32" build in Calgary, AB - pompeii neapolitan

[IH123]

I had a 10ftx10ft gazebo put over the site, also cut the ceramic fibre board and CaSi boards and put them in final location. the ceramic fibre board had aluminum foil wrap put on top of it and HVAC aluminum tape on the sides, sides are picked by a needle to let any steam escape from sides (top stays sealed to prevent ceramic fibre going into hearth and cooking chamber ). I noticed the CaSi board cuts are not so difficult to dislodge from their position so I am wondering if a 1/8"-1/4" layer of refractory mortar over the CaSi top (sides kept bare) layed and let cure before any bricks put on it, will keep the boards together while constructing the bricks:

[david s]

As posted previously a wet mortar applied over a very hygroscopic material, particularly if the layer is thin, is nigh on impossible because the moisture will be immediately sucked out of the mortar. Apart from the difficulty in obtaining a flat surface the moisture required for the hydration process will be reduced perhaps to a level which will impair strength. Most builders use a dry mix of fine sand and powdered clay. This acts as a levelling medium because there will be small variations in the thickness of the floor bricks. The dry mix also allows for free movement of individual floor bricks as they receive differing rates of thermal expansion depending on their location.

Try your proposed method by all means, but I think you will have trouble.

[IH123]

I can't get CaSi glue where I live, they don't sell it, I also posted previously that I would create a slurry (much water added to mixed refractory mortar portion) and use sponge to brush the CaSi board with it, this will let the board absorb but also dry the slurry leaving those mortar little droplets waiting to bond to thicker full mortar (not diluted). as this is not structural, its just to have the following outcomes:
1) create a rigidized 1/8" surface over board to reduce or prevent dust leaking out
2) provide a little gluing of the boards together , just to have strength not to easily slip over aluminum sheet below it

I could test on scrap Casi board cuts I have and see if mortar actual bonds and cures strong

once first dome course is constructed and banded using the stainless steel banding, and with its weight, I wont worry about the boards moving under the bricks.

I will use Band Clamp to hold the CaSi board cuts together until I finish the 1/8" coat and the dome's first course. regardless if the 1/8" refractory mortar becomes hard strong or not, as its going to be under play sand , if it dries and crumbles then let be, it would just be another filter of the insulation board dust

[IH123]

I finished today casting a thin 1/8" skim coat over the CaSi board and went smoothly: I had to wet the board with a refractory mortar slurry and then paste the refractory mortar with the wedge of rectangular trowel at about 15 degrees pressing firmly (if not pressing firmly they will like come off however magic happens when pressing firmly, they get like suction gluing to the board - like a car auto body prep), I did the top and then sides, not covering it or wetting it as soon as it cures in 24-48 hours I will build my oven on it. I used Thermobond 915, about 6kg for the top and about 1-1.5kg for sides mixed with 16% water ratio by weight, here are the pictures:

[david s]

That looks pretty good, well done. Because of the large amount of water applied it is advisable to allow sun and wind dry it out as much as possible before locking it in with the floor brick layer. Try and find something else to do for a couple of weeks.

[IH123]

Indeed, needs to dry however it will take me days-weeks to lay the dome spring line and hearth bricks, which will be laid dry except the wet from cutting and head joints:
1) I need to smooth and re-level , at least for dome bricks foot print as the dome bricks will not have levelling play sand or mortar under them.

This is not correct, I am changing this below:
(there will be parchment paper as a slip layer) but that can't level or added in layers as when it burns it could compress or dislocate.
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I do not want gases to escape from cooking chamber from under bricks into insulation render of dome, this will create an exchange of ceramic fibre dust and also leak heat . I will instead pad the dome bricks with very un-wet dry but little damp and VERY THIN refractory mortar such that its packed under the brick creating a tight seal, however it can't bond to the insulation coat properly that when dome expands if any cracks to happen they will occur on that not on insulationcoat
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will use my laser level and grinding to level smooth(might use silicon carbide rub brick instead of angle grinder which could eat too much)
2) vacuum all dust and debris
3) set my wet saw, create cutting jigs (guards, mitres ,clamps,..etc)
4) cut the bricks to shape for dome and hearth
5) dry fit the bricks


so all of the above will take lots of time (I work on it couple hours on some days of week so will be slow.

here are the pictures from today (less than 12 hours from casting), no cracks or issues except lot of smoothing and levelling needed:

[david s]

Here's a method of cutting the bricks which reduces the number of cuts required, But remember that the angle gets grater for each subsequent row of bricks and the doe rises, which requires a jig adjustment. so don't cut more than one row at a time. The wedge offcuts can be used to poke in the gap created from the outside of each row.

[IH123]

Here's a method of cutting the bricks which reduces the number of cuts required, But remember that the angle gets grater for each subsequent row of bricks and the doe rises, which requires a jig adjustment. so don't cut more than one row at a time. The wedge offcuts can be used to poke in the gap created from the outside of each row.

this wont work in my case, my requirement for precise cut requires outer and inner surface to be perpendicular to centre line to provide the most close sphere inner shape as possible, using the method you described, while saves two cuts, would require trimming the inner side edge and outer edge which cancels the saved cuts. moreover, there will be mass inside and outside of dome that are useless heat sucking mass and not part of dome support (outside spiked edges) or dome reflective volume (inside spiked edges). if any to save cuts in my case then would be: (I copied your picture to show you how it could work in my case - modified it:



for the simplicity of my jigs, I will avoid this all over, I am happy to pay for anther blade. I will cut the bricks to half and then trim them. I rather spend more time having a sturdy tested jig that works than trying shortcut jigs that lead to inaccuracy. in my design the entire dome stones will have the same exact cuts 4 times (2 wedge, 2 taper, brick cut to half) after that each course will have 2 to 4 more cuts to fit the curve (polyhedron) therefore saving a cut when each half brick will undergo close to 8 cuts is not something I could use for my design. I would have used it if I was making an approximate however my plan has been to produce the most tight dry fit (almost no mortar) dome and so will focus on my jigs.

