Saint Helena Oven

[dmun]

I was planning on boxing it at the roofline, but giving it 2" of clearance. Can't really think of a good way to support it without the bracing transferring heat to the metal unless I use something like insulation blanket.

I'm going to infill the space around my oven outlet with insulating concrete. I do plan to use a thin blanket, but just to allow for expansion, I have lots of room for insulation. The insulation will keep the heat away from your structure. You can pile vermiculite concrete up inside chicken wire, and make an enclosure for your flue. I wouldn't plan on supporting it directly with your metal studs. Do you know that full length masonry chimneys have the flue tiles stacked up inside a half-inch-on-every-side cavity, and are unsupported until they get to the chimney caps? Strong stuff.

[Marcel]

Double ridge beam is the BEST house frame improvement

<snip>

My father had the brilliant idea of not having a single ridge beam, but two beams - one on either side of the chimney. We further decided to tilt these beams to the angle of the roof so that we didn't have to cut birds mouths into the stringers that went on top of them. We theorized that cutting a notch into these metal studs robs them of a lot of their strength. Plus, it's harder! <snip>

.

(M) IMHO the double ridge beam is the single most important contribution to the framing of the oven enclosure I have seen. Kudos to you and your dad. The solution is a perfect example of "thinking outside the box". I wish I had thought of it before I curved my flue to avoid the ridge beam.

(M) I had posted a caveat a day or two ago during the time that there was some FornoBravo Forum complications and I guess you hadn't had a chance to read it prior to putting your roof up. It was the suggestion to clad your walls FIRST and only then put on the roof. That order would make attaching the top of the cladding under the eaves much easier. You would then put up your roof exactly as you did.

(M) I decided against flue tiles all the way up as their weight was over 125 pounds. But your framing is so much stronger than mine that I think you'll be fine.

(M) I had considered notching my top flue tile to accomodate the ridge beam but several forum builders discouraged me from that because of the hot smoke weakening the ridge beam. I have photographs of that as well as my solution of using single wall flue pipe and elbows to "S" around the ridge beam and place the chimney to one side of the ridge beam. The metal flue pipe was much lighter than clay tile. I wrapped it in chicken wire and then insulated it with Perlcrete.



(M) If you want to see more of my less than elegant solution go to:

http://s14.photobucket.com/albums/a318/marceld/

Ciao,

Marcel

[jahysea]

It's looking good. The flue tile isn't that heavy, in relation to what it's sitting on. The arch should be plenty strong to support a few pieces of flue tile sitting on top of it. It's a good thing that your structure is made of metal, so you don't have to worry about clearance to combustibles.

Thanks David. I thought the metal studs would still need a tiny bit of clearance? Those flue tiles will get 3-400 degrees? The metal studs would eventually lose all strength exposed to that temp? If that's not the case, then I'd like to build a box tightly surrounding the chimney right at the roofline to provide lateral support for it.

I was planning on boxing it at the roofline, but giving it 2" of clearance. Can't really think of a good way to support it without the bracing transferring heat to the metal unless I use something like insulation blanket.

[dmun]

It's looking good. The flue tile isn't that heavy, in relation to what it's sitting on. The arch should be plenty strong to support a few pieces of flue tile sitting on top of it. It's a good thing that your structure is made of metal, so you don't have to worry about clearance to combustibles.

[CanuckJim]

Buttress

Jahysea,

The buttress work shows you have the right idea to prevent spreading, but I'd go one course higher and fill the gap between the dome and the buttress bricks with brick wedges and mortar. Can't be too careful, particularly when you'll be adding the weight of the flue.

Jim

[jwnorris]

Wonderful job. Great detail photos. This will give several of us ideas to move forward with.

[jahysea]

Issue - Chimney

I have flue tiles to stack for the chimney.

But the walls needed to be built right above the edge of the slot in the arches that will feed the chimney. I decided to go ahead with the walls and figure out the chimney tomorrow.

The pics below kinda demonstrate what I'm talking about, taken from above looking down.

I want to give at least 1/2 inch clearance between that metal tray and the chimney tile.

Method 1: Notch out about 1/2 of the tray. In the second picture I drew the cutout in red and simulated the flue tile in blue. Not that this tray already has a horizontal support in the front, revisited in the third pic. I will be adding a similar support just above the top of the arch, to support the concrete board I'm screwing to the front of the oven. I could easily add yet a third one of those if I felt it warranted.

Method 2. As previously mentioned, I plan to cut an arc in the bottom of the first flue tile to meet up with the top of the arch. I could make the arc at the back side deeper than the front, to tilt the flue tile slightly backward, enough to give clearance to the metal tray above. I'd then have to cut the top of the flue tile to get it back to level so that the rest of the chimney goes straight up.

I'm leaning heavily toward Method 1. DMun's already mentioned how hard the flue tile is to cut. And I don't like the heavy flue tiles #2 and upward resting on an initial tile that is at an angle.

Any other thoughts are welcome, although I'm thinking I'll tackle this in the AM.

