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cuda 05-23-2008 06:57 PM

Dome Brick Orientation
Hello all,
I've been lurking and researching here for awhile and am getting ready to start my oven. However, I want to run my plan past others to make sure I'm on the right path.

Since I will almost certainly have no need to bake bread for three days or cook large turkeys, etc., I want to make this thing a little thinner so it heats up relatively quickly and stays hot enough for great pizza, which is the main reason I'm building it. I absolutely want to bake loaves of bread, but probably only a half dozen or less at a time (per firing, not all at once).

Given these parameters, I was wondering if placing the bricks on the flat side with the long axis of the brick following the horizontal circumference of the dome would be okay. That would mean the dome's brick thickness would be 4.5". The dome would not be quite as spherical, but a little more polygonal, I suppose. This has very likely been addressed on this board, but I just haven't found it yet. Any issues with doing it this way?

This would result in fewer bricks laid and less cutting, but a thinner dome, if I've understood how they are usually laid. Given my lack of interest in the oven staying hot for days, I wonder if this is a good idea.

On top of my reinforced concrete base, I was going to pour 4 in. of vermiculite/portland and then the floor. I'm still not clear, however, on floor material to use. I would think that the floor is the most critical part of the oven and would have the greatest influence over the outcome of the crust. It appears that some use firebrick and others use soapstone. I guess I still don't know what material is best for nice pizza crust. Could someone advise me what the concensus is? In the meantime, I suppose I'll research more. Thanks much in advance.

Ken524 05-23-2008 07:27 PM

Re: Dome Brick Orientation
Hi Cuda, Welcome!

We've had a few folks build ovens with bricks "on the side" similar to what you describe. The most "famous" one that comes to mind is Dmun's Geodesic Dome (it's sort of in a class by itself):

From what I've read, Dmun is very happy with his oven performance.


Originally Posted by cuda (Post 33222)
It appears that some use firebrick and others use soapstone.

The vast majority of us used firebrick. I like having the floor and dome made of the same material so they heat and cool at the same rates.

CajunKnight 05-23-2008 09:01 PM

Re: Dome Brick Orientation
Check out this thread and download the plans to have a look.

A 4 1/2" wall on the dome is right on track. The plans call for the bricks to be cut it half. Look it over and see where you stand. BTW welcome to the forum.

gjbingham 05-23-2008 10:13 PM

Re: Dome Brick Orientation
The only problem I see with your plan is that as you build upwards into the dome, the mortart gaps become larger and larger between successive courses, in relation to the layer below. Cutting the bricks in half reduces the gaps underneath the course you're building.

Look at some interior dome shots on the photos. You'll see that the mortar joints develop V shapes that become larger and larger as you get closer to the top. More mortar, less brick. A longer brick will increase the height of that V significantly, at least that's what I'm thinking.

As you get to around the 7th course or so, I'm guessing that the mass of a single brick is too great for the mortar to hold it in place. That leads you to relying on a form to lean the bricks on, in order to keep them in place. After that, you'll be cutting bricks anyway, as the length of the bricks will be so great in relation to the circumfrence of the circle that you'll be unable to get more than just a few bricks per course before you can't make the turns.

Cutting bricks is easy but boring work. I recommend it for your pennance.

Frances 05-24-2008 03:20 AM

Re: Dome Brick Orientation
There's also that graphic which shows that a thicker dome is more stable... where was it again?

Here we go, check out these links. But then again, dmun's thinner dome worked out well...

Auroville Earth Institute is a research, design and developing agency for vaulted structures, construction of various Vaults, Arches, Domes (VAD).

dmun 05-24-2008 05:08 AM

Re: Dome Brick Orientation
Bricks- Standard duty firebrick is easy to cut on a diamond saw. There's no reason to build a jaggy dome from whole bricks on the theory that bricks are hard to cut. And yes, 4.5 inches is the standard thickness for domes. I built a dome with bricks on their edge for a 2.5 inch thickness, but every brick had to be cut to fit in a geodesic pattern. It's neat to look at, and I'm glad I did it, but it may not have a high labor-to-results ratio. There's a structural reason for a dome that thick, and I don't think you want to vary much from that plan unless you want to live adventurously.

The only soapstone floor I ever heard of was in a demonstration oven built at the Masonry Heater Association gathering. I can't vouch for it's performance or stability.

So, speaking of soapstone and geodesic ovens, I am noodling around the MHA site looking for the picture I linked to above, and look what's right on their front page: a soapstone geodesic oven!

Is that cool or what? It's the first time i've EVER had manufactured oven envy.

cuda 05-24-2008 05:10 AM

Re: Dome Brick Orientation
I know that as I reach the upper courses I will have to cut the bricks to get better results with the gap and fitment, but I thought maybe i could save some cutting on the lower ones. I'm not trying to take shortcuts, but if good results can be obtained with less cutting, I'm willing to look into it. If not, then I'll cut the bricks from the beginning.

How much gap is permissible at the outside surface of the dome? If the inside faces are tightly fitting with minimal exposed mortar, which would presumably keep any mortar from falling into the food/oven, how critical is it to have perfectly tapered bricks with small joints on the outside of the dome?

Thank you all so much for the quick replies and the warm welcome. This board seems like a nice place to be.

biondoli 06-02-2008 12:58 PM

Re: Dome Brick Orientation
it looks like you need to review your evaluation of what you will be saving if you do the project as you described.
If you are also willing to cut bricks on top of the dome, so then why don't you cut all of them? it is not difficult, it is not very labor consuming when you compare it with the rest of the project, so why don't do in the right way?
The issues and head aches you are asking with your plan are bigger that what you might think.

gjbingham 06-02-2008 10:23 PM

Re: Dome Brick Orientation
In addition to Carlo's comments, you must consider what mortar you will be using. The larger the mortar spaces between bricks on the outside results in a loss of heat retaining ability of the oven. While I'm not familiar with the specs on Refmix, it may be the only mortar that approximates the refractory properties of firebrick. Others will not hold heat nor reflect it back towards the cooking area. The larger the gaps, the more inefficient the oven, at least in my little mind.

I did a pretty standard build using bricks cut in half. I only have heat enough to do one good bake of bread as the temps fall after the pizza's done. I can easily do six loaves, but that is all at once. Once the oven's down to 425, its time to plan for pasta or beef. Larger mortar gaps, I believe, will cause your oven to cool even quicker. I've only got a half-hour to 45 minute window from 575 down to 450ish.

While I believe that you could still do everything you plan on at this point with your plans, you must ask yourself if you might possibly want to trying to do some other type of cooking with it later that requires more efficiency. Its your oven and your palate. You must decide what you want and build it for yourself.

SpringJim 06-03-2008 04:42 AM

Re: Dome Brick Orientation
There's also been discussion of cutting the bricks in three for a thin dome pizza oven. Has anyone actually done that?

would be a little thicker than Dmum's but less than the 1/2 brick standard.

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