Pompeii oven with 1/3 fire bricks - structural issues?

[dariusk]

Re: Pompeii oven with 1/3 fire bricks - structural issues?

Thanks for the encouragement guys. It's a huge motivator to know there is a place to come and ask questions. It makes the prospect of the challenges to come a lot less intimidating. I may set a new record though for asking questions about the bleeding obvious!
This build has been on the cards for close to 10 years now, so no shortage of motivation here. Time is hard to come by, but the plan is to just start and let it take as long as it takes. The hope is for months rather than years though...

Thanks for the link to Bruce's build Dave, I'll have a look through it.

I like the look of your oven Steve, you did a great job! I'm interested in your front arch / flue design. It looks simple but completely effective, which is what I'm after in my build I think. I was looking for top down photo without the chimney to get a better idea how you did. I may ask about this later..!

Wotavidone, I'm feeling very comfortable about the decision to slightly upsize and go with half bricks. While I don't generally mind going a little against the grain, I'm planning on living in this house for at least 20 years or so and it's possible this will be the only oven I build/have.. As this all new to me, I thought too much experimentation may not be a good idea.

I'll start a new build thread soon and keep all my questions and progress together as well

Thanks again everyone, very much appreciated
Darius

[TropicalCoasting]

Re: Pompeii oven with 1/3 fire bricks - structural issues?

Im liking the idea of a thinner dome
Im considering putting the oven on my balcony now(its where we spend all our time and has the views and table and soon to grow grape vine covered roof)
So weight is the problem
Less wood burnt is good too
Shorter heat up time
Less reinforcement of under floor.
Put it on hebel structure to save weight too
Make it a smaller dome.(big enough for my favourite pans)

[wotavidone]

Re: Pompeii oven with 1/3 fire bricks - structural issues?

Thanks for all the replies, very appreciated and has help with this part of the decision making process.
I don't think I'll go down the geodesic dome pathway at this point in time... Interesting read though.
Well, while it's sounding like it's unlikely there would be major concerns with a 1/3 brick dome, I've decided to go with the proven standard half bricks and increasing the internal size slightly to 32" (800mm). Considering my lack of experience with brickwork, concrete and everything else for that matter, I thought the conservative approach would be a better bet.
Lots of reading and planning to do still and lots more questions coming too!

Thanks again
Darius

Good move , Darius.
You'll sleep better by following "convention" and if you are happy to just fill the joints as they get increasingly wider as the dome goes up, you'll cut less brick. Two cuts on 1/3 bricks will only get you 3 bricks to lay, where as two cuts will get you four bricks if you are using half brick.
800 mm is a good size. So far I've built a 750mm, an 850 and a 900.
750 is a little small, 900 is pretty big.

[UtahBeehiver]

Re: Pompeii oven with 1/3 fire bricks - structural issues?

Dariius,

Steve and Dave are right on. Most of us are DYI and like many, I never laid a brick until I started this project. That said, my build was love of labor, labor, labor........ but in you can say you built it yourself. A pretty oven does not cook and better than it's step sister. Like Dave said, if you want inspiration, look at Bruce's build.

[Greenman]

Re: Pompeii oven with 1/3 fire bricks - structural issues?

Hey Darius - If you have the motivation you will produce a perfectly operational oven with the support of the people who have done what you seek to do. Many of us had not laid a brick before we started and have ovens that work fine, most of them look good too.

Do your research, plan well and lean on the crew for what you need help with. There are people who have produced true works of art on the forum who will gladly offer advice. Mine is functional rather than beautiful but I love it anyway!

When you have your planning sorted you will just get the faintest whiff of a pizza and that gets stronger as you progress.

[cobblerdave]

Re: Pompeii oven with 1/3 fire bricks - structural issues?

G'day
Don't consider lack of experience will stop you in any way from producing a full working and beautiful oven.
The minority, absolute minority of ovens in this forum where built by "professionals ".
The rest of them, full on, first timers, worried they " bitten of more than they could chew"
http://www.fornobravo.com/forum/f6/3...tml#post149565
It's even been done out of a wheelchair. Good on ya Bruce!
Plenty of pics lots of questions ..... This bunch will see you through .
Regards dave

[dariusk]

Re: Pompeii oven with 1/3 fire bricks - structural issues?

Thanks for all the replies, very appreciated and has help with this part of the decision making process.
I don't think I'll go down the geodesic dome pathway at this point in time... Interesting read though.
Well, while it's sounding like it's unlikely there would be major concerns with a 1/3 brick dome, I've decided to go with the proven standard half bricks and increasing the internal size slightly to 32" (800mm). Considering my lack of experience with brickwork, concrete and everything else for that matter, I thought the conservative approach would be a better bet.
Lots of reading and planning to do still and lots more questions coming too!

Thanks again
Darius

[deejayoh]

Re: Pompeii oven with 1/3 fire bricks - structural issues?

I think the reason that there aren't more ovens built with 1/3 bricks is because it's more work for less potential performance and minimal cost savings. You have to make more cuts, get less heat mass, and you only save the cost of maybe 30 bricks. To most builders, I am guessing that trade-off isn't worth it.

