Oven floor tiles - appropriate size

[david s]

Of course.I don’t because I prefer the faster setting proprietary castable refractory for that application. If you use homebrew remember to add some burnout fibres.

[BelgianBuilder]

Thanks david s ! That is clear. Can I use the same homebrew recipe for the dense castable surrounding the sleeve as I 'd use for the gallery?

[david s]

. Doesn't every oven in a colder climate need this for hibernation? Just a a bit confused about this sentence:

"I surround the sleeve with some dense castable about 100m highto cover them the sleeve not being a full circle allows for it to have some expansion relief."

-> From other pictures, I assumed you didn't integrate the 'collar ' in the cast, but that you fixated it in the vermicrete/render applied higher up. Are you talking about a different 'castable' than the cast gallery? [/QUOTE]

You need a much bigger gap than 0.8mm. I use around 8mm and the double layer of corrugated cardboard in pic2 is what I use to form this gap.
Pic 1 shows how I form the sleeve (be aware that the sleeve at this point is upside down. It also shows how the sleeve does not make a full circle. This allows for it to expand without placing stress on the casting that surrounds it as well as accomodating the lapped joint of the pipe which slides into it.
Pic 2 shows the three tabs which prevent the sleeve from sliding too far into the casting and the triangular bits bent slightly outward to give positive bonding to the dense castable that surrounds the sleeve around 100mm high. Higher up, to the top of the sleeve, the sleeve, it is surounded with 5:1 vermicrete.
Pic 3 shows how these materials are contained around the sleeve. I use a layer of aluminium insect screen surrounded by bird wire for this.

Because we live in the tropics we only ever see the temperature drop down to 10C (50F) about three times during winter so have no need for "winter hybernation", However, I've done lots of these for either mobile ovens or if transporting a finished oven where the flue pipe is difficult to package and its seating is vulnerable to damage.

[BelgianBuilder]

Thanks a lot again!

The homebrew castable seems the way to go. If vermiculite + plaster is easier to remove than vermiculite + cement, I'll do that. Bit worried already about removing the mould plug without damaging the cast. david s is it the same product as used for pottery or is it something else?

Toiletman Nice work on insulating your oven! Were you planning on applying the vermicrete layer before the curing fires? Won't the vermicrete impede moisture loss?

Btw you mention cross sectional area, but give a measurement of single dimension. Do you mean the depth instead?

I meant depth indeed. As david s suggested, I am going to leave a gap of 0.8mm between the cast and the outer arch, so effectively there won't be any pressure on the outer arch.

david s such a simple but ingenious design to create a removable flue. Doesn't every oven in a colder climate need this for hibernation? Just a a bit confused about this sentence:

"I surround the sleeve with some dense castable about 100m highto cover them the sleeve not being a full circle allows for it to have some expansion relief."

-> From other pictures, I assumed you didn't integrate the 'collar ' in the cast, but that you fixated it in the vermicrete/render applied higher up. Are you talking about a different 'castable' than the cast gallery?

[david s]

A belated thanks Toiletman and daidensacha for the advice.

Both your builds are intimidatingly well executed and demonstrate a level of craftmanship I can only dream of as an office clerk making something real for once.
Anyway, diversity in looks is a good thing I suppose, also when it comes to pizza oven.

Following your guidance, I am convinced casting the gallery is the way to go for me, as my entry is quite narrow (only 8.3 inches) and actually it seems less complicated then a brick vent gallery.

1. From the various methods I have encountered on the forum, I do wonder which one is easiest or what other pro's and con's I should consider?

- making a mould plug out of sand or vermicrete or vermiculite and casting plaster and apply the refractory castable by hand?

eg. https://community.fornobravo.com/for...rch#post435723

- make a formwork from wood/polysterene that you can fill with your refractory castable?

eg. https://community.fornobravo.com/for...eapolis/page14

2. If cross-sectional area of the flue were to be 5,9 inches, it would leave only 2.3 inches (brick width) for the outer decorative arch. Is that a problem?

