side opening barrel vault

[geoffisegwr]

Hi there,

First posted on the introduction thread, but thought this might now be a better place to continue posting.


After spending many hours (or days according to the wife!) trawling through the forum, i've finally decided to come out and say hi and share my build.



First of all, many thanks for everyone that's contributed to this forum, it been a terrific source of information.



As you can see from the photos (hopefully uploaded ok), i eventually opted for a non-conventional vault/barrel oven which has a side entrance. I was a bit limited on available depth so decided to utilise available width. To give an idea of scale, my hearth measures 84x57 cm. I've tried to match the dimensions of some of the modular ovens, so hopefully should be ok. I'll update this view when i start using it.



I've know finished the thermal break between the arch and the dome using cut sections of thermal insulation block (1 to 3cm thick) and then fixed/sealed with
homebrew. I've created a base for the chimney and this is where i am after some advice/suggestions.

As far as the chimney, one idea was to fashion a base plate using some left over thermal block then attach one of the rectangular clay flue liners. 

First question - can the thermal blocks take the heat and is there a optimum chimney height ?  Is there specific width (opening) to height ratio ?

Next issue is insulation. I over did the oven a bit and now i'm a bit pushed for space on the sides. I need to try to minimise the thickness of the insulation. I gather form some of the earlier threads that one way of doing this is by marginally increasing the blanket thickness and thus avoiding the recommended vermicrete thickness. Does anyone have any updates on this approach ?

If this is approach is still good do you simply apply the render to the blanket (covered with mesh) or do you need a 'stiffening' layer ?


Apologies if these questions have been answered before. 

Looking forward to any comments, suggestions, critic and the odd sharp intake of breath.



Thanks

[cobblerdave]

G'day
The thermal block if it's cement based I'd say no. Cement started breaking down at temps of 300C . That's why the homebrew has lime to provide the long term heat proof " glue in the mix.
The ceramic blanket is stiff and hard to compress and can be rendered over. 2 inches of blanket is s good standard. The pearlite cement mix is an extra to the insulation required and just used just to even out the lumps and bumps. I rendered Over 2 ins of ceramic and then 3 ins of rockwool no problems.
Hope this helps
Regards dave

[geoffisegwr]

Hi Dave, thanks for response.

I guessed that the thermal blocks wouldn't be suitable but thought i'd put it out there to see. I probably go down the shaped fire brick route as seen on one of the other threads.

One thing i forgot to ask last time was, are calcium silicate boards more efficient than the blanket ?

Can I assume that if i cover the boards in foil (similar to under hearth insulation), I render directly on this ?

JT

[cobblerdave]

G'day
Wow never thought of using board to cover an oven as I mainly deal with dome ovens. But will silica board bend enough to wrap over your arched vault oven is the question?
As for performance myself I recon it would be so close you would probably not notice the difference.
Not a big fan of aluminum foil in oven construction however. Corrodes to easy out of the open air where it normally sets up a protective layer of aluminum oxides. In the presence of water the lime and cement effect it too. Take a piece of kitchen foil and put a brick over it on your lawn, leave it for a week. The foil in the oven air should fair alright but the piece under the brick will start to corrode.
Regards dave

[geoffisegwr]

Hi Dave, 

thanks for the foil info.

With regards to the boards, i was only considering  using them on the sides of my oven, where i have a flat face. I will go for the blanket over the dome section.

cheers

JT

[moonhead]

Hi JT,
I used a large chunk of cal sil board at the back of my vault oven as I had ran short of blanket. Covered in wire & vermicrete and has caused no problems 2 years down the line.
Good looking build look forward to the finished oven.
Rick

[geoffisegwr]

Hi Rick,

Thanks for that info. I've been dithering a bit about the insulation, but probably heading down the integrated approach using a bit of everything.

I just need some free time to get on with it.

cheers

JT

[geoffisegwr]

Finally got round to adding the chimney - i used 2 sections of clay cavity wall liner (not quite a conventional flue liner but hopefully should be okay)

I'm mid way through the initial firing process and all seems okay - there appears to be a good draw on the chimney

Looking forward to cranking it up on the weekend.

