Northern Ontario oven build

[david s]

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!

Any totally waterproof coating will not only keep water out, but also prevent moisture being driven out. Italian ovens are traditionally out in the weather with a porous lime based finish which allows the outer shell to breathe. This probably suited most of Italy, but the prevailing weather conditions in other places might mean a different approach. We live in the dry tropics and for most of the year a porous outer shell would be the most suitable, but during the wet season the oven is better to be waterproof, although I’ve experienced times when the oven will pick up considerable moisture from the atmosphere even if it actually hasn’t rained as our summers will often have high temperature accompanied with continual 95% humidity. Not waterproof coating will be of any use in that scenario. The best solution apart from an oven enclosure is probably to leave the outer porous and have a roof over the oven. This of course means more labour and expense and for most not worth the trouble. My own solution is to apply a cheap, very flexible, acrylic, hi build, waterproof product that was developed to coat the ridge cap mortar on tiled roofs. It is called, in our country, Flexible Pointing, designed to be troweled on I find it easier to paint it on in around 3 coats by diluting it 20% with water. This results in a finished coating of around 1.5-2 mm thick and copes well with expansion.

[Giovanni Rossi]

I always pay close attention to discussions about this part of the build. Thanks to all who comment. Want the dome look and will be building in Central PA, USA...lot's of adverse weather! Fox, really like the look of that oven.

[UtahBeehiver]

Consider a dome vent at the apex of the dome. Water will get into the dome not matter what you do, so when water sublimates to steam, the volume increases by 1500 times building up pressure under the dome's coating which could possibly lead to cracking. There are dozens of different styles of vents builders have concocted over the years, Gulf and I just used a cheap auto hydraulic breather vent you can get at any autoparts store but you need to plan ahead. It requires a 1/2" FPT bushing be set in the stucco or finish material.

[Shawnr]

Thank you all for the input. I have decided on a housing.

I had a major disappointment yesterday. Many of you might have noticed from photos I have posted and been too polite to mention it. As much as I was aware of not lining up brick joints, and thought of it with every brick, I either was too focused on the joints or am just a dumbass. I did cut several bricks to avoid this exact situation, but obviously, not enough. Looking at my dome, one would think I was trying to line the joints up, the absolute worst being right up the middle of the front. Obviously, very poor construction but at this point, I am not about to bust it up and start over so I guess my project will be a test oven to see how bad it can be and if it will collapse on me. The oven integrity will rely on the design benefits of a dome, rather than the mortar. Yea, yesterday was definitely a bummer day. And in doing the squirrel tail venting, it seemed to go south on me too. I am fairly handy, usually, with metal and wood but starting to think brick work is not for me......

Today, I had a better day. I made a mold for the vent and cast it. I have spent way too much time trying to figure out how to use bricks to transition to the vent channel up the dome but thought a cast would be too difficult. turns out, it went way faster than the days I have wasted trying to figure out the other way. So today, I worked more on the squirrel tail, removing what I did not like that I had done yesterday and redoing it. Then reworked my chimney ideas. As for the joint up the middle of the front, I put some chicken wire embedded in mortar up the middle, like a bandaid. I don't really think this will do much but maybe better than nothing. This is also the channel for the ducting so hoping that it makes the area stronger for the temperature changes it will see. I think it will the first part of a cold dome to see heat since the hot gases will be exiting there immediately. Not a good place for a compromise! If anyone has other suggestions for me, feel free to chime in. I will try to have a thick skin....

So, having said that, to attempt to build an exposed dome in our climate would really be challenging a dome that I think is already compromised. But management and I spent some time looking at completed ovens and we are coming up with a vague plan for a housing. I have steel studs and cement boards on site so hoping to start that part soon. Weather here has been great for an outdoor project. I did not expect to get this far.

Thanks all.
Cheers,
Shawn

[MarkJerling]

Now that you mention it, I see the bricks lining up. I did not notice it before. I imagine you'll see a crack form there, but I'd be very surprised if it will fall down on you. I think a small crack will not cause it to fall down.

[Shawnr]

Thanks Mark.

As I am obviously disappointed, I have been wondering (kicking myself) how I could go so far south on this criteria that I knew about. I then recalled from building that it seemed that the seams seemed to align on the inside or the outside, probably something to do with my cutting of the bricks (could have done better?).
Going back to post #32, the shot of the inside, the seams look much better so I think that is what my focus was. If the outside aligned but the edge of the brick sat mostly on or near the middle of the brick below it, then I stuck it in place. Where I could not get that, I cut a brick (most of the time...?) so I will try to relax a bit. As I said, not much to be done with it now but for other new builders, maybe this will help them out.

Regards,

[UtahBeehiver]

Due to the shape of the pompeii ovens, they are self supporting. You may seem some cracks but I dare say the almost every oven has cracks and if the builder says his or her oven is crackless then they are a politician or a used car salesperson. But that said, there is a lesson for future or current builders, you cannot judge the interior joint alignments by how joints look on the outside.

[MarkJerling]

Thanks Mark.

As I am obviously disappointed, I have been wondering (kicking myself) how I could go so far south on this criteria that I knew about. I then recalled from building that it seemed that the seams seemed to align on the inside or the outside, probably something to do with my cutting of the bricks (could have done better?).
Going back to post #32, the shot of the inside, the seams look much better so I think that is what my focus was. If the outside aligned but the edge of the brick sat mostly on or near the middle of the brick below it, then I stuck it in place. Where I could not get that, I cut a brick (most of the time...?) so I will try to relax a bit. As I said, not much to be done with it now but for other new builders, maybe this will help them out.

Regards,

No worries Shawn. I have a few places in my oven where, purely per chance, some bricks line up. My oven has three small cracks but it makes absolutely no difference to the overall strength or function of my oven.

[Shawnr]

...... if the builder says his or her oven is crackless then they are a politician or a used car salesperson. .

UtahBeehiver lol...

Again, thanks guys.

Had a good day yesterday, mostly. Picked up chimney parts which helped me finalize my chimney plans. It seems a lot of this project is winging it as I go but I guess that goes hand in hand with unchartered ground, as this project is. The chimney mount is defective, which I did not know until I tried to attach the chimney to it but the store is replacing it for me. It is missing the groove for the locking band to grab. At least having it on site allowed me to move forward.

I mostly finished off the brickwork to form the vent up the dome. I have been planning on putting firebrick across the top but with the discussions about movement and cracking, I wondered if the firebricks could crack and fall into the vent so decided on placing a piece of stainless into the sides to form the top, as shown. . It will not be physically fastened to the bricks so can move but will be installed in a way that it cannot slide out. I will contour it once the chimney mount and vent are in place. I also reinforced the brick sides with mortar and fibres on the outside of the vent. I could not find pics of finished squirrel tails. MarkJerling I saw your pic but only the sides in place.

I took the forms off of the cast refractory vent. I am pretty happy with it but might not know any better. It looks functional, exactly what I wanted. Getting that sometimes surprises me... I thought I tapped the heck out of the from when I poured but obviously, not enough or the way I built the form would not give me that nice smooth look. It will be totally hidden anyways.

So when I get back there, I can finish the chimney install, insulate and start framing the sides. Daytime highs are still looking good for the next week or so. Weather has certainly been in my corner this fall. We should be scraping frost off the car windows in the morning by now.

[MarkJerling]

Here's the only two photos I took of that phase, sorry.





And the oven drawings has a cross section that shows it all quite clearly. So far the fire bricks have spanned across quite nicely. If there's ever a collapse, I'll need to open it up from above and find another solution. I like your stainless steel idea.

[NCMan]

A question I have for the folks doing/building a squirrel tail chimney......other than having it exit out of the dome center, what is your reasoning for it? I just always wondered that(?) Nothing wrong w/it at all, just wondered.

[Shawnr]

Thanks again MarkJerling I had not seen the one showing the top on. It looks great, looks more substantial than I pictured for some reason. I probably worry too much but knowing the guy that built my oven, well.....

Great question NCMan ! For me, I felt like the chimney up front would be towering over me. Not really true as it sits back a bit anyways with the tunnel landing, but I just wanted to move it back. And since I am doing a "dog house" over the oven, it allows me to put the chimney centered in the peak front to back, (more or less) which I pictured being a little easier to frame than right at the front. If I had done an exposed dome, I would have probably kept it at the front cause I like that look.

It does not seem to be done very much. Not sure if most just like the chimney at the front or don't want the extra headache. I did waste hours trying to figure out how to do it, but I tend to overthink things before I make my mistakes...(yes, not a typo )

Cheers,

[MarkJerling]

Thank you Shawnr . It sounds like your guy works a bit like my guy! LOL

[MarkJerling]

A question I have for the folks doing/building a squirrel tail chimney......other than having it exit out of the dome center, what is your reasoning for it? I just always wondered that(?) Nothing wrong w/it at all, just wondered.

I read somewhere that a squirrel tail chimney design helps to heat the top of the dome more quickly. I have no idea if that's true, but that was not my primary motivation: We have a window to the side of the oven and I wanted the chimney to be clear of the view out the window.

The other reason is that I have a "know it all" friend and I knew that he would tell me that the flue out the top of the dome was wrong and that I'd lose all the heat out the oven. So, of course, it was fun to have a bit of fun with that.

[Shawnr]

I completed the vent, insulation and moved on to the framing and roof structure. When I started fitting the steel in place for the vent, within the sides, it looked like I was going to be restricting the size of the vent a lot so I rebent it and placed it on top of the sides. I built a small "test fire" and I seemed to be getting a lot of smoke out the front but in fairness that day, the smoke that did come out of the chimney, came down anyways, so conditions were not conducive to a good test. I also had only kind of placed the cast vent up against the dome. Since then, I mortared insulation bricks to the front of the dome, and then place the cast vent up against that and made a better seal. I think it all helped a bit. I also have not completed the landing arch so I tried playing around with options there but it seemed to still smoke out the front a bit. I am hoping that when the landing arch is complete or a decent amount of heat is built up in the oven, that the chimney draws a little better. I know I can add a 1 foot section of chimney to the top as a last resort but the boss girl already does not want it any taller. Negotiations will continue into next summer...

3 layers of insulation went on, metal studs in place and cement board sidewalls in place. Soggy weather here last couple of weeks and I have been working around that but a few nice days ahead. I probably should have erected a canopy but almost done now. The rainy days have been few until the last couple of weeks.

I have been building a few small fires and moving them around while I work. Just building the fires is kind of a reward for the work so far.

Cheers,