Pompeii oven in Switzerland

[Frances]

...or at least there's going to be if I have my way. Though as a busy mother of three it might take a while.

I've only just started. We poured the foundation last Saturday and have the bricks arriving to make the stand today. I've been reading the forum a lot recently, but there are still some questions I didn't find an answer to:

- Why does the foundation have to be bigger that the stand and hearth? I'd like to put down patio slabs around the oven on a bed of gravel, and don't really want the concrete sticking out at the bottom.

- The bricks I have for the stand are quite large (over 2o kg each, that is erm... about 50 pounds) and we've used them before for a dry stone wall. Could I get away with building the walls of the stand as dry stone walls, or would it be better to stick them together with mortar?

- would it be possible to insulate the dome just with insulfrax, and then cover it directly with a layer of chicken wire and cement (and weatherproof stucco and mosaics and whatever)? I'm not sure I'll be able to find either Vermiculite or Perlite around here.

- And finally, here is my firebrick question: If the firebricks have the right alumina content and the right weight, does this mean I've got the right bricks? Things here all have different names and it's really difficult to work out what exactly I'm looking for. Plus all the experts (i.e. professional oven builders etc) keep telling me I need other products, which usually cost three times as much.

This website is so cool, can't wait to get started on the dome!
All the best from Switzerland,
Frances

[jwnorris]

Re: Pompeii oven in Switzerland

<snip>
- would it be possible to insulate the dome just with insulfrax, and then cover it directly with a layer of chicken wire and cement (and weatherproof stucco and mosaics and whatever)? I'm not sure I'll be able to find either Vermiculite or Perlite around here.
<snip>

This is the way I built mine. I ultimately used four 1" layers of the blanket below the chicken wire & stucco. I did it because of a space issue.

I works wonderfully.

J W

[dmun]

Re: Pompeii oven in Switzerland

- Why does the foundation have to be bigger that the stand and hearth? I'd like to put down patio slabs around the oven on a bed of gravel, and don't really want the concrete sticking out at the bottom.

In order to support whatever decorative covering you put over your oven. More after your next question

- The bricks I have for the stand are quite large (over 2o kg each, that is erm... about 50 pounds) and we've used them before for a dry stone wall. Could I get away with building the walls of the stand as dry stone walls, or would it be better to stick them together with mortar?

In the States, the oven stand is made of concrete blocks. These have huge cavities which are filled with rebar and concrete, when they are dry stacked. If your bricks have big holes in them that will support a column of concrete then you can dry stack. If not, better mortar. These concrete blocks are as ugly as homemade sin. Your bricks may be attractive enough for your final finish. If so, then your base slab doesn't have to overhang, but you need a plan for the exposed edge of the oven slab, which is not attractive to look at.

- And finally, here is my firebrick question: If the firebricks have the right alumina content and the right weight, does this mean I've got the right bricks? Things here all have different names and it's really difficult to work out what exactly I'm looking for. Plus all the experts (i.e. professional oven builders etc) keep telling me I need other products, which usually cost three times as much.

Yes, if the alumina content and weight is fine, your bricks are fine.

Please post your progress, and the names of stuff and suppliers you use. This will help us help other euro-builders

[Hendo]

Re: Pompeii oven in Switzerland

Hi Frances and welcome!

If the firebricks have the right alumina content and the right weight, does this mean I've got the right bricks? Things here all have different names and it's really difficult to work out what exactly I'm looking for. Plus all the experts (i.e. professional oven builders etc) keep telling me