Northern Ontario oven build

[MarkJerling]

Yup. I think you'd have to grease me up good to get me to fit! LOL

[Shawnr]

Getting there. I went from thinking I had way too many bricks to wondering if I have enough..:-O

A few questions
It seems like I am cutting large pieces (wedges) off of the 4 1/2" bricks as I get to the top. Does it make sense to start splitting them now? I am trying to reason it out and it seems like either works, but maybe narrow pieces would be easier to work with. There is one more course that I have since the last photo and it seemed to be quite frustrating. Maybe it was just me. Seemed like my visualizations were whacked. I noticed on some threads that I found with those interior roof shots that it seems like a transition to half bricks (half the halves....?) might be in order now?

I like the idea of a thermal break from the dome to the vent walls. How do the vent walls attach to the dome? I mortared the dome first course to the floor bricks so do I just do the same (to the floor bricks) since mortaring them to the dome arch would negate the effects of any thermal break, if I understand correctly? I found post #143 referenced here https://community.fornobravo.com/for...r-build/page10 . I cannot find a method of "sticking" the vent walls to the dome arch. Is there an adhesive here somehow? The tube of high temp or mortar?

I have laid out my vent landing floor bricks in the herring bone fashion but now see that most just line these up with the vent opening? Seems easier. My floor bricks are free to move now as they are only sitting on a sand/fireclay mix, although that is more sand than fire clay as I did not have much clay when I started. Now, after cutting all these bricks, I have lots from the saw. Do I use a "richer" sand clay mix to hold the floor bricks to the insulation board? And then mortar the walls to the vent floor bricks holding it all together?

[JRPizza]

Shawn, I tried to stagger my vertical joints to prevent a crack from running up the mortar, so every row I set had bricks narrower than the row below. When I got close to cutting half the brick off to get the width I wanted I switched to half bricks, then closer to the top 1/3, and at the very top back to 1/2. Whatever you need to do to reduce waste. Staggering bricks may look cool but I still got a vertical crack that actually split a brick or two.
Your vent, especially if you do a thermal break, will be free standing. Some have built part of the vent attached to the dome arch, which might give more stability, but also can subject the vent to thrust loads from expansion of the dome and allow for some conduction of heat to the vent. There is not a whole lot of data (any?) so you just need to pick a method and go with it. I built a freestanding vent with a thermal break. You can't have both - it's either attached or it's not. Most folks have opted for a thermal break and freestanding. I just read a ton of build threads and copied the folks that I was most comfortable following along with. As for vent floor bricks, I (again copying) went with a straight alignment. I figured I would not be catching them with a peel so alignment would not matter (and it has not). Also, because I used bricks and they really absorb drippings etc from cooking, I can easily pull them out, toss them into a very hot oven, and they come out looking like new (thanks Gulf for the tip)
I didn't use any leveler or adhesive under the vent floor bricks, but in retrospect I might have mortared the ones directly supporting the arches to get a little more side to side stability.

[Shawnr]

Thank you JRPizza That helps a lot. I noticed as I was going that some joints were lining up and, initially, cut a few bricks to cause an offset, then a few bricks later, the joints were lining up again. I figure (hoping) as along as the alignment spans no more than 2 rows, the support and strength will be there.

As for the vent, I picked up some of the fireplace rope today and will incorporate that into the vent opening somehow. As for securing it, not sure how I will do that yet. Since the dome bricks are mortared to the floor bricks, I might continue that trend. I am picturing mortaring the vent wall bricks to the floor insulation too though, just the bricks under the vent walls, not the middle ones. It kind of means the 2" rigid insulation is supplying the connection from the dome to the vent but with the weight of it all, I think this might work. Does that sound reasonable?

You have a great write up on your build! Thanks for the info in it. And thanks to those many others that documented their builds too!

Cheers,
Shawn

[Shawnr]

The dome is complete! Yay!

I have a piece of insulated chimney (6" with 2" wall) that I had planned on using for the oven. I would like to set the chimney back up the dome a bit, not quite at the top but not right over the vent landing area. I am wondering how I should do this. I have not seen this done too much. To make the vent (ductwork?) from over the landing to where I want the chimney to sit, is casting it the best way? Or use firebricks, cut to fit as necessary? Or steel ducting? If casting it, use castable refractory with reinforcing ie chicken wire? Would this makeshift ductwork be a good place to use perlite/mortar mix? Is this not often done for a reason? ie complications or just the hassle of building the ducting channel up the dome or just not a look most builders want?

As for a thermal break at the front of the dome where the vent walls meet it, I am wondering if sticking (via mortar) a piece(s) of insulation brick to the front of the dome arch would suffice as a thermal break? It would save a lot of cutting to insert the insulation rope into the vent side bricks and seems to make sense to me, although I have no idea if this is enough of a thermal break. I will go look up the thermal characteristics but wondering if anyone has done this. Considering that some builders use no thermal break, I would think it would be ok and then the fear of the rope fibers falling into the food would be alleviated. It seems like a lot of cutting of bricks to fit a rope in there, although that looks like a nice way of doing it too. Just thinking out loud and looking for input.