3. Use of tie wires in the brick joints to connect outer arch to the gallery: do you connect them to the refractory castable or to the outside render?

4.If you can find refractory castable, why would you consider making a homebrew? Because it is cheaper? Refractory castable costs around 65 dollar a bag (25kg) around here. Difficult to assess whether one bag would be sufficient. I guess if you stick to a minimum thickness of 2 inches, it should be.

Toiletman : 5. In your thread, someone commented on the angle for the smoke to make it into the gallery. I never considered that, I thought this was sort of covered by the basic design.
What exactly are the reference points for this angle and how do you account for that?

6. Lastly, on the chimney, I don't think I will use an anchor plate. The system of a removable flue shown in Toiletman thread seems very clever. As it allows for space for contracting/expanding, I suppose a single walled flue is sufficient? Any advice on things to consider when buying the chimney system?

Thanks a lot. Couldn't do this without help from this forum!

1. Casting is far easier and allows compound curves, whereas with brick units you are stuck with the thickness of the brick and also creating mortar joints where failures are more likely to occur. Using a castable also allows a far thinner casting reducing weight and the heat sink effect which saps the dome of heat.The thinner thickness resulting in reduced strength can be compensated for by the addition of reinforcing fibres.
3. I make a thin (lightweight gallery casting with an 8mm gap between it and the outer decorative arch which allows the expansion floor, dome and gallery inside the cooler outer shell and decorative arch. This therefore requires a good bond between the the outer shell and the decorative arch which become well integrated with with wire ties.Other builders have isolated the gallery from the dome to achieve a similar outcome.
4.Not only is castable refractory expensive, but it’s tricky to work with if you’ve had no experience with it. It contains high temperature aggregates capable of withstanding more than double the temperature an oven would see. Its full strength is only achieved when fired to a temperature which vitrified the material. This is not possible to be done in situ with wood and is almost certainly likely to result in failure. The partial strength achieved by the chemical bond if unvitrified is adequate however and extended damp curing is not required as is for a homebrew casting.
5. The funnel form allows for a smooth flow of smoke to the base of the chimney, just as the replacement of an ICE manifold with headers improves the engine to breathe more efficiently.
6. Anchor plates as used by most builds are expensive and take up quite a bit of realestate where the pipe joins it. If the oven is outdoors and it does not penetrate a roof, a single pipe is perfectly adequate. Hot to touch but well out of the way of small children. The double flue adds further labour and expense not required for most builds.

[Toiletman]

A belated thanks Toiletman and daidensacha for the advice.

Both your builds are intimidatingly well executed and demonstrate a level of craftmanship I can only dream of as an office clerk making something real for once.
Anyway, diversity in looks is a good thing I suppose, also when it comes to pizza oven.

Thanks, and very happy to help. This whole build was also the first time touching mortar and bricks for me. You must also experience that you are getting better with each row right? daidensacha is in a league of his own with respect to the finish and exceptional use of materials.

It's wonderful that we can all learn from each other by documenting our builds and exchanging expertise.

Following your guidance, I am convinced casting the gallery is the way to go for me, as my entry is quite narrow (only 8.3 inches) and actually it seems less complicated then a brick vent gallery.

1. From the various methods I have encountered on the forum, I do wonder which one is easiest or what other pro's and con's I should consider?

- making a mould plug out of sand or vermicrete or vermiculite and casting plaster and apply the refractory castable by hand?

eg. https://community.fornobravo.com/for...rch#post435723

- make a formwork from wood/polysterene that you can fill with your refractory castable?

eg. https://community.fornobravo.com/for...eapolis/page14

For me the applying by hand worked out pretty ok in the end. My biggest mistake was mixing the castable too wet which made it sag, but in the end this was all repairable. It was good to have some areas of support around as well. The main reason for me to go the 'apply castable by hand method' was that I was not looking forward to the complexity of the mold I would otherwise have to make due to the complex shape of the chimney. If you can make your chimney shape such that you can deal with a more simple mold you might consider otherwise. I also used vermicrete as a mold, making vermiculite plaster would make removing it a whole lot easier.

