Challenges and progress of building pizza oven on a slope

[Yokosuka dweller]

Managed to make some tricky cuts to interlock the serpentine somewhat with the arch on both sides. Hope this holds up. I wonder if I could get away with a brick chimney, even if it were a little short - instead of the SS pipe...We will see...I'm way in improvi-land as it is...

Flue opening measures roughly 11cm * 14/15 cm which is 154-165cm2, for my 32" oven I should be at 175cm2 so a little on small side...

[Yokosuka dweller]

Put a few more bricks on the flue/chimney and also used angle grinder to make the existing flue passage slightly bigger. No problem worked out.

I bought a 24" Selkirk chimney, chimney top and anchor plate online. With the current situation it will probably take a looong time before it arrives here.

Yes, 24" is probably too short but the brick part of the chimney will be around 10" and the chimney top cap is also around 10" so altogether the smoke stack will be around 44" or 111cm, so I hope that would be enough to let my 31" dome breathe.

Cut some more brick and did a dry run for the brick course that will house anchor plate for double wall chimney. Ground some of the bricks round in 15" diameter to fit the bottom of the anchor plate.
JR Pizza used bolts to fasten the anchor plate, others as far as I can see, used masonry screws. I'm not sure yet what I will do. In any case, if its bolted, then I need to cut a slot in the bricks that sit on top of the plate to keep room for the bolt head/nuts isn't it?

And, two of the bricks I cut are reclaimed, they don't look too good inside, kinda looks like the firebrick is pulling apart. I may find some denser bricks and redo this cut.

[Yokosuka dweller]

Nice weather today. My insulating blanket arrived the other day and I threw on some gardening clothes and a 3M facemask (they're hard to find these days...). Blanket dimensions were 61cmx2,5cmx7,2m. For my 31" dome I got a full 2 layers, i.e. 2" thickness and a bit leftovers which I threw on top of the dome and kept a piece for an oven door later on.

Also put on the chicken wire. I think its reasonably round, but 4-6 cm pf perlcrete, which I plan to put on next will help with that. So that means I've got 2" of insulation blanket and will have, say 5-6 cm additional of perlcrete. It may be on the low end as for insulation, but I'm also limited by space on the oven stand.

There is a bit of bounce/space between the chicken wire and the insulation wool in places, I guess that will be filled with perlcrete later on.

I did get a big bag of Japanese glassfiber wool for free from a friend - the stuff used to insulate walls. Initially I thought about adding it, but it's really soft and spongy and I don't really know how far it will tolerate heat and water (from the perlcrete) so I think I won't use it after all.

[Yokosuka dweller]

Found an air breather to allow pressure to escape the dome insulation. For the pipe fitting, I had to resort to a piece of PVC pipe since I couldn't find a proper fitting that worked with the size. I heated up the pvc pipe and it screw in very tight. It seems sturdy enough, and drilling some holes to allow steam/air to find it's way.

Now I have to just figure out how I position it in the v/p-crete so that it stays solid later on. Maybe some screws or wire through the breathing holes to create anchors.

[Gulf]

It is better to anchor the vent into the stucco/render or outer brick layer. Skip the down tube with the holes and just leave a void (a hole from the blanket layer) up through the "v/p-crete". Fill that hole with scrap blanket insulation. Here is a link to a recent thread about anchoring a bushing/vent. It also has some other links with pics.

[Yokosuka dweller]

Thanks Gulf, and for providing links to clear images that illustrate what you're explaining. I hadn't considered to just leave a void/channel filled with insblanket or perlite, but that seems to ensure that the apex remains insulated as much as possible while keeping an air channel. Very good. And yeah, I may scrap the pvc tube idea if I can find a nut that's the correct size and then tighten some lash/chicken wire in between a couple of washers at the right distance.