Re the comment earlier about sticking the vent lower bricks to the insulation, I mortared the bottom vent side bricks to the hearth instead of the insulation. I am not sure what CaSi board is like as my stuff (K Fac 19) is not that. Despite ordering the CaSi stuff, I was sent this other rigid insulation material that is like a thick buffalo board. Very soft. I did not feel comfortable building on it so cut the insulation back. This should be a solid base for the vent bricks. I ran out of 2.5" firebricks and the local supplier is currently out too so am building the vent out of 2" firebricks. Are firebricks necessary for the vent if a thermal break is incorporated into the design?

Thanks all.

Shawn

[Shawnr]

Regarding my previous post, I see that in post 7, UtahBeehiver mentions the terms Squirrel or beaver tail so I can try a search for those. Thanks. I had forgotten about that reply. Pays to reread threads sometimes I guess.

In that post, we briefly discussed outer dome coatings. I am wondering if anyone that lives in northern climates can comment on what they used and how it worked for them (or should I build a housing)

In a brief discussion with management this morning, we both agreed that we both like the dome look versus a housing. I have been planning on a housing due to our extreme weather here in Northern Ontario. (-40 in winter (occasionally) to +40 in summer (occasionally). I wonder if a stucco finish can take those extremes and still remain water tight. Any input?

[Shawnr]

Another question before I head back to work on the oven. When I laid out the floor insulation, I brought it right out to the predicted front edge of the vent floor landing. But since discussions have gone on about a thermal break between the dome arch and the vent structure, I am wondering if the insulation under the landing is not only not necessary but a bad idea, especially since my insulation is a rockwool product, as mentioned above. It seems quite hungry for water. (Picture buffalo board but 2" thick. )My reasoning being that if moisture ie rain gets into this area, it could wick deep into the floor insulation under the dome. I have seen some mentions of overhangs and of course the exterior door but thinking that removing this 2" insulation and replacing it with 2" firebrick (not mortared) might be a better idea....?

Any input for me?

[fox]

The reason for a thermal break is to stop to much heat loss going into the gallery section, so if you butt up fire bricks to the oven floor without a heat stop, then the gallery floor will suck up heat and espose to the air.
That is not unusual and many ovens operate that way, these things only really matter if you want to retain the heat for a long time?
So in the winter months you probably want to cover your oven with a tarp to keep the worst off the weather off the outside finish.

Different folk have different ways and ideas of how to seal the outside dome, where I live we use fibre cement, that is a 2-1 cement and fibre strands.
Our building trade just does not use lime in any exterior cement mix! You would get sacked of the building site if you did !
However it is obviously very different in other parts of the world as adding lime seems like standard practice!
Anyway I would suggest you see what is popular in your area and see how houses are plastered and with what.

[Shawnr]

Thank you fox . I was considering the thermal break around the walls but only recently realized the amount that would be absorbed into the vent floor so I will do something there. I am wondering if insulation firebrick is enough but since others have done the rope thing, I should go with that. We have lots of stucco houses in the area but since that is a vertical surface with building paper under it, if cracks develop, not a big deal. However in a dome application without the vapor barrier, I would think it is much more of a concern. To be safe, I think we will go with walls around the dome, cement board, then some kind of a stone or tile board on that. The walls will allow me to add extra insulation around the dome too so another benefit.

[fox]

I have used ceramic board for the gallery floor, covered with a piece of Stainless steel, just make sure the S/S does not touch the oven floor bricks.

[MarkJerling]

Regarding my previous post, I see that in post 7, UtahBeehiver mentions the terms Squirrel or beaver tail so I can try a search for those. Thanks. I had forgotten about that reply. Pays to reread threads sometimes I guess.

If you check out my drawings or photos, those show a squirrel tail design.

[Shawnr]

Thank you MarkJerling that is how I am leaning to doing it, using bricks to form the smoke channel.

[MarkJerling]

You're most welcome Shawn. It added a level of complexity, but I like the look of it. Some say it helps with heating the dome, but for me it was more of an aesthetic thing.

[deejayoh]

Regarding my previous post, I see that in post 7, UtahBeehiver mentions the terms Squirrel or beaver tail so I can try a search for those. Thanks. I had forgotten about that reply. Pays to reread threads sometimes I guess.

In that post, we briefly discussed outer dome coatings. I am wondering if anyone that lives in northern climates can comment on what they used and how it worked for them (or should I build a housing)

In a brief discussion with management this morning, we both agreed that we both like the dome look versus a housing. I have been planning on a housing due to our extreme weather here in Northern Ontario. (-40 in winter (occasionally) to +40 in summer (occasionally). I wonder if a stucco finish can take those extremes and still remain water tight. Any input?

Everyone loves the dome look, but it is very difficult to seal the oven in northern climate, especially with freeze-thaw cycles. You need a waterproof stucco, and you need to make sure that no water can get in around the bottom of the dome where it meets the hearth. I know @utahbeehiver's is a dome - covered in very cool copper shingles. You might take a look at that. Personally, I went with a housing as in Seattle we get too much rain to take a risk!

[fox]

If you dont want to cover your oven with a tarp over the winter then fiberglass coating over the dome will ensure there is no water penetration..
I offer this as a £300 extra with a terracotta finish but a DIY job would be around £75 for materials and will stand up to harsh winter conditions.
However I sill think covering any oven in the likelihood of snow is a good idea .