2. If cross-sectional area of the flue were to be 5,9 inches, it would leave only 2.3 inches (brick width) for the outer decorative arch. Is that a problem?

I've seen people use brick veneer for the decorative arch, so I don't think that's a problem. Of course I'm assuming the strength for supporting your cast comes from the cast itself, and not from the decorative arch? The front part of my arch is also roughly half a brick deep and so far is holding up fine.
Btw you mention cross sectional area, but give a measurement of single dimension. Do you mean the depth instead?

3. Use of tie wires in the brick joints to connect outer arch to the gallery: do you connect them to the refractory castable or to the outside render?

I considered this, but did not see anyone else using or recommending them, so my gallery is freestanding. Just having an airgap fitted with seals (ie. firerope 'kachelkoord' and fireproof kit (I went with the 'permatex ultra copper' based on david s 'advice.

4.If you can find refractory castable, why would you consider making a homebrew? Because it is cheaper? Refractory castable costs around 65 dollar a bag (25kg) around here. Difficult to assess whether one bag would be sufficient. I guess if you stick to a minimum thickness of 2 inches, it should be.

First reason: I have plenty of the ingredients left over after finishing the dome. Second reason: I've heard people mention that the refractory castable goes off really fast, so that felt risky for me, using this method and a mold for the first time. Third reason: afaik you really have to 'pour' the refractory castable, where the homebrew you can apply by hand without needing a complex mold.

Toiletman : 5. In your thread, someone commented on the angle for the smoke to make it into the gallery. I never considered that, I thought this was sort of covered by the basic design.
What exactly are the reference points for this angle and how do you account for that?

What I've seen from fireplace/stove (kachel/haard) sellers is the recommendation to always keep any chimney pipes going upwards at a 45 degree angle, so that's what I tried to model. You might also ensure the smoke first has some mainly 'vertical' path from the oven mouth upwards, such that it gets some upwards momentum, before you are trying to gently 'squeeze' it into the chimney pipe.
On the gently squeeze you can find quite some literature on aerodynamics, especially considering flow separation in diffusers. These typically give guidelines on a total angle of maximum 12-14 degrees or something. But that's 'expanding' the air, while we are trying to 'squeeze it'. In general that's much more forgiving, as the air gains speed/energy while being squeezed. However, in general it's a good idea to try to make the 'squeezing' section as high as feasible for your build.

6. Lastly, on the chimney, I don't think I will use an anchor plate. The system of a removable flue shown in Toiletman thread seems very clever. As it allows for space for contracting/expanding, I suppose a single walled flue is sufficient? Any advice on things to consider when buying the chimney system?

That design was actually provided by david s in my thread. He posted some great pictures explaining it, as well as links to other posts where he details it more. It seems the result of years of his experience in optimizing the pizza-oven design.
The choice of single vs double walled is mainly about safety afaik. Safety for people touching it (?) but especially safety for combustible materials around the chimney. I've also heard people complain about the heat radiating from their chimneys, I'm not sure if that's a thing for the gallery, or also for the chimney pipe?
I went for double walled:

• thinking that people might be able to touch the chimney (I think it now ends up that high that that's not really feasible)
• planning on building a gazebo/pergola kind of constructing with climbing plants above my pizza oven, which I wouldn't want to burn with the heat radiating of a single walled pipe.

Thanks a lot. Couldn't do this without help from this forum!

Couldn't agree more!

[BelgianBuilder]

A belated thanks Toiletman and daidensacha for the advice.

Both your builds are intimidatingly well executed and demonstrate a level of craftmanship I can only dream of as an office clerk making something real for once.
Anyway, diversity in looks is a good thing I suppose, also when it comes to pizza oven.