[cannyfradock]

What a fascinating build Geoff.

I've seen this type of design a few times before but never on this Continent. I'm looking forward to seeing your firing pics.

Have you decided on what sort of insulation layer you are going to use over the brick dome structure? You look like you are limited for space on the sides of your base structure?......although this is a quick fix with many drill and fix or canter-lever options that can be easily fixed to the support base to support any insulation layers.

Love the design......looking forward to seeing more pics.

Terry

[geoffisegwr]

Hi Terry, thanks for your kind words.

must admit, i have spent some pondering the insulation issue and how to minimise the thickness.

I did came across a build which used a double blanket (2x50mm) approach, which seemed fine, but was concerned about rendering directly on to the blanket.

You mentioned a canter-lever option, is this something you have done ?

cheers

JT

[geoffisegwr]

Here is an update and a couple of photos.

I was able to extend the base plinth on one side, but had to put up some timber supports on the side and the back. As the timber was attached to the concrete block base, i guessed it would far enough away from any heat. 

With regards to the insulation i opted for the thermal blocks and loose vermiculite infill for the lower section of the vault then a double blanket layer over the dome.

The bottom row was a solid block (this brought it up to hearth level), then i cut out shoulder sections for the middle layer. With a few more cut notches, this formed a cavity (50mm) around the lower sections (vertical) of the vault. This was then filled with loose vermiculite (about 1/2 bag). I used some of the cut out pieces (50mm) to continue the side walls up to the top of the dome. To provide some lateral support for the upper layer, i inserted some small pieces of thermal block to provide some into the cavity, then continued to fill with loose vermiculite. 

I used one roll of thermal blanket (50mm) to cover the top of the dome. There was enough left to provide a double layer over the main part of dome.

Fitting the wire mesh was a bit of a faff, but by attaching it to the side walls (thermal block) with some small screws and using a rubber mallett, i was able to get tension and shape right.

I used the standard render mix (4xsand: 1xcement: 1:lime: waterproofer) and it went on quite easy using the hand and trowel method. There didn't seem to be any problem putting it directly over the blanket. But well have to wait to see what it is like after it dries. 

I have got some stuff left over, which I will get round to listing in a bit (2x bags of fire clay, 1x bag hydrated lime & 1/2 bag of vermiculite)

cheers

JT

[cobblerdave]

G'day
Wow that looks great. Going to work well with that insulation too.
Only seen a couple of these ovens over the years but never one complete, so this is a first for me.
They are nice and compact and you've used you limited space well.
Regards Dave

[uldis]

Hi, geoffisegwr. I'm planing to make similar build. Please share your baking experience in this oven. Are you satisfied with it?

[geoffisegwr]

Hi,

So far i'm really pleased with it. i've only cooked for the family so far but have an upcoming pizza party on monday so should be a good test.

Once the oven is up to temperature (definitely recommend kiln dried wood), i push the embers to the side and cook in the middle (see photo). However on my last cook, i pushed the embers to the back and was able to cook 2x pizza side by side.  As i'm still getting used to it, we have been using the metal pizza pans (especially useful when the kids load up on toppings!). Hopefully a slight tweak in the dough mixture and using semolina, i'll graduate over to cooking straight on to the stone. 

With regards to baking, managed to do a ginger cake (before the insulation applied) then a coconut cake night before last. Temperature wise, i got it up ~300 - 350deg in about 90mins with a minimal fire. The oven was still warm the following morning, the dome bricks were registering ~80deg.


if you need any more info, i have put together a material list (and even some plans).

JT

[geoffisegwr]

After a couple of days of dry weather, managed to get some paint on and at last its finished.

Looking forward to an Indian summer to make the most of it. 


I've got some bags of fire clay and hydrated lime (and half a bag of vermiculite) left over and have listed them in 'buy and sell' section. (i'm in cardiff).