As for brick or stucco finish. I had not read up much on that yet. I was going to go with just stucco since I've got a lot of hydraulic lime and cement left. But the brick look is of course superior (imo). I have a whole lot of old red house bricks laying around in the garden. I guess I could clean them up and cut slices to place in the stucco to emulate the brick design, is that the right way to do it? And as for water/weather resistance: Even I am planning a simple single pitch roof structure to protect the oven from the worst, it will get some weather impact. Such 'normal' house bricks seem pretty porous - what's the consensus on weather proofing them, or maybe I can't use that option after all?

Thanks!

Simon

[Gulf]

Simon,

I don't know about a consensus for weatherproofing (sealing brick and stucco). I'm a little out there all by my self sometimes with my ideas toward that. If you research it the consensus has been that brick and stucco need to be slightly porous in order to keep moisture from being trapped. I agree with that to the extent of the use to which brick and stucco are normally used. That use is for exterior vertical walls. Not for a roofing material. On an igloo style oven, stucco has been hijacked for the oven exterior because of it's ease of installation.Some exterionr dome brick also. That is where the vent idea comes into play. It along with elevating the floor insulation, providing weep holes, and waterproofing the exterior of the dome should combine for a dry floor and dome imo. The roof that you plan to build over the oven shouild always be considered the first line of defense against water intrusion. While designing the roof over, think about projectiing it out over the entry enough for you to work the oven while remaing dry.

All that said, I'm all for sealing or waterproofing the exterior shell of an igloo style oven.

[Yokosuka dweller]

Thank you Gulf for sharing your thinking on the stucco/breather logic. I am planning for a roof to extend beyond the immediate face of the oven, and potentially with an extra extension roof held by heavy duty folding brackets, which can be closed of a massive rain is expected - or something along those lines. I really love your build and particularly the roof arrangement, but I can't have the same footprint, nor do I have the skill to do that in a nice way.

I wanted to find out based on your photos from your build but there are a few details I couldn't glean. I hope you could share. Let me make it as brief as possible.

1. The bottom 'course' of your p-crete insulation outside the insulation blanket - it looks like you started with a normal layer of mortar/homebrew. Is that correct? Was that to have a firm base or to insulate against water intrusion?

2. As for final payer of brick splits, I can't see from your build thread clearly. So the splits are half brick size (6,5x11,4x11,4cm/4.5x4.5x2.5"), as they would be in the normal internal fire brick layer is it? How thick were the splits? Can I get away with doing 1/1,5cm (about 1/2") splits? Did you just do a scratch coat with notched trowed on top of the stucco layer and then pressed the splits into the fresh tile mortar then? Once that was set, did you put anything on top of the bricks to increase water resistance of that? I've got a bunch of old red house bricks but also a large amount of very weathered/partly faulty but cool looking fire bricks and many splits from the build itself, do you think those fire bricks would work as splits, if coated with smth afterwards? If so, what would I coat with? Im not sure if cobblerdave is still active in this forum, but I know he also used brick splits, so maybe he'd also know what to do in this case...

Thanks for any inputs on this kind of finish.

[Gulf]

Hi Simon,

I want to apologize again for my choice of an outside photo sharing site for my build thread.

One of the "brain farts" that I had was to build my stand too small for a 44" oven. The firebrick set firmly on the stand. But, 3" of blanket and 3-4" of vcrete plus the stucco and brick veneer would protrude a little on the sides and back. After thinking about it I poured a reinforced cantilevered concrete ring on top of the concrete hearth. I designed it to work also as a guide for a rotating form to guage the vcrete layer to true up the shape of the dome.

My splits were approximately 7.75" X 3.5" X .5". They are brick flooring splits. A local shop cut them from "Old Chicago" brick. The floor installers want the smooth cuts. So, the first cut and the remainder from the last cut were discards. Those are what I wanted for my build. I cut those slts into 3 equal slices. I rotated them and cut them to fit. The upper rows were beveled to compensate for the upside down V much like what many of us do for laying the firebrick dome. I used an interior/exterior grade thin set mortar to apply them to the dome. On most courses, I spread the thinset on to the dome with a knotched trowel. In some cases, I buttered the back of the brick with the thinset. I used flooring spacers to keep the mortar joints uniform.