Following your guidance, I am convinced casting the gallery is the way to go for me, as my entry is quite narrow (only 8.3 inches) and actually it seems less complicated then a brick vent gallery.

1. From the various methods I have encountered on the forum, I do wonder which one is easiest or what other pro's and con's I should consider?

- making a mould plug out of sand or vermicrete or vermiculite and casting plaster and apply the refractory castable by hand?

eg. https://community.fornobravo.com/for...rch#post435723

- make a formwork from wood/polysterene that you can fill with your refractory castable?

eg. https://community.fornobravo.com/for...eapolis/page14

2. If cross-sectional area of the flue were to be 5,9 inches, it would leave only 2.3 inches (brick width) for the outer decorative arch. Is that a problem?

3. Use of tie wires in the brick joints to connect outer arch to the gallery: do you connect them to the refractory castable or to the outside render?

4.If you can find refractory castable, why would you consider making a homebrew? Because it is cheaper? Refractory castable costs around 65 dollar a bag (25kg) around here. Difficult to assess whether one bag would be sufficient. I guess if you stick to a minimum thickness of 2 inches, it should be.

Toiletman : 5. In your thread, someone commented on the angle for the smoke to make it into the gallery. I never considered that, I thought this was sort of covered by the basic design.
What exactly are the reference points for this angle and how do you account for that?

6. Lastly, on the chimney, I don't think I will use an anchor plate. The system of a removable flue shown in Toiletman thread seems very clever. As it allows for space for contracting/expanding, I suppose a single walled flue is sufficient? Any advice on things to consider when buying the chimney system?

Thanks a lot. Couldn't do this without help from this forum!

[daidensacha]

Hi, I had similar questions about what sizes of the vermiculite and perlite to buy in Germany for my insulation. david s has a lot of experience with it and was really helpful.

V-P-crete
Here is what I used for my v-p-crete insulation mix over my dome. Note I also used ceramic fibre blanket over the dome before adding the v-p-crete but my goal was to retain heat for days to use the oven to cook other things the days after cooking pizza.

• 5 parts vermiculite (2-3mm)
• 5 parts perlite (2-6mm)
• 1 part portland cement
• 4 parts water (added 1/3 at a time and hand mixed in bucket or barrow) (in the end this was not fixed and I added water until it felt right by touch)
• 1 (generous) handful of clay powder per litre of cement added

You don‘t have to add clay powder but its not expensive, and i found it helped when pressing the wet v-p-crete over the dome, with the sticky factor to hold it together. I basically put handfuls at a time in rows, placing and pressing the handfuls in place before adding the next.

Arch vent
Over the arch I considered cutting and cementing bricks (I used schamotte) over the arch to build up a flat platform on which to mound my custom pre-cast vent. In the end I simply cut some formwork to sit on the arch flush with the top, and then filled it with refractory concrete. It was a quick and easy solution, done in a couple of hours. I documented with images in my oven thread, its very simple.

Casting the vent, if you want to do that is a process that takes a bit longer, with several steps. I did it so I could create a smooth transition from the rectangle vent in the arch to the inner 200mm diameter of the flue. The goal was to have a clear path for the smoke. I have to say it works like a charm, is like a vacuum and sucks 100% of the smoke directly up the chimney flue. While I cast my vent separately, ( before i even started on the oven), there’s no reason you couldn‘t apply the same technique to cast one directly in place on the arch. Simple need to make a form from 5:1 or 7:1 vermicrete, that would be the shape (make a block, then carve it back to the shape you want your vent to be) of your inner vent (this is scraped out after casting the refractory concrete around it). Then make up some formwork around the form, leaving space between it and the form to ensure you get a thick enough vent wall. Fill it with the refractory concrete, and wallah. When the concrete is set, scrape out the vermicrete and you have a vent gallery.

My alternative before deciding to cast my own vent was to brick it up, cutting the inside of the bricks that would be the inside of the vent gallery. I have no experience doing it this way.

