32" build in Calgary, AB - pompeii neapolitan

[david s]

Because moisture always travels away from the heat source and gravity also assists in it accumulating under the floor bricks, the insulation layer, which is highly hygroscopic (unless you choose foam glass), the underfloor insulation layer has the ability to hold a very large amount of moisture (check the volume of your proposed underfloor insulation. Unless trapped moisture is given a pathway exit, complete drying can take months. Remember that one litre of water creates more than 1500 litres of steam. So in addition for this steam to escape the holes also act as pressure relief. The large amount of water added during the build needs to be teased out slowly. In addition, if weather is allowed entry to a dry oven it also accumulates in both the dome and underfloor insulation layers. Depending on climate, apart from rain, humidity also accumulates in the whole oven, even if covered by a roof. This alone can impact the oven’s performance and often a long slow fire the day before a decent cook up is a good idea if the oven has been idle for some time.

[UtahBeehiver]

As David mentioned, we do not see builder normally plan and research there build like this, so kudos to you. A couple comments. Both the inner and outer arch dimensions don't seem to account for the mortar gap so dimensions may need to be adjusted. On the inner arch, consider a taper inner arch to make to dome to inner arch interface more seamless. Takes work to do this arch but pays off on the back end when mating the dome to the arch. With a tapered inner arch you need to start with a full length brick so 4.5 length bricks will not work. There are many examples out there. JR Pizza did a good job on this. Here is an example of a tapered inner arch from my build. Taper Arch Example.pdf
Also, you can attached up to five pics on a post if you keep the pics below 1.25 meg (know this is small by todays standard) .

[UtahBeehiver]

Why don't you set up a thread in "Pompeii Oven Construction" and I will move all the posts to that thread. This topic/area is the one that gets the most activity and views.

[IH123]

Because moisture always travels away from the heat source and gravity also assists in it accumulating under the floor bricks, the insulation layer, which is highly hygroscopic (unless you choose foam glass), the underfloor insulation layer has the ability to hold a very large amount of moisture (check the volume of your proposed underfloor insulation. Unless trapped moisture is given a pathway exit, complete drying can take months. Remember that one litre of water creates more than 1500 litres of steam. So in addition for this steam to escape the holes also act as pressure relief. The large amount of water added during the build needs to be teased out slowly. In addition, if weather is allowed entry to a dry oven it also accumulates in both the dome and underfloor insulation layers. Depending on climate, apart from rain, humidity also accumulates in the whole oven, even if covered by a roof. This alone can impact the oven’s performance and often a long slow fire the day before a decent cook up is a good idea if the oven has been idle for some time.

so under a linear force like gravity or increasing force like heat pressure from dome, the moisture will be pushed downward from hearth->insulation-> perlte-cement->concrete slab, however the water is going to likely be moved over the entire oven footprint and even radiating outwards on the concrete slab; creating a weeping holes in the slab will accelerate the penetration in a 5.5" thick slab however that only applies for the following: direct area under the holes and on top surface (which is relatively going to be very small compared to oven foot print), and, as moisture reduces near the holes then more will be absorbed towards it creating like a micro stream to the holes; however, there is still the heat and gravity and I am not sure how much faster a tiny hole with small surface area will shed. my original plan for this is was: as the water reaches the top of the concrete slab, it could escape outwards if there is any type of moisture barrier (like aluminum foil or vapour barrier on slab) and seep sideways all over the insulation edges. if you see my perlite-cement insulation diagram, I would have to leave the entire edges of the insulation (side edges) fully exposed so moisture can leak through outwards. it might be a larger area than few holes. I am sure having many tiny holes on the slab will help however on the expense of the rigidity and structural strength of the slab. moreover, most of my oven foot print (dome walls and hearth) are over cmu cores that are fully grouted so any moisture will travel into those grouted cores and saturate them downwards to the bottom slab, very little is left for streams to flow into holes.I am thinking if I could just not create any holes on the concrete slab, the perlie-cement layer is a sponge and would seep any liquid moisture from sideways. if the sides of the oven (roof/siding) are water proof then no water moisture would come in direct contact. what do you think?