[david s]

Ok, but be aware that it will mean many more cuts which leads to more bricks required (expense), more wastage, more blades and considerably more labour. The primary reason for any mortar courses is to create adjustments for slight brick size variations, level and accumulated errors, all of which mean slight variations in mortar thickness, as you will find when you start laying both floor bricks and dome bricks.

[UtahBeehiver]

Going for minimal joint/almost dry fit is a great goal, I wanted to do this as well. Made a jig to do complex bevel and taper cuts (see attached pic). Spent hundred of hours doing this. At the end of the day and if I build another oven I would of only focused on the tightness of the inner dome joints only and let mortar be my friend on the back and back side of the bricks. No one ever sees these back and sides brick cut part of the build once you insulate. You can accomplish a very nice visual look and well as a structural strength by focusing on the interior brick joints. As you go up, you only need to bevel the first inch of so to achieve a very tight fit. See JR Pizza's build. But it is your choice. IMHO, your valuable labor hours would be better spent on other parts of the build.

[IH123]

I do feel that precise cutting and outcome may never happen however I really want to try it, at the end I never built a one before so likely will have to learn it the hard way. for my jigs, I will use my mitre saw to cut a piece of lumber to the correct angle, then attach it to my wet saw tray using strong clamps. I will have to produce one lumber jig for each cut. I forget to mention that with my 10" wet saw, I actually need two passes per cut on the thick side (as its depth is less than 4.5"), therefore I could end up having 16+ cuts/jigs per half brick -- I hope symmetry will help me cut that back in half to 8+ jigs only.

after I smooth and level the insulation layer very finely, which should almost allow me to lay bricks without any further levelling (while possible), I am going to practice on the simplest course,the spring line, and see how patient would I be and how much time it would take while doing it safely

Thanks so far for the recommendations, I always had them on my mind however wasn't aware of how difficult they could be. I will keep you posted

[david s]

The density of your bricks will be another thing to consider, particularly if you intend to do multiple cuts for each brick. They vary a lot, but medium duty are the most suitabl, especially if you intend on making multiple cuts for each bick. High duty are very dense, hard to cut and go through expensive blades quickly. This might be an important characteristic if you plan on multiple cuts per brick. Some builders have found them too hot. Low duty are very easy to cut, but at the other end of the scale are more prone to wear and can be not hot enough and lose heat too quickly. Medium duty as described by a supplier can vary from manufacturer to manufacturer. Reality dictates that you use what you can get.

FWIW my firebricks are 2290 kg/m3 or 2.29kg/L (you do the conversion if you work in imperial. They are not too bad to cut and produce a nice crispy base. Others may chime in with their brick densities, ease of cutting and cooking performance.

[UtahBeehiver]

If you go the route of precutting a wood pattern for you dome bricks, be aware the each course changes in bevel angle. I would suggest that you not cut a whole course of bricks at once, maybe 4-5 then evaulate how they fit and to see it adjustments need to be made. What looks good on paper does not always translate to real world construction. On a second note, as David mentioned, the brick hardness can effect wear on your diamond blades. I used super duty (surplus from an old steel mill, very high alumina content) and I went through a baker's dozen of diamond blades. I never have had any too hot issues with super duty bricks and once heated they hold the heat well.

[IH123]

I said earlier that I will keep the dome bricks floating on the insulation and so "(there will be parchment paper as a slip layer) but that can't level or added in layers as when it burns it could compress or dislocate."
I have changed my mind as I think when the paper burns it leaves gaps between the brick and the insulation top coat that gasses could leak out into dome render and exchange air leading to heat loss and also dome render insulation ceramic fibre mat fibre dust getting into cooking chamber from the little gaps. so I instead thinking of the following :


I will instead pad the dome bricks with very un-wet dry but little damp and VERY THIN refractory mortar such that its packed under the dome brick creating a tight seal, however it can't bond to the insulation coat properly that when dome expands if any cracks to happen they will occur on that not on insulation coat layer

but would the dampness from the head joint of the bricks fall down on that bed and wet it?might , but then I have to make it even more dry.


I today tried to smooth the insulation coat with rubbing brick however found about ~1/8" difference between right and left, so I wet it with damp sponge and I had set a level gaurd rails then I applied another 1/8" layer screeded and checked level with laser level it ends up perfect, picture below:






after 12 hours:

[david s]

The density of your bricks will be another thing to consider, particularly if you intend to do multiple cuts for each brick. They vary a lot, but medium duty are the most suitabl, especially if you intend on making multiple cuts for each bick. High duty are very dense, hard to cut and go through expensive blades quickly. This might be an important characteristic if you plan on multiple cuts per brick. Some builders have found them too hot. Low duty are very easy to cut, but at the other end of the scale are more prone to wear and can be not hot enough and lose heat too quickly. Medium duty as described by a supplier can vary from manufacturer to manufacturer. Reality dictates that you use what you can get.

FWIW my firebricks are 2290 kg/m3 or 2.29kg/L (you do the conversion if you work in imperial. They are not too bad to cut and produce a nice crispy base. Others may chime in with their brick densities, ease of cutting and cooking performance.

For what it’s worth my firebricks are2290 kg/m3 or 2.29 kg/L (you do the conversion if you work in Imperial). They are not too bad to cut and produce a nice crispy base. Others may chime in with their brick densities, ease of cutting and cooking performance.