I documented with lots of photos throughout the process of making my oven, if your looking for ideas, or something more visual so you can work out what works best for you.

[Toiletman]

Hi everyone!
It's with sadness that I have to admit I let my favorite project unattended for such a long time. I think we all know the feeling just not getting to do the thing we'd like to do the most.

Same here: other obligations and winter weather has paused my build as well. Planning to do some indoor molding work during the Xmas holiday.

Anyway, next weekend we plan to finish the brickwork (of the dome). I have a few questions before winter kicks in.

- I assume it is a good idea to cover the dome immediately with the insulation blanket and then put a waterproof canvas over it, even when damp curing has yet to be completed? Would that help prevent the frost reaching the brickwork in the event it would freeze?

Not sure if this response is still in time, but for what it's worth: I've left mine without the insulation and under a tarp. But for me the mortarwork was done well before it started freezing at night. If you still have wet masonry it might indeed be good to insulate it and possibly provide a heat source inside of the oven as well (ie. builders lamp). Make sure to test that it doesn't get a risk of fire ofc. I'm not sure if you would like to use the high temperature blankets, or just any kind of insulation material, as you might not want your final insulation to soak up any excess moisture in case of small leaks.

- For the perlite/vermiculite render: what do I use best, perlite or vermiculite? I can choose between different sizes of grains (1,5 mm (0,6inch) ; 3mm (0,11 inch); 5mm (0,20 inch)). Whats conventional wisdom here and is it a good idea to add hydrated lime to the mix?

Afaik you can exchange perlite for vermiculite 1:1 on volume basis. Afaik the current best ratio's are 10:1 vermiculite to cement for insulating concrete, mixing in water until 'the right consistency'. Traditionally it was 5:1 I think. In that 10:1 as mentioned you can exchange perlite for vermiculite as wanted. I'm planning on going 5:5:1 vermiculiteerlite:cement. I went with the 0-3mm vermiculite.
I'm sure there's more people that will add their €0,02.

- Toiletman Thanks for the lead to kachelmaterialenshop, they have a lot on offer! My oven is 34 inches, so for a flue I was considering a 150mm diameter and 1000mm length. But how do I connect the flue to the brick vent? This most resembles the anchor plate I view in different threads, is this the thing I need?

- Building the vent will be for another time, but I am wondering if anyone can link to a thread with a clear explanation of the design? It seems complicated since the arch is curved and you need to build a level base. Probably this is a newby question since no one seems to have any problems with it.

Have a look at my build thread. David A s provided some very helpful comments on how to build the vent connection yourself. I posted some sketches of how I understood his design and that's the way I'll go. There's also some idea's on how to connect to the gallery. daidensacha also did a very nice job with his design. basically casting two parts to first make the curved area flat, and then put the square to round connection on top of it.

[BelgianBuilder]

Hi everyone!

It's with sadness that I have to admit I let my favorite project unattended for such a long time. I think we all know the feeling just not getting to do the thing we'd like to do the most.

Anyway, next weekend we plan to finish the brickwork (of the dome). I have a few questions before winter kicks in.

- I assume it is a good idea to cover the dome immediately with the insulation blanket and then put a waterproof canvas over it, even when damp curing has yet to be completed? Would that help prevent the frost reaching the brickwork in the event it would freeze?

- For the perlite/vermiculite render: what do I use best, perlite or vermiculite? I can choose between different sizes of grains (1,5 mm (0,6inch) ; 3mm (0,11 inch); 5mm (0,20 inch)). Whats conventional wisdom here and is it a good idea to add hydrated lime to the mix?

- Toiletman Thanks for the lead to kachelmaterialenshop, they have a lot on offer! My oven is 34 inches, so for a flue I was considering a 150mm diameter and 1000mm length. But how do I connect the flue to the brick vent? This most resembles the anchor plate I view in different threads, is this the thing I need?