[IH123]

As David mentioned, we do not see builder normally plan and research there build like this, so kudos to you. A couple comments. Both the inner and outer arch dimensions don't seem to account for the mortar gap so dimensions may need to be adjusted. On the inner arch, consider a taper inner arch to make to dome to inner arch interface more seamless. Takes work to do this arch but pays off on the back end when mating the dome to the arch. With a tapered inner arch you need to start with a full length brick so 4.5 length bricks will not work. There are many examples out there. JR Pizza did a good job on this. Here is an example of a tapered inner arch from my build. [ATTACH]n471130[/ATTACH]
Also, you can attached up to five pics on a post if you keep the pics below 1.25 meg (know this is small by todays standard) .

Thank you, my design diagrams fell short of the actual. I saw many videos and have idea of the shape. I will try to keep the block near the inner arch a full brick. as for the mortar gap, each time I cut the width will be less than an exact half because of the blade thickness. moreover, I plan to cut larger and trim later as cutting shorter is irreversible.

[IH123]

Why don't you set up a thread in "Pompeii Oven Construction" and I will move all the posts to that thread. This topic/area is the one that gets the most activity and views.

I did: https://community.fornobravo.com/for...eii-neapolitan

Thanks for taking care of the moving

[david s]

Thank you, my design diagrams fell short of the actual. I saw many videos and have idea of the shape. I will try to keep the block near the inner arch a full brick. as for the mortar gap, each time I cut the width will be less than an exact half because of the blade thickness. moreover, I plan to cut larger and trim later as cutting shorter is irreversible.

This method of cutting the bricks (depending on their actual size) may be helpful in reducing the number of cuts (3 cuts gives you two bricks), with minimal wastage. The wedges can also be used to fill gaps from the outside.

[IH123]

Today's progress: completed the centre work-form (the one that will never be removed after pouring the slab), and partially the first perimeter work-form. next is the outer most perimeter work-form.

[IH123]

This method of cutting the bricks (depending on their actual size) may be helpful in reducing the number of cuts (3 cuts gives you two bricks), with minimal wastage. The wedges can also be used to fill gaps from the outside.

Thanks, I've seen this on the forums and might use it. however, it could cost another wood jig for the wet saw to cut it, I might just cut half all of them and then make jigs for each course (I might need 2-4 jigs per each course however I would once finish fully a course re-use the same jigs and make the angle cut less). my wet saw has nothing to mitre except the 90 degree tray and I will be making the custom mitre jigs . I chose to have the entire dome be derived from same cut (taper and wedge) however as courses go up there is another two cuts on it to fit it in the sphere ( so not really all jigs need to be constantly changed per course)

[david s]

No don’t cut them in half first. You will waste cutting time, blades and create double the amount of offcuts. As each chain rises so the angle becomes greater. If you can’t use a jig just mark out the brick with a template and cut to the marked line without a jig. It’s not hard.

[david s]

If you are still planning on pouring your own vermicrete slab, be aware that because of the hygroscopic nature of the grains there is far more water required in the mix that needs to be removed. Check my experiment on drying a vermicrete slab, attached. Using calcium silicate board, although far more expensive, has the advantage of already being dry, so there's far less problem about removing underfloor moisture. The underfloor weep holes in the supporting slab greatly assist in this water removal, particularly for the initial drying fires after the build is complete.
Vermicrete insulating slab PDF.pdf

You will also need the vermicrete table. As the table shows a higher proportion of cement provides strength but reduces insulation value. So, use a 5:1 mix for underfloor to provide sufficient strength for the floor bricks and oven. You can go far leaner for over the dome insulation (I use 10:1 over the blanket layers), but if you are still doing the enclosure style just using loose perlite or vermiculite is a better cheaper and simpler insulation solution than a blanket and vermiculite combination.

[IH123]

today's progress:installed more of the work-form, still need to fill gaps, secure work-form for slab load , and test rigidity.