32" build in Calgary, AB - pompeii neapolitan

[IH123]

as the wet cure and staged drying phase is over, I today got the slab uncovered to get it baked and dried in the sun. did initial marking for the oven foot print:

[IH123]

The perlcrete layer over the dome is to shield the 2" ceramic fibre mat ( which is the primary insulation for dome shell) from the elements and provide additional insulation and rigidity/strength. after this layer, I plan to cover it with whatever it needs like thin stucco (not sure yet would research it) however I know I need to put on top most a type of breathable paint that repel moisture but let steam escape. The best of them all is I would be creating an aluminum sheet shingles roof gore made like orange peel shingles around the dome shell with about 1" gap from the outer most layer of the igloo. There will be about 6-8" aluminum sheet (not foil, real thick ice/snow/hail proof sheet , I think the ones I have 24 gauge) wrap over allover the dome and part of archway, this will be spaced from the igloo of the oven by stainless steel screws and bolts with screws erecting from the aluminum sheet toward the igloo to keep at at at least 1" distance, then on above this I will make another warp (which will be smaller diameter however it will overlap covering the top of the bottom wrap by at least , lets say 4", and keep wrapping in an orange peel de-peel like shingles (aluminum sheet shingles) until I reach the peak of the igloo, that's when I do not wrap, I leave a big hole lest say about 4-6" without any cover; however, on top of it , I lay down an umbrella with larger diameter , lets say 8-12" with cone shape (like a roof flashing however perfect cone all over ) , which will let air escape out up in the air and prevent water and snow melt getting in, this will also allow cold air to flow from under the wraps upwards keeping the igloo shell dry as it allows fast evaporation as it heats flow upwards through the umbrella opening.of course, an alternative is standard roof covering the entire oven floor print and possible siding, unless roof is very large, in Calgary winter, snow could fly meters away horizontally from wind so either siding or big roof.

[david s]

the purpose of the 1/8" refractory mortar is to seal the fibres and dust form the boards not structural or levelling, as long as it dries and not flakes out then it would have done it purpose (consider it rigidizer and seam glue). I am not using any percrete for the floor insulation, those vertical ones or for the dome render.

Yes, your attached plan clearly shows it to be outside the dome insulation. Is tha perlcrete layer for additional insulation or for strength? What is the purpose of a thick 5:1 layer over the blanket insulation? Do you plan on covering it with anything?
your planned oven floor working height should work out to be ideal.

[IH123]

it looks like my concrete slab top surface on top levelling layer is 39" above the bottom slab surface (and almost same from the pavement in front of it, may be ~40":

[IH123]

the purpose of the 1/8" refractory mortar is to seal the fibres and dust form the boards not structural or levelling, as long as it dries and not flakes out then it would have done it purpose (consider it rigidizer and seam glue). I am not using any percrete for the floor insulation, those vertical ones or for the dome render.

[david s]

I’ve already posted what I think about the stainless bands around the base of a brick dome hemisphere, the use of aluminium foil and the need for weep holes and lifting the underfloor insulation to provide moisture pathways to them, so I won’t repeat my cautions. Two additional things to consider are
1. applying a thin refractory mortar layer over dry highly hygroscopic insulation is nigh on impossible as it dries almost instantly making an even layer impossible.
2. A thick 2-4” vermicrete contains a very large amount of water ( do the volumetric calculation at. 40% water) most of which remains as free water which is problematic until removed. 5:1 is not particularly a great insulator (1/2 as good as blanket) and also not particularly strong. What are you trying to achieve with this layer? Will anything else be applied outside it?

[IH123]

I think I have made my mind on final insulation stack. I hope it will work. what do you think?

[IH123]

Here is how my foundation looks like after removing all the lumber work-forms. I will use grinder to grind the edge and corner surface as its a bit rough, might smooth the levelling layer gently as well because when I protected it with vapour barrier after pouring (trees where shedding spring things did not want the surface get sprinkled with them for 4-6 hours until its sets) it spoiled the smoothness of the surface very tiny (not mechanically relevant but smoothing it would be very easy to smooth , can be even done with an edger without any grinder here to keep it gentle or with a sand paper)

[IH123]

Can't remember if we talked about a tapered inner arch configuration. Takes a little more work up front but makes the tie-in of the dome to the inner arch more precise and easier.

Yes, thanks for the extra photo, we talked about it on here earlier. Having it on the right angle helps making the dome and arch curves intersect as an arch into compression perpendicularly for their joint surface.

[UtahBeehiver]

Can't remember if we talked about a tapered inner arch configuration. Takes a little more work up front but makes the tie-in of the dome to the inner arch more precise and easier.

[david s]

If you are concerned about a smooth flow of exhaust, laminar flow and turbulence, a smooth surface as well as appropriate form are the primary considerations. Just as the form and the surface of a yacht hull are the most important factors in reducing drag, in this regard a smooth round stainless pipe is far better than a square chimney (round best square second rectangular last. The inner surface of the pipe presents far less drag than the rough lumpy surface of a brick chimney. Stainless pipe first, cast surface second, brick surface last. Of course soot build up alters the surface and introduces increased drag, but I’ve never heard of anyone cleaning their chimney in order to improve the draw performance, it’s usually done to reduce them catching on fire.
The flue gallery however, is an area that can greatly benefit from a decent form and attention to inner surface, just as well designed headers that replace the standard manifold in car engines improves breathing and therefore performance. The form of an inverted funnel allows for better smoke collection and a smooth flow to a smaller cross sectional pipe or chimney. If the flue gallery is made from sheet stainless, it is quite light which reduces the heat sink effect of a brick gallery. A cast form, whilst heavier than a stainless one, but if thin is still considerably lighter than a brick one can easily form compound curves not possible for brick units. So if it’s efficiency you’re after a stainless form is first, cast gallery second and brick gallery last.

[IH123]

I am planning to shape the inner arch (throat) bricks so that they facilitate the smoke move to the flue gallery without swirls, by curving the brick so any 90 degree edges becomes curved:




How it may work: Air hits top thin micro layer inside will swirl and push the air upcoming down which will exist without swirling (colliding) on the brick and as it exists from under the arch there will be even a more steep slop to help vacuum suck it up on a circle arc instead of it has to bloom before escaping , therefore least if not none of flame or smoke escaping to oven mouth .

[IH123]

My little practice to confirm theoretical brick count for first few courses :very untidy and out of order as the cuts are very not precise at that scale; however it helps someone know how and where to start:

[IH123]

removing the workform lumber, slab needs tiny smoothing on edges and corners otherwise appears really solid and dense

[david s]

My feeling is that the insulation boards are better left unsealed. Once they’re covered with the floor bricks there’s no chance of ingesting or inhaling anything. Look at the MSDS sheet for those products to learn about any toxicology.
It is accumulated moisture that is the main problem. Any coating applied will probably not seal 100% and even if it does, the effect of abrasion and heat may provide an entry for moisture. A sealing layer can work equally both ways, making moisture more difficult to exit. This is why I prefer some space below the insulation where both heat and pressure can drive the moisture south.
By all means try you sealing method, but maybe try at least to obtain a product that can withstand the heat (400C)