- Building the vent will be for another time, but I am wondering if anyone can link to a thread with a clear explanation of the design? It seems complicated since the arch is curved and you need to build a level base. Probably this is a newby question since no one seems to have any problems with it.

Thanks a lot for responding!

[Toiletman]

Toiletman Wow nice build! Impressive tapering! Did you get your other stuff (blanket, perlite) also from the kachelmaterialenshop? Indeed, I went with the mortar. As for the beer, the location of the oven is not that far from the brewery but It 's quite far from where I live. I like all trappist beers (the Dutch ones included ) but if there is one that stands out, it is Orval!

Thx! Indeed, I also got the other materials from them in one order (fireblanket, fireclay, vermiculite, perlite, chimney, calciumsilicate and 'kachelkoord'). Only the stones came from broodoven and sand and cement and such from hornbach. Perlite and Vermiculite might be slightly cheaper from agricultural suppliers, but I didn't find any nearby, and with the shipping costs it made more sense to order everything at one place.

Fully agree on the beers

[nlinva]

I also puzzled about whether it makes sense to take into account the horizontal courses that abut the inner arch in cutting the arch bricks.

In the end I decided against it, feeling that 1) It should be a relatively straightforward cut to adjust the abutting horizontal brick to the arch (as opposed to vice versa), and 2) for structural strength, it is probably best to keep the arch bricks as straightforward as possible (i.e. the way it is explained in mongo's build).

[BelgianBuilder]

NewEnglandNewb Thanks a lot. It's cristal clear now how to figure out the inner and outer diameter. It remains a question whether one should take into account the heigth of the ring intersecting the inner arch, I guess it's not that important.

Toiletman Wow nice build! Impressive tapering! Did you get your other stuff (blanket, perlite) also from the kachelmaterialenshop? Indeed, I went with the mortar. As for the beer, the location of the oven is not that far from the brewery but It 's quite far from where I live. I like all trappist beers (the Dutch ones included ) but if there is one that stands out, it is Orval!

[Toiletman]

Hi everyone!

Slow but steady, we're making progress here.

With a lot of help from this forum, we've made it thus far, but the inner arch is looming large at this point.

I sort of understand the basics of it, but there's one thing that confuses me.

On the full bricks forming the innner arch, you should have two cut lines. One cut line is determined by the inner diameter of the oven. But what determines the second cut line?

Option 1: second cut line is determined by the (estimated) heighth of the ring at which the course intersecting the arch sits. In our design, that creates a lip, so the TDC doesn't make full contact with the brick sitting on top. (see image nr. 1)

Option 2: second cut line is determined by de outer diameter of the dome (or the depth of the brick, in my case 4,13 inches). In that case the brick sits a little bit lower, thus creating a dip in the ring that probably has to be corrected for by shaving off a piece of brick before continuing the next course. (see image nr. 2)

What option is advisable from a construction standpoint? Or is it not that important and is either option fine?

Thanks a lot!

Good choice of beer :-D. Picked up a few cartons and the glass as well last time we visited the brewery/monastery. Do you live close to it?

You mentioned before that you couldn't find fireclay: I bought it from kachelmaterialenshop. Their shipping cost to Belgium and the Netherlands are pretty similar it seems. I might also have some left over once I'm done building the chimney (I live in Eindhoven), although it seems that in the end you went with a refractory mortar?

The arch bricks are indeed a little strange: in the end you'll always end up puzzling the rings going above it into place by shaving pieces off. There's also some pictures on how I did it in my build thread, post #24. In picture nr3 you see an IT additional tool that points out the external diameter of the dome. As everything else I've taken that IT additional tool design from one of the other threads, but I don't remember whose.

For the construction or the visual appeal I don't think anything really matters: it's all compressive loads and invisible.

[NewEnglandNewb]

The best explanation of inner arch to dome transition I have seen is on page 4 of Mongo’s build.

https://community.fornobravo.com/for...ct-build/page4