John's Barrel/vault build

[JohnR]

I've been collecting materials for six years... And today I began building my wfo. It is a vault with a 36" wide by 45" long floor. The ceiling height will be 19.5 inches with a 11-12" high door. I mortared the first four course today and hope to do the vault (running bond) next week. I have 4" of Calsil under the cooking floor and 2" under the walls. The two boys cleaning bricks in the picture were too young to help when I first started thinking of building a wfo.

First question, more to follow: when transitioning from the ceiling arch to the door arch does is need to be gradual or can it step down (sorry can't think of a better way to describe what I'm asking)?

Second: my entry arch will not be touching the oven door or hearth. There will be a thermal break and I plan on placing the flue on the entry arches. I do not have any more Calsil. Can the entry arch sit directly on the concrete hearth or does it need to have insulation underneath?

All comments and suggestions are welcomed and appreciated.

John

[JohnR]

Re: John's Barrel/vault build

When I began this morning

[JohnR]

Re: John's Barrel/vault build

When I finished

[JohnR]

Re: John's Barrel/vault build

Here are pictures of my progress. I'm getting a nice running bond on the vault. The only thing I am not adhering to is building the end wall underneath the arch... I am wondering if it will do any good to run the last three rows of the arch to the outside edge of the back wall bonding them to the top of the wall rather than the side?

I built the form out of peg board. It was pliable enough to bend and it has the laminate surface so hopefully my messing mortaring won't stick too much.

[david s]

Re: John's Barrel/vault build

Here are pictures of my progress. I'm getting a nice running bond on the vault. The only thing I am not adhering to is building the end wall underneath the arch... I am wondering if it will do any good to run the last three rows of the arch to the outside edge of the back wall bonding them to the top of the wall rather than the side?

I built the form out of peg board. It was pliable enough to bend and it has the laminate surface so hopefully my messing mortaring won't stick too much.

Yes, that would be better than not having it tied in at all. In kiln building a design like yours will tend to have the expanding vault push the end walls out. An oven only goes to about half the temp of a kiln so there is far less expansion, but it is still substantial and measurable so anything you can do to minimise potential problems is prudent. I like your arch, it is far better than a flat arch joined to straight walls, which do produce a lot of sideways thrust. I don't think you'll have any problems unbutressed.

[cobblerdave]

Re: John's Barrel/vault build

G'day john
Like that stand of yours! what's it made of ?
Regards Dave

[JohnR]

Re: John's Barrel/vault build

The stand is some sort of shale/sandstone the pieces are anywhere from 2" to 6" thick. Behind this is concrete block. I was given 2 pallets of the rock years ago and I have been saving it for this (too bad I moved the pile of rock 3 times before it has come to its final resting place.)

John

[JohnR]

Re: John's Barrel/vault build

Today I was able to finish the vault... I am not a brick layer! It is supposed to rain for a couple of days so i have damp towels and plastic over the dome with a space heater inside. Hopefully this helps with curing.

I am using a refractory mortar that suggests 1/16" to 1/8" joints. I have been able to maintain that for the most part because I had arch bricks. The top of the arch is 19.5" from the cooking floor.

As you can see from the picture of the inside the mortar is not coming out of the joint. In many joints it is about 1/8" recessed. Is this ok, or should I be worried about it? The picture of the top shows the mortar in every joint to the surface.

Any other problems/concerns noticed by those who know what they are doing?

Thanks,

John

[cobblerdave]

Re: John's Barrel/vault build

G'day
Building to a form you don't have the advantage of being able to see the other-side of your work. I too built to a form and have recessed joints.
I have a piping bag sitting at home for years now but to date have been too chicken sh$t to crawl into the oven to refinish.
Hasn't hurt the oven at all and it operates just as well.
So it's really not a major worry, repoint the joints if you like, don't and it will not effect much
Regards dave

[JohnR]

Re: John's Barrel/vault build

I am planning on building the doorway this evening/tomorrow. Since I have a vault height of 19.5" I am shooting for a doorway height of 12.3". What about width? Right now my plan is to build an arch (almost semi-circle) that is 24" wide (inside diameter) and 12.3 inches high. My oven is 36" wide so the door would be 2/3's the width of the oven. I plan on using a 13X13 clay flue liner that is 3'-4' high and my entrance area will be 15" deep. The oven is 42" deep so I wanted to have the greatest amount of angle as possible to work the whole oven. (I have long arms!)

Is a 24" wide door a problem as long as I keep the 63% height? Is it unnecessary?

Help... I'd really like to get this done by tomorrow.

Thanks,

John

[vtsteve]

Re: John's Barrel/vault build

That will work. You can close off some of the width with loose bricks (or use a draft door) to limit heat loss while firing, and still have the full width available for loading bread -- or huge pizzas.

[david s]

Re: John's Barrel/vault build

John, your plan sounds fine. I'm a fan of a shallow entry to make the oven easier to work. 15" is pretty deep. You can set the flue tile partly over the oven door to reduce the depth of the entry without creating issues with smoke leaking out the front.

[cobblerdave]

Re: John's Barrel/vault build

G'day
The rule of thumb that the door should be 1/2 the width of the oven is mainly for dome ovens and is just that, a rule if thumb .
Same with the door height. If it were to be 11 ins or 13 ins it wouldn't effect the oven performance in any sort of measurable way.
There is more than one Pompeii oven out there that has had the entrance build before before the dome been complete and " broke " the 63 per cent magic figure.
I'd go for usable if I were you
Regards Dave

[david s]

Re: John's Barrel/vault build

G'day
The rule of thumb that the door should be 1/2 the width of the oven is mainly for dome ovens and is just that, a rule if thumb .
Same with the door height. If it were to be 11 ins or 13 ins it wouldn't effect the oven performance in any sort of measurable way.
There is more than one Pompeii oven out there that has had the entrance build before before the dome been complete and " broke " the 63 per cent magic figure.
I'd go for usable if I were you
Regards Dave

The door of my oven is 74% of the oven diameter. If I were to have designed it 50% it would only be 10.5" wide (ridiculously unusable). The downside is that there's more heat loss out the door. Like wise a really large oven, say 50" diam. with a 25" wide door would be ridiculously and needlessly wide.

In your case John, your oven is deeper than it is wide so you are getting a larger volume. Your plan should be fine.

[JohnR]

Re: John's Barrel/vault build

I did some math today and found out the opening of a semi-circle with a height of 12.5" and a diameter of 24" (ok, almost a semi-cirlce) has an opening of 226 sq. in. Likewise an opening with a 20" wide base and 8.5" walls and an arch that rises to 12.5" at the center has an opening of approx. 221 sq. in. So the semi-circle rounds off the corners and widens the base... seems like a good thing for my situation. I hope to have pictures of the door by days end tomorrow. Thanks for all the advice.