[jahysea]

Roof Part II

Because there is no ridge beam, we had to get creative in making the stringers meet at the ridge. It turned out very solid, the first two pictures show them in place.

The third and fourth pics show a beam ready to be snipped. I used tin snips for the whole project btw. In retrospect I wish I'd dug out my chop saw and put on the abrasive blade I bought for it. I could only have done the clean cuts with it, anything with tabs would have needed to be snipped, but it still would have saved my hands some wear and tear.

The last pic is the end of the day.. Sense of accomplishment!

Roof still not done, need stringers at the front and back. I plan for the lower supports to be the studs I run along the ends of the other stringers. If I don't like the stablity I'll add more bracing, but I suspect it will be fine.

[jahysea]

Roof stringers

My father helped me out today, and we were brainstorming how to box the ridge beam around the not yet built chimney.

I'd shown him the excellent pictures pointed out elsewhere in this forum:

http://new.photos.yahoo.com/colonelcorn76#page1

My father had the brilliant idea of not having a single ridge beam, but two beams - one on either side of the chimney. We further decided to tilt these beams to the angle of the roof so that we didn't have to cut birds mouths into the stringers that went on top of them. We theorized that cutting a notch into these metal studs robs them of a lot of their strength. Plus, it's harder!

The first pic below details how we braced upward for one of the ridge beams.

The second gives you a visual of the two ridge beams splayed outward.

Third pic, we screwed the stringers right down to the walls, no birds mouth cutout there either.

The last two pics show some detail of the support for the beams. The beams are two sticks of metal screwed together.

[jahysea]

Building walls

You can see from the butress pic's above and these here that I finished the metal walls around the sides today. I've added a little detail in this post.

The first pic is of a brace put in sideways to help bear the weight of the roof above the arch. The second pic shows how the brace was tabbed for screwing in.

The third pic shows how I stair stepped over the concrete I poured to raise the hearth in front. I poured it around the front of the oven, so I had to step over it.

[jahysea]

Buttresses

I rebuilt the front arch this morning, and installed buttresses.

Used a few brick scraps where the tunnel walls were irregular and stacked 3 bricks on either side. Should keep the arch from spreading.

Important as I'm going to place the weight of the clay flue tiles onto the arch bricks.

[jahysea]

First Pizza's

I know there is a different Forum for food, but I can't resist. We made some Pizza's snacks early in the day yesterday (Thanksgiving). Turned out well. Not the first food I've cooked in the oven, as we made some steaks with one of the latter curing fires.

My wife makes fantastic Pizza dough, everything turned out well. The first one was plain cheese pizza, as anyone with young kids would well know!

Pizza's number 2 and 3 got eaten before I could take pictures, but I've attached one of pizza number 4.

[maver]

Not having seen the materials yet, but knowing the sections are only 1' in length, how do they join together? Are they fluted to overlap each other I wonder, or are they straight and I will just mortar them together? If the latter, I suspect they will need additional support, which I can provide as they go through the roof.

They come in both fluted and stacked. Most of the time flu tile is lined on the outside with a brick surround with about 1/2" air gap - this insultation helps the flu tile get hot which helps it draw better.

You are correct in pointing out the force on the outside of the arch walls. Big cathedrals in Europe like the one in Lincoln England have giant extensions with piles of masonry outside along the walls (not sure of the architectural term) to keep the weight of the roof from pushing the wall outward and over.

A buttress is a solid support as you are describing. A flying buttress "flies" - there is an air space below the post that buttresses the wall. Given the thermal expansion issues this might not be appropriate for an oven.

I could easily make a little brick wall on either side of the arch tunnel walls. If I placed it on top of the concrete I just poured I'd be pretty confident they will never move. And nobody would ever see them as they will be inside the walls.

This is what I did. Because it was not visible, I used rubble - left overs from dome construction mortared in place. I was paranoid, so I also placed an angle iron across the front arch and supported it on either side of my rubble to provide additional support.

[Marcel]

Be sure to clad your walls BEFORE you add your roof!

I also started the metal walls today. <snip>
Weather and family fun permitting I should be able to finish all 4 walls and possibly the stringers for the roofing over the long weekend.

I plan to stucco the exterior and use spanish tile on the roof, to match our home.

(M) I made the mistake of framing the entire oven enclosure, including the roof joists and collar ties BEFORE I clad the walls. BIG MISTAKE. I really had trouble screwing the "HardiPlank" s under the eaves because of the pitch.

(M) Cladding your walls before you add your roof, IMHO, will also add significant diagonal bracing and will make the roof easier to work on.

Ciao,

Marcel

[Marcel]

Flying butress

[QUOTE=jahysea]

"You are correct in pointing out the force on the outside of the arch walls. Big cathedrals in Europe like the one in Lincoln England have giant extensions with piles of masonry outside along the walls (not sure of the architectural term) to keep the weight of the roof from pushing the wall outward and over."

(M) Perhaps the term is a "flying buttress" (I'm not sure of the spelling)
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