Oven floor tiles - appropriate size

[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

[BelgianBuilder]

Ok. Thanks for the advice, David. I will cut a piece out along the perimeter for the insulation to fit in.

Any idea on the positioning of the brick for the inner arc?

[david s]

Extending the floor tiles out beyond the outer perimeter of the inner dome is inviting heat loss via conduction. Generall it is better if the whole dome is encapsulated in insulation.If it were mine I'd be trimming off those floor bricks with a large 230mm angle grinder and diamond blade.

[BelgianBuilder]

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!

[BelgianBuilder]

Thanks you all!

[JRPizza]

Hey BelgianBuilder , I would not want to build an oven without a chimney, but if you do a search for bread ovens of Quebec (link below) you can see examples of rustic ovens and quite a few of them do not have any sort of chimney.

http://heatkit.com/docs/Bread%20Ovens%20of%20Quebec.pdf

[mongota]

Geting a flat floor:

I went through my stack of ~250 firebrick until I found enough of rough equal thickness bricks to use for the floor.

I then laid out the bricks I chose in a herringbone pattern, the pattern I chose for my floor. The pattern was dry set on nothing more than a flat sheet of plywood. I inspected the surface of the floor for irregularities in brick thickness. I moved one over there, tossed one out and replaced it, etc. Only took a few minutes. I ended up with a pretty flat cooking surface.

Once I installed my 4" of rigid CF board insulation on the slab, I transferred my floor bricks from the plywood to the insulation, their final resting place on top of the insulation.

I ended up with a nice flat floor. No leveling or bedding material needed.

After you oven is built, it you find a brick edge that constantly catches the peel, just hit that raised edge with an angle grinder to take it down. A quick swipe will do it.

Best, Mongo

[BelgianBuilder]

Thanks a lot for these useful replies!

I'll go for the thicker but smaller tile to minimize risk of cracking.

I will cover an area somewhat bigger than the dome itself with the floor tiles, for aesthetic and practical reasons (easier to cut straight lines). It seems weird not to apply anything to bed the floor tiles down outside the perimeter of the dome, I suppose I could mortar down the tiles not covered by the dome and level the tiles inside the dome with plain sand?