1st time build, Insulating the slab

[Oh Crap]

What I'm thinking is to cut off the chimney right where it meets the dome. Cut a firebrick to fit through, secure it using "Dinset" high temp mortar. Then make sure it's sealed properly and fill the remains space with vermicrete and then insulate the dome as discussed earlier. Hopefully that will sort out the top flue issue. After that I'd form an outer arch to house the new chimney, that may take some advise
thanks for all help so far

[SableSprings]

Glenn, it looks like cutting off just the top cap & dropping in a brick plug would be fairly easy for the top closure. I don't see any reason to take it off at the dome interface...just cut those couple weld spots to remove the top pipe section. You'll lose a tiny bit of heat out the top metal section, but good insulation (either batting or 10:1 perlcrete) on top would minimize actual lose of heat while firing or during use.

Since many builders are now separating their front entry/smoke collection flue system from the oven to further isolate (and insulate) the oven, adding the front extension would be doable. David S and others have done very nice, cast front flue systems that would work well for you if you wanted to try your hand at casting. Do you have room to extend out for the front arch & landing? Also, did you get the door with the kit? I'd be interested in how they set that up to mount on the kit's oven entry.

[Oh Crap]

Glenn, it looks like cutting off just the top cap & dropping in a brick plug would be fairly easy for the top closure. I don't see any reason to take it off at the dome interface...just cut those couple weld spots to remove the top pipe section. You'll lose a tiny bit of heat out the top metal section, but good insulation (either batting or 10:1 perlcrete) on top would minimize actual lose of heat while firing or during use.

Since many builders are now separating their front entry/smoke collection flue system from the oven to further isolate (and insulate) the oven, adding the front extension would be doable. David S and others have done very nice, cast front flue systems that would work well for you if you wanted to try your hand at casting. Do you have room to extend out for the front arch & landing? Also, did you get the door with the kit? I'd be interested in how they set that up to mount on the kit's oven entry.

Ok so I'm not crazy. It seems all is not lost.
I see what your saying about the cutting the top part off as dropping in a plug there. I could fill the remaining void with 10:1 vermicrete as insulation, at that point I'd begin insulating the dome with 2" ceramic blanket followed by 2" vermiulite, this should refuse potential heat loss around the remains metal. I plan then to render and finally tile it.
I'll have a go at anything once so I'll check out David's casting . Yes the oven base is 1m X 1m but I'm making the hearth slab 1.5x1.5 to enable a landing etc Yes the door came with the kit. I'll take some close ups for you to check out.

[Oh Crap]

1st pic is of the latches for top and bottom door 2nd pic is pic of hinge for bottom door, it's the same for the top door also. Appears to be welded on to the frame

[david s]

Although an up draft oven, with the flue in the centre of the crown of the dome is a little less efficient, because the flames want to jump straight to the flue, it does have some considerable advantages. Firstly the draw is very good, you don’t have any smoke issues at start up. Secondly, there is no flue gallery to have to work past, making access to the oven far superior, as well as requiring less real estate at the front on your supporting slab.

If the oven is to be only used occasionally rather than every day the extra fuel consumed is not really an issue. My first oven was an updraft one, based on ancient Roman kilns, it performed very well, but I now only build crossdraft ovens which do have superior performance.

In Pompeii I was surprised to see quite a few small ovens that used an updraft system, rather than a crossdraft one like that at the bakery. On contemplating this I came to the conclusion that these small ovens in homes were preferred so their homes didn’t get filled with smoke because they probably didn’t get used daily unlike the bakery oven that probably never cooled off and required better fuel efficiency.

To create a flue gallery at the front of your oven in order to convert it to a crossdraft system like most of the builds on this site will require design and construction as well as ensuring you have the required room in front of the oven to build it. You may be better off to use the oven as it’s presently designed, then maybe a year or so down the track, when you’ve had the experience to see how it fires, alter it with the knowledge gained.

[Oh Crap]

Although an up draft oven, with the flue in the centre of the crown of the dome is a little less efficient, because the flames want to jump straight to the flue, it does have some considerable advantages. Firstly the draw is very good, you don’t have any smoke issues at start up. Secondly, there is no flue gallery to have to work past, making access to the oven far superior, as well as requiring less real estate at the front on your supporting slab.

If the oven is to be only used occasionally rather than every day the extra fuel consumed is not really an issue. My first oven was an updraft one, based on ancient Roman kilns, it performed very well, but I now only build crossdraft ovens which do have superior performance.

