Ope-dog's 36" Oven .. (fingers crossed!)

[Ope-dog]

Hello Forno Friends! After a long (and busy hiatus) I was finally able to get my attention back on the WFO. It has been great to work on it over the last few weeks and yesterday I was able to get the dome complete! A great feeling for sure!

The build was pretty straight forward thanks to the many threads and feedback on this site. I was able to use the IT until the last 2 courses, and after that there was still a bit of trickery to contend with. As my arch design got changed at the last minute (due to poor pedestal planning!) I opted to not worry about a tapered arch and just tried to build into is as best I could. While the dome/arch transition looks pretty .. well.. horrid, the good news is that the arch isn't so large, so apart from me there's very few people that will actually turn their heads and stick it in to see said transition. So I'm not going to lose any sleep over it!

Once the IT was retired, I used a jack stand and a wooden disc on top. I didn't want my dome to flatten out too soon, however, so I opted to go with a "folgers shim" to keep the bricks angled on the trajectory, or close to it. What I found quite difficult at this part was a) getting the bevel angle where it needs to be and b) not having the visibility from the underside. What ended up happening is the 1st course using the folgers shim came out fine. The last course (before the plug) I used a plastic cover that from a tape container. However I had no idea that the ass-end of these bricks was sitting lower than the "folgers" course. So when the jack stand was pulled out and the dome was exposed in all it's glory, I had the baby course surrounding the plug about a half inch lower than the plug and rest of the dome. It almost looked like the entire course slipped (which it didn't.. it was just laid wrong.) So I hit it with the grinder best I could. While it doesn't look great.. it looks a bit more level and kind of has an "aged and weathered look" to it. (Yeah, I'll go with that..)

[Ope-dog]

So.. next steps... insulation and chimney build. I have decided that I will build a pergola over the WFO and smoker, however that won't happen for a little while yet. (The winters in the NW are too wet and chilly... it seems when brick gets wet it takes forever to drive the moisture out - a cover is thereby necessary.)

Yet another chimney question: My original build was going to be a chimney, shorter in stature (12-18" above dome) and built with fire brick. However, now that I'm going to incorporate a pergola, I will need to switch to a steel flue. Is there any harm in building up my chimney to the anchor plate position and then doing curing fires and even burning the oven before the flue gets placed? Apart from the drawing properties changing when the flue is in place, I cannot think of any issues, however that certainly doesn't mean there aren't any. If anyone has any thoughts, or has done a chimney extension at a later date, I'd be happy to hear from them!

Also, is there any advantage to bringing the insulation blanket up around the sides of the vent / entry? I have noticed a lot of builds don't insulate the vent, however assuming I'll have extra material I didn't know if there would be a drawback to it or not.

Like most users, I want to echo the appreciation for all that have weighed in with thoughts/ideas/input on the build. Certainly some mistakes were made, however I am pretty excited to move into the next phase and hopefully get some flames in this thing in another month or so!

[Ope-dog]

Some pics of my building process...

[DrScott]

Looking good!!!! I'm building up my stand now as a trial fit before I start framing and pouring.

[MarkJerling]

So.. next steps... insulation and chimney build. I have decided that I will build a pergola over the WFO and smoker, however that won't happen for a little while yet. (The winters in the NW are too wet and chilly... it seems when brick gets wet it takes forever to drive the moisture out - a cover is thereby necessary.)

Yet another chimney question: My original build was going to be a chimney, shorter in stature (12-18" above dome) and built with fire brick. However, now that I'm going to incorporate a pergola, I will need to switch to a steel flue. Is there any harm in building up my chimney to the anchor plate position and then doing curing fires and even burning the oven before the flue gets placed? Apart from the drawing properties changing when the flue is in place, I cannot think of any issues, however that certainly doesn't mean there aren't any. If anyone has any thoughts, or has done a chimney extension at a later date, I'd be happy to hear from them!

Also, is there any advantage to bringing the insulation blanket up around the sides of the vent / entry? I have noticed a lot of builds don't insulate the vent, however assuming I'll have extra material I didn't know if there would be a drawback to it or not.

Like most users, I want to echo the appreciation for all that have weighed in with thoughts/ideas/input on the build. Certainly some mistakes were made, however I am pretty excited to move into the next phase and hopefully get some flames in this thing in another month or so!

Your build is coming along nicely. Well done!

I can see no reason why you can't fire with a short chimney in the mean time. A taller chimney will draw better so you may consider getting your flue pipe now and working around it or doing the flue later.

I think insulating the whole thing works well. Certainly, with mine, I insulated right out to the front opening and my oven holds it's heat well.

[Ope-dog]

Well, "phase 2" is almost complete. Really looking forward to "phase 3" (curing fires and chimney final rendering/veneer) and getting over this hump. The insulation actually was much easier to manipulate than I was expecting. But the v/p mix.. holy crap! This stuff is unruly and obnoxious for sure! I started with an 8:1 mix based off reviews I've read about getting the better insulative properties out if it. But it was just too unmanageable. I was somewhere in the 5:1/6:1 mix after the initial batch. I also opted for the 50/50 v&p as I've read other posts where you can get the best of both worlds. Bags were the same price basically at Big Orange, so what the heck.. why not..

I found in the early going as I got half-way up the dome I lost entire sections when a spider farted on the other side of the dome. Then I tried the "ramp" method where I went up at an angle, building on top of the previous layer. (I imagine this is how the Egyptians built much larger structures back in the day.. lol) This had more success for sure. Of course, due to my piss-poor planning last year, I have to build out the counter top around the sides and rear of the oven to support the rendering portion of the oven. So.. no ramp method there!