I did not do the normal layers for stucco. Though, I think that they woud work just fine for this purpose. I was going for a very tough shell, similar to ferocrete. You may want to do a search on it to understand the principle. That meant spacing a mesh (hardware cloth) away from the vecrete to solidly embed the reinforcement wire in the stucco. I used a normal stucco mix, but replaced some of the water with acrylic fortifier. I painted a coat of the fortifier onthe out side of each layer before applying the next. My stucco/ferocrete shell is about 3/4" thick. With the acrylic additives, it is about as waterproof as you can get. Waterproofing the brick and grout outside of that did not seem important.

I hope that this helps. If not, I may be able to organize some some pics and explain further.

[Yokosuka dweller]

Thank you Gulf, this is really helpful. I will investigate more the option for a final brick split finish. I've got a bag of alkali resistant nylon fibres, so might be able to use that to do something similar to the ferrocement option you describe if I can find some local acrylic addition to it.

Meanwhile we've definitely got spring on the door step. I've planted some starter seeds of different varieties of tomato, paprika, and herbs in a makeshift growing box outside. Excited to see them come.

Chimney and anchor plate also arrived - no dents in the chimney at all...I had feared that could happen. I used JRPizza 's way to drill through brick for bolting anchor plate to flue with stainless steel bolts. Seemed a cheaper option than wedge anchors which are quire expensive and hard to find the right size around here. Used father in law's drill press to get through the bricks straight. Worked well. Also used Utahbeehiver's and Gulf's way to make a guiding template/arm for the next step which is a 5cm layer of p-crete on the insulation blanket. Tomorrow my nephews are coming to visit, since schools are still closed around here. Need to find some work for them in the garden.

[JRPizza]

Did you cut slots in the tops of your bolts or make other provisions to prevent them from rotating? Don't remember if I needed to hold the bolts as I tightened the nuts but figured it was cheap insurance vs having to deal with a "spinner"

[Yokosuka dweller]

Did you cut slots in the tops of your bolts or make other provisions to prevent them from rotating? Don't remember if I needed to hold the bolts as I tightened the nuts but figured it was cheap insurance vs having to deal with a "spinner"

Hi JR, yes I did cut slots in the bolts - great method to control the bolt from the top, which if you had not shared I wouldn't have though of. Mortared the bolt bricks yesterday and had to pull them apart and re-do to ensure the bolts actually come up where the anchor plate holes are - a bit tricky. Am leaving it to cure for a few days before tightening the anchor plate. I think the bolts will be mortared in pretty snug by then, so should be relatively doable to tighten the nuts.

[JRPizza]

The slots were a trick I learned from work I had to elongate a few of the holes in my anchor plate, but figured it is mostly a tension joint so tight holes aren't necessary. I would not have needed to do so except I free hand drilled my holes and had a bit of angle/wander so the bolts did not end up exactly where I wanted them to be. I should have used my drill press like you did!

[Chach]

Looking real good!

[Yokosuka dweller]

Looking real good!

Thanks Chach, although it's nothing compared to your whole outdoor area. Definitely something I aspire to do as extended project, if budget, wife (and time) allows. I also been looking at your (and others' ) build for info and inspiration on how to make a curved roof structure to protect the oven. I really like what you've done on oven enclosure. But I will probably leave the oven 'open' and just have a roofed pergola type of structure to protect against the worst downpours. Curved roof beams could be done in steel but I don't know how to weld, so that's not an option. Can also be cut in solid wood, as long as you don't curve the cut so much so you run across grains. You used fat ply, isnt it? That's definitely an option, but like with glu-lam probably I can't do that given I'd keep the beams open to a degree of weather impact. So, still mulling over this one...