In Pompeii I was surprised to see quite a few small ovens that used an updraft system, rather than a crossdraft one like that at the bakery. On contemplating this I came to the conclusion that these small ovens in homes were preferred so their homes didn’t get filled with smoke because they probably didn’t get used daily unlike the bakery oven that probably never cooled off and required better fuel efficiency.

To create a flue gallery at the front of your oven in order to convert it to a crossdraft system like most of the builds on this site will require design and construction as well as ensuring you have the required room in front of the oven to build it. You may be better off to use the oven as it’s presently designed, then maybe a year or so down the track, when you’ve had the experience to see how it fires, alter it with the knowledge gained.

My original plan was to build a 1500 sq stand and slab. The reason being I wanted to add a landing . The oven base is 1000 sq thus giving me the room to build said landing. So the room is there to add a flue gallery but the knowledge is just lagging behind ("

[SableSprings]

I agree with David, being able to close off the top vent so you can bake with retained heat and optionally still use an active fire for pizza might be worth experimenting with. Getting a feel of how and how often you're really going to use the oven would be valuable info to have before doing any major addition/modifications. Just closing off the top vent and having your exhaust come out the oven's front does create a crossdraft oven...just a little sooty in front above that nice door (and that soot does come off with a little damp cloth work).

Most of us seem to end up spending a fair amount of time using the oven before actually finishing the outside anyway, so if you could insulate and protect that insulation from getting wet before making changes, you might have second thoughts on how you want to proceed. As David said, it will work fine as...just not as efficiently.

Making sure to have adequate base insulation to set the oven on and keeping it dry are really your most important tasks at this point.

[Oh Crap]

So, proceed to plug the existing chimney and insulate as discussed then add my finishing to protect it all. The lack of chimney shouldn't have any adverse effects, other then soot, but will act as a cross draft oven thus allowing me to cook pizza and then use retained heat to cook other dishes, with door closed obviously. Then decide if I want to add in a chimney and landing later.
the main thing I'm getting is too plug chimney and insulate well. That could make my life easier lol

[Oh Crap]

So things are about to start materials for the support stand and slab are arriving this week, planning on commencing work over the Christmas period. I’ll start a different thread and picture document it there. BUT I need a little bit of advice again. I have CalSil board coming 60mm, but I was originally going to do a 100mm vericrete course to sit CalSil on. I’ve come across thermal blocks and am wondering would they be a good substitute for the vermiculite course? I’m not well versed on insulation terms Heres the link to the blocks themselves.............

[Gulf]

I'm not very good with converting the many different measurements that are used worldwide for compression strength and thermal conductivity. However, from my memory of past discussions, I believe that compression strength for aircrete is well above what you would get with vermicrete but, the insulation factor is well below. That may not be an issue since you have a little over the minimum of 50 mm of CalSil that is recommended. It's best that you wait for the engineers on the forum give you a definitive "pie R square" .

If it has not been covered above, I would like to remind you about the weep holes and elevating the insulation above the structural hearth. I now like the grid pattern that mosaic tiles offers.

[Oh Crap]

Well after a few months of bad weather and "other" delays I finally got started. Poured the base foundation yesterday and now just waiting for it to go off to start the block work

[Oh Crap]

So after a looooong time I'm pretty much finished
a few small bits to tidy up this week but we're eating pizza and have made bread, roasted chicken and beef for the following days dinners.. thanks for all the help and advice
I tried to resize picture but couldn't here's a link to them.
https://photos.app.goo.gl/u3H1VYdCN6uT8gi48

[Oh Crap]

I know the chimney is wrong but it still works for my needs, I've roasted and baked in the oven after pizzas are done.
THe oven is sitting on a layer of broken tile, 4" insulated block, 2" ceramic fibre board then the oven. The dome is insulated with 3" ceramic fibre blanket, 3" vermiculite (10:1) then plastered, waterproofed and finished in slate which was then waterproofed aswell. It takes 90 mins to get up to cooking temp and pizza's are done in 90 secs or less.. it is still warm 2 days later..☺️☺️

[Squirt Reynolds]

If you have not already, download the eplans from Forno Bravo, it is a good design and construction baseline, a little dated but a good start.
Most questions are answered there or in the blog by using the search function.

Ceramic "blanket" is NOT used under the floor only over the dome, it is too soft. Do you mean CaSi board.? Do not place aluminum under the floor, it will trap moisture and also has a very high thermal transmission factor (K value). Again most question are answered in the eplans or the blog.

good answer, thanksI was going to do a 1” heat board and then couple inches of very/cement on top. With a layer of alum foil between the two, you now say not to. What’s an alt to separate the board from cement while drying?
thanks