) should i install thermocouples? if so where?

[narcosi]

Bump! would really like everyone's advice on some specifics. thanks