Concrete board as outer structure over Casa Oven?

[nikko]

Ok, I'm new here but think I have the part about building a hearth down. I'm looking at getting a Casa 90 or 110 oven. I want to finish it with a square "superstructure", that that has a hip style roof that terminates at the chimney. If I build a Durock cement board box around the casa, and fill the space with vermiculite and finish the durock with stucco, would this be a good/effective insulator, and would it be durable?

A picture of my idea is here:
Picasa Web Albums - nikko - Pizza Oven

[dmun]

Re: Concrete board as outer structure over Casa Oven?

That should work fine, although for the sake of simplicity you may want to take your flue straight up from the vent, rather than tilt it back to the center of the hip roof.

Speaking of hip roofs, some of our members have found the construction of hip roofs chalenging. A simple peaked shape with gables may save you some hair pulling.

And yes, loose vermiculite fill should work fine, as long as you have a minimum of four inches between the exterior of the oven and the inner edge of the concrete board. It has a tendency to leak out from surprisingly small cracks, so you want it pretty well sealed.

I'm not a stucco guy, but I think that stucco on the roof will be subject to water staining. You may want to think about another roof treatment like slates or tiles.

And why does the sketch-up guy wear a tee shirt over a long sleeve shirt?

[james]

Re: Concrete board as outer structure over Casa Oven?

Nikko,

I think you have it right. In fact, I like your idea so much, that's how I did my oven. :-)

[gjbingham]

Re: Concrete board as outer structure over Casa Oven?

Geeze, dmun cracked a joke! I knew it was in there somewhere!

The man wears a t-shirt because he has no eyes and can't see that the fashion is outdated.

[asudavew]

Re: Concrete board as outer structure over Casa Oven?

And why does the sketch-up guy wear a tee shirt over a long sleeve shirt?

Cuz he has fashion sense that we don't have.

[RTflorida]

Re: Concrete board as outer structure over Casa Oven?

Those are the Gucci line of WFO extra long gloveless gloves

[RTflorida]

Re: Concrete board as outer structure over Casa Oven?

Somebody add an eye or sunglasses to this guy, kind of creepy having a truly blank stare on his face.

[nikko]

Re: Concrete board as outer structure over Casa Oven?

That should work fine, although for the sake of simplicity you may want to take your flue straight up from the vent, rather than tilt it back to the center of the hip roof.

Yeah, I tried to depict that in my drawing, but my 3d modeling skills are lacking. I planned on the hip to be more sloped from the back to front, and the front being near vertical.

Speaking of hip roofs, some of our members have found the construction of hip roofs chalenging. A simple peaked shape with gables may save you some hair pulling.

Yeah, good point. I'm also liking the gabled "cabin style" ovens I've seen. I may make a cabin, but still use cement board instead of plywood/osb.

And yes, loose vermiculite fill should work fine, as long as you have a minimum of four inches between the exterior of the oven and the inner edge of the concrete board. It has a tendency to leak out from surprisingly small cracks, so you want it pretty well sealed.

The red silicone fire sealant was what I was planning on the inside joints.

I'm not a stucco guy, but I think that stucco on the roof will be subject to water staining. You may want to think about another roof treatment like slates or tiles.

Another good point. Slates would look nice.

And why does the sketch-up guy wear a tee shirt over a long sleeve shirt?

Google = Hipsters!

[DrakeRemoray]

Re: Concrete board as outer structure over Casa Oven?

I did a similar finish (but with a flat roof). Note that I used an insulating blanket and loose vermiculite.




Hope that helps.

[Barberque boy]

Re: Concrete board as outer structure over Casa Oven?

As long as the subject came up about moving the chimney flue to the center of the oven. I have some conflicts with my WFO I am to the hearth stage right now. It was my intent to use the simpson double flue with the 30* angles to kick the chimney back to clear some timber framing,and the eves. The front of the oven sits under a patio. But when I went to the simpson graphs to calc out the depth to height ratio the roof line would be extremely high before the flue would straighten out to go up. So I am considering rolling the flue over top of the oven according to some pictures I've seen in an sometimes referred to site.

MHA News - 2006 Meeting - Backyard Oven with Peter Moore

I believe its the 2006 MHA annual gathering and about 2/3-3/4 of the way down they show this style of flue that would allow me to keep a lower profile on my oven. I hope this was the appropriate place to ask this...thanks

[jengineer]

Re: Concrete board as outer structure over Casa Oven?

You can get excellent tips and techniques by looking through the MHA web site. Take a look at their transition from the oven to the throat of the vent area - CHAMFERED. This has been discussed previously on this board. It helps to turn the flow. One thing to remember is that the ovens made during the annual meeting are torn down after they are used - so no insulation. One thing I like about the reverse flow or squirrel tail set up for the chimney is that you have extremely hot gases flowing over the dome radiating heat back into the structure. I would heavily insulate the horizontal section.

If you do this you would be the first one on this site to do it. That means lots of pictures please.

[dmun]

Re: Concrete board as outer structure over Casa Oven?

I think the squirrel tail oven is an unproved idea. The flue gases may help to heat the dome top (which is the hot part anyway) but they will certainly help cool it down in retained heat cooking.

All this becomes moot if you have to run your project past a building inspector. A 30 degree bend is the max allowed by building code: it's the biggest angle you can get a flue cleaning brush past.

Can your reposition your oven entry so it's closer to where the flue needs to end up?

[Barberque boy]

Re: Concrete board as outer structure over Casa Oven?

This will probably be the path I go down unless some body here has some really bad feedback. I figure the top of the dome will help heat the flue for draft. But there's that 30 degree angle rule, although the dome dose roll nicely. Yes I would like to imitate their(MHA) throat and venting. My chimney will probably end up going ten feet to meet roof line tolerances. I would transition to S/S once I could go straight up......thanks

[Barberque boy]

Re: Concrete board as outer structure over Casa Oven?

Dmun sorry I over lapped you, I don't think there's any room to move the entry. I hadn't thought about the ovens ability to cool quicker also. There wont be any building inspectors, I've kept it unattached, but still do not want to violate any basic principles that would cause future problems. What do you think about doubling the fire brick on the underside of the flue where it travel over top the dome. this could accomplish two things. insulate the dome and change the angle of the flue. I had also thought of taking clay flue liners and laying them over at an angle instead of the bricks the MHA showed . ...thanks

[james]

Re: Concrete board as outer structure over Casa Oven?

You can use two sets of Simpson Duravent 30? (and still meet code and the installation instructions), to get a steeper angle -- which will make your hipped roof lower (a sharper angle) and it might help you get the chimney where you want it.
James