Home brew oven on an oak base - Warwickshire UK

[david s]

You will find that your oven will continue to improve in performance because it takes quite a number of firings (many more than you'd think) to drive out all the moisture.

[Kris S]

Looking good!

Personally I think 80cm internal diameter is the sweet spot, I chose 70cm and while the floor space is large enough to cook what I want, I could have done with just a little extra space between the fire and pizza.
at 380 - 400°C and so close to the fire, I have to be watchfull and rotate the pizza quickly to not let it burn on the fire side.
It has happened once that the fire tumbled down and on my pizza as well

Being so small the oven is at pizza temp in under 1 hour, big advantage imo. I can imagine yours will not take much longer.

[Matts]

It has been a while since my last update but my oven is finally getting there, we had our first pizzas over the weekend and they were fantastic! I had expected the first to be a burned mess and to for it take a bit of practice before getting any good at cooking pizza, but not at all.


The oven still needs a coat of render, and possibly a roof; I cant see it still looking good and not getting quite damp inside the after a UK winter without some sort of protection.

We are also looking forward to trying different styles of cooking in the oven; at some point I will make a door to fit the reveal left on the inside for some longer bakes. Then there are the worktops that i'll put either side for pizza/bbq prep... A busy summer ahead, but now fuelled by pizza!

[david s]

It’s looking very good. Usually the flue gallery is made a little higher and wider which leaves a rebate so a door can be placed against the oven mouth. Making it lower than the oven mouth might make fitting and sealing a door difficult.

[Matts]

A bit more progress over the last week, I built the arch, and cast the gallery behind.




I tied the arch to the gallery with a few bits of wire between the mortar gaps. I made the arch top slightly lower the the dome entrance and with a decent depth to the gallery hopefully it should collect the smoke nicely. I also kept the contact point between the gallery and dome to a minimum to slow down heat transfer.




I also got the dome covered in a couple of layers of 25mm ceramic blanket, with a third over the top made of the scraps left over from cutting it to shape.




Getting the blanket and the wire to fit wasn’t as easy as I hoped it would be, I ended up using a tool of thicker wire to hold it all in, pushing it in to the ceramic board at each end held it down well.

[Matts]

What size is the oven and the flue in that link?

it looks like a 4” flue but maybe perspective is a bit off.

[david s]

You will need to cast the flue gallery before proceeding to the insulation layers.
You are correct about the courser grades being more difficult to apply. This is also exacerbated if using a leaner mix. Unfortunately the finer the grade the more water that is required for the mix, the excess after hydration needs to be eliminated. Because a range of grain sizes makes a better mix, I compromise and use a medium grade perlite and a fine grade vermiculite mixed 50/50 with 1 part cement to 10 parts of the insulating aggregate and a handful of powdered clay for every litre of cement added. The clay makes the mix more workable
The ingredients I use in the 10:1 mix requires 4.2 parts of water by volume. If you mix the dry ingredients in a barrow and add the water slowly it should just pool at the bottom of the barrow after folding in gently. Do not use a mixer as it abrades and degrades the grains a as well as sticking like crazy to the mixer sides and blades. After a couple of minutes the perlite and vermiculite should have absorbed the excess water. Too much water will just wash the cement off the grains, so be careful.
A 100L bag of each should be plenty, but it depends on how many layers of blanket you apply. Any excess can be used in the garden, great for moisture retention. I use it to add to my compost if it's looking a bit wet. Work out the volume required using 4/3 x pi x r3, and make up batches of around 20L at a time.

Make sure you wear gloves or you’ll regret it.

Here's a link to a gallery and arch repair I did, which details the build of a nice shallow gallery that produces excellent smoke flow and extraction.
Start here
https://community.fornobravo.com/for...723#post435723

[Matts]

With a start made on the dome I am looking forwards to the next stages, I was about to buy the vermiculite/pearliete to layer on top of the ceramic blanket but I have found a few different grades available:

pearlite 1-6mm, 3-8mm
vermiculite 2-6mm, 1-12mm

which grades work best for this part? I guess larger grade will leave more insulating air gaps but may be harder to work with?

Is 100l of each enough to cover the dome and gallery?

[david s]

Not sure how fine your homebrew sand is, but it does help to sieve out any course sand from the mix, which makes it easier to fill fine voids. Mix to a peanut butter consistency and force it as hard as you can into the voids.

Hold the moisture in the casting for at least 7 days. (see accompanying link) to enhance its strength.

https://www.ccaa.com.au/documents/Li...2006Curing.pdf

[Matts]

I checked on the oven this evening, glad I did as it was ready to remove the form and sand but still green enough to blend in the worst of the voids/ripples.

I had not realised quite how much sand and bricks it took to build the sandcastle. I used a 800mm circle of DPM to mark out the base when I built the sand castle, this worked really well to keep the base clean and dry.

There were a few ripples in the casting where it slumped, and voids where it did not quite mould together, a little fresh mix seemed to blend in quite nicely to smooth these out, hopefully once set it will hold.

[david s]

I hope you’re right. Most ovens sit on a 4” thick reinforced concrete slab, which, depending on how much weight it has to support, may be overkill, but remember that the strength of a slab is directly proportional to the square of its thickness. Thus, a 2” thick slab will be 1/4 the strength of a 4” one. That is a full slab, not three lintel blocks. No idea how thick your lintel blocks are, what the span is, or what sits between them and the insulating board, but it looks to me, from just viewing the pic, somewhat on the light side. Reducing the span by cantilevering or adding additional piers under the centre might be prudent.

[Matts]

There are six joist hangers for 4x8 joists, each is rated for a few hundered kg static plus dynamic loading you get with floors. The oven will be 4-500kg at best so won’t trouble the base.

[david s]

Nice job. Don't worry about the newspaper, it's only purpose is to provide a nice smooth surface on the inside and to stop the castable from picking up sand. just give it a really good scrub with a stiff scrubbing brush to avoid dropping sand on your pizza. The newspaper, if any remains stuck in the castable, will just burn away. Wait at least two days before removing the front plate and the sand before filling any of the voids on the inner surface. Holding moisture into the casting for at least a week will enhance its strength so once the voids on the inner surface have been filled cover it with wet hessian or similar and seal it all up.

Not sure how big your oven is, but it will be heavier than you think. If those galvanised truss ties are all that are holding the weight of the oven, you should have a couple of decent props in the centre of the stand to support the oven's weight.

[Matts]

I got the dome cast today, the sand castle was easy to build, very neat with a shaped form to keep an even profile all the way around.

Not sure if the newspaper was worth the hassle, hard to get on, kept drying out and blowing off, then was moving around as I put the homebrew on.

I mixed the homebrew as dry as I dared, it went on by hand nicely, a little slumping but nothing significant, then I floated it smooth and finished with a wooden float to keep the finished surface a bit more open to vapour.

Now it’s all wrapped up with a few blankets as it looks like being frosty tonight.

I will see how form it looks tomorrow and maybe start removing the form and sand.

[Chach]

If it falls under the building code it is illegal in most places to have a single wall penetrating a ceiling or roof.

100% agree!