Once you start to crest the top of the dome it was absolutely smooth sailing. At the end of a long day, I was out of energy and out of time so ended up just plopping the remainder of my mix on top. I'll concentrate on the backside on my next trip up. My goal is to get the v/p mix up on Saturday.. then let it set for a week and start some curing fires the following week.

I had started to put some old chicken wire over the dome and that became quite the adventure just in itself. I've read where other builders have opted against the wire and decided I'd try w/o and go with my wire tie-downs instead. I imagine this could be some of the issue with my p/v mix not holding too well. I guess the real test will be when I go back in a few days and see if it's crumbled and fallen due to the drying process.

Chimney pipe will be placed inside the initial chimney build-out you see pictured. I'll get an anchor plate and then build up around it for a spell. Because this area is already done up with a lot of matte black fixtures, I didn't want to go with a stainless chimney pipe. I also was having trouble finding a double wall chimney pipe in black and didn't think it would work too well to paint a stainless. My plan is to build up around the pipe (once inserted) an 8"x8" chimney, then when the 6" pipe is placed inside this brick chimney I will back-fill the gaps with v/p mix. Considering this is an outside structure and no real combustibles will be in proximity to it, I think this layer of insulation should suffice in terms of keeping the chimney pipe from cracking.

Any feedback on the above, or if anyone has tried this method and cares to weigh in, is always greatly appreciated!

More to come!

[Ope-dog]

@Dr Scott.. take my advice.. double and triple check your stand dimensions!!! You're going to have a lot of fun I'm sure!!!

MarkJerling, thanks for the compliments. I may end up just building out the entire chimney in parallel with the outer veneer. Not sure yet. Any harm in building it out in parallel with after a curing fire that has burned down or is it better to have the higher chimney curing in the same fashion?

[MarkJerling]

@Dr Scott.. take my advice.. double and triple check your stand dimensions!!! You're going to have a lot of fun I'm sure!!!

MarkJerling, thanks for the compliments. I may end up just building out the entire chimney in parallel with the outer veneer. Not sure yet. Any harm in building it out in parallel with after a curing fire that has burned down or is it better to have the higher chimney curing in the same fashion?

Are you suggesting a tall brick chimney?

[Ope-dog]

MarkJerling , sorry for the confusion. I'm thinking to go another course or two with finishing brick and then leave the rest of the pipe exposed. I don't want to make this area too heavy but in essence would look to make 1/3 or so of the 4' pipe double walled.

I'm not opposed going back to the drawing board if need be. Better to kick the tires now on idea than have a cracked pipe in a few months.

[MarkJerling]

No problem. I used a pretty tall stainless steel flue and it certainly worked well. I don't see the need to have the flue in place for your curing fires but in my case I found it easiest to have it in the final position from the start.

[mongota]

I think you and Mark nailed it.

You can fire without the chimney, but you'll get a better draw with one. Without the vertical draft, when you start your fire you'll likely get smoke wafting out the front of the oven and some going up the flue versus it only going up the flue.

I had additional blanket insulation, I did 4" over my dome and 2" over the vent. I had enough to do 4" over the vent, but oddly it was an aesthetic choice...with a total of 4" of blanket over the vent, the front of the oven sort of got too bulky and puffy, lol. So I used 2" over the vent.

The vent includes the flue and chimney, so insulating it, it's not that I'm really keeping it isolated from the outside atmosphere. For me it was sort of on the idea that I'm minimizing the temperature differential between the dome and the vent arch, which might help minimize differential movement. My vent arch is physically uncoupled from the dome, but what the heck. The things we do, you know? Try to make it better without going to far off the better-to-betterer cliff.

[Ope-dog]

Well, managed to get the V/Pcrete rendering completed today. It was a bloody nightmare putting that stuff up. I lost a patch on the backside.. twice! How frustrating! I found that as I went along, I would get a little too confident, and start placing/patting the globs a bit too quick and forcefully. Slow and gentle really is the mantra when applying this stuff. I was tempted to put a skim coat of mortar over everything, however as fragile as the render was being I didn't want to fuss with it at all. The parts that I had applied on Wednesday had already set up quite nicely, so I'm expecting good things when I go back next week.

I did have to cheat a little bit on the backside where I kept losing a bit patch. I ended up placing some chicken wire mesh in there, and then on top of that grabbed some grass trimming and mixed them in with my mix to help stuff bind a bit. (I figure it will eventually burn off,.. should act no differently than straw would on a cobb oven, I reckon.)

So now I'm a bit torn on the sequence of my next steps and would love more input if anyone has any.

1. Do I do curing fires next for 7 days and THEN put on a mortar/veneer finish?
2. Should I do the mortar/veneer first and then curing fires?
3. Does it really matter.. and is there any harm in doing curing fires for 2 or 3 days..then let the oven set.. and then pick up a week later?


mongota , I went back to revisit your amazing build. Seems you skipped the obnoxious p-crete step all together and went right to the stucco. I'm wondering if I should have attempted that, given I have extra blanket from my build. I'm mostly bummed that I lost my perfectly nice little "dome" shape. Hopefully my final render layer I can get it back in to a somewhat round shape.. I also noted that it seems your curing fires were a bit spread out as well?

[MarkJerling]

To answer:
1. Curing fires first. Doing curing fires first makes it easier for moisture to escape.
2. No, as stated in 1.
3. If you pick up a week later, then you should continue with the curing fires.

[Ope-dog]

Thank you, MarkJerling . I was pretty sure based of other threads that curing fires was next.. but.. there is some information out there that would lead otherwise.. so wanted to make sure. Like everyone at this stage in the game, there's been too much sweat, smiles, and swears to this point and would hate to screw it up now.

[DrScott]

It looks Great!!! I hope the fires go well!!