As you seem to have a specific desire for a thin-walled oven, I say go for it. I don't think you should have any structural concerns.

[david s]

Re: Pompeii oven with 1/3 fire bricks - structural issues?

I followed the geodesic oven thread with great interest. I think the reason the oven cracked was only partly to do with the wall thickness.

I reckon it was also because:
a) the pentagons and hexagons had to be made by glueing smaller bits together, and
b) all the joins between the individual hex and pentagon shapes run full length over the dome.

In the whole dome, the mortar really did have to act as a high strength glue.

In a more conventional dome, each vertical join is ideally only one one course high, then the joint is bridged by a brick.

I do believe there is an potential issue in a thin dome, in that there is less surface area on the faces that make up the joins, but at least the individual bricks can be used to tie the other bricks together somewhat, and the mortar then has somewhat of a gap filling role rather than primarily a gluing role.

totally agree, that's why I cast mine.

[Greenman]

Re: Pompeii oven with 1/3 fire bricks - structural issues?

dmunn's geodesic build is an interesting read. I followed it with great interest. I am sure that there will be a MK 2 somewhere out there with some adventurous soul. The plebs among us will be happy to make a traditional functional MK 1 and dream about how much better/prettier MK 2 will be.

I am interested in a hybrid with the brick dome and cast refractory entry arch. We all need food for though.

[wotavidone]

Re: Pompeii oven with 1/3 fire bricks - structural issues?

I followed the geodesic oven thread with great interest. I think the reason the oven cracked was only partly to do with the wall thickness.

I reckon it was also because:
a) the pentagons and hexagons had to be made by glueing smaller bits together, and
b) all the joins between the individual hex and pentagon shapes run full length over the dome.

In the whole dome, the mortar really did have to act as a high strength glue.

In a more conventional dome, each vertical join is ideally only one one course high, then the joint is bridged by a brick.

I do believe there is an potential issue in a thin dome, in that there is less surface area on the faces that make up the joins, but at least the individual bricks can be used to tie the other bricks together somewhat, and the mortar then has somewhat of a gap filling role rather than primarily a gluing role.

[david s]

Re: Pompeii oven with 1/3 fire bricks - structural issues?

dmunn built his oven using 2 1/4" thick bricks cut into various shapes to form a geodesic dome. His thread is worth reading. He did have problems with cracks in the joins which he put down to the extremely thin (for a brick oven) walls. My ovens have 2" thick walls, but I cast them in three sections using castable reinforced with stainless steel needles, so it can't really be compared to a brick oven. Anyhow check out his build here.

http://www.fornobravo.com/forum/f8/d....html#post3834

[wotavidone]

Re: Pompeii oven with 1/3 fire bricks - structural issues?

I think a lot of the prefab cast WFO's around here have around 50mm dome walls and work reasonably well. 75mm of brick would have to be better/stronger/more versatile??

Hey wotavidone, I appreciate your time with the reply. I'm hoping not to need a reinforced layer around the dome, otherwise I'd likely just use half bricks. I was thinking possibly of a 12mm or so layer of mortar over the dome once done, but not much more and not reinforced. That sounds like good advice to house it in a closed structure for added strength. I kind of like seeing the dome shape though!

Cheers guys

Precast domes probably have quite a bit of thermal mass - that stuff is dense. A 3 inch brick dome would probably not be any stronger though - we are comparing a solid single mass with lots of little blocks stuck together with a less than perfect glue.
Still, that doesn't matter a bit.
IMO opinion a reinforcing layer is not really needed on a 28 inch dome with 3 inch walls, and about all a 12mm mortar layer would do is add a little thermal mass.
If you want the dome shape, you can still achieve all your aims.

It could go like this:

Build a 3 inch thick dome.
Give it a 4 inch layer of (say) 6:1 vermicrete, then render/stucco the outside in your igloo shape with reinforcing in the outer (say) one inch layer.
Then you will have your dome bricks pushing against the vermicrete, with the vermicrete transferring the stress to a reinforced outer shell.
No structural problems at all, I suspect.

All contained - all supported - all good.

BTW, the very lovely Artigiano series of ovens offered by our kind hosts appear to have a wall thickness of just over 3 inches, including a layer or mortar/render. I do lust after these craftsman built ovens.

Brick Oven | Brick Oven Pizza | Outdoor Brick Oven

[UtahBeehiver]

Re: Pompeii oven with 1/3 fire bricks - structural issues?

I believe that DavidS (Aussie) has a thin wall cast oven that is smaller in diameter. He can give you feedback on smaller oven performance and pros and cons.

http://www.fornobravo.com/forum/1528-david-s/

[ATK406]

Re: Pompeii oven with 1/3 fire bricks - structural issues?

After building one, the dome shape really grows on you. Finishing your oven can take as long as the initial build itself and may have just as much influence on longevity too. BTW - Building a thinner wall will work out just fine. You might be raising the stakes just a little bit in terms of "geometric quality", but that is more than offset by your plan to build a smaller oven anyway. In other words, if you were planning to build a thin walled dome with a 2m diameter, you might have issues. I'm really curious how a thin walled oven performs (I suspect that most of aren't saturating our ovens in 2-3 hrs anyway), so I hope that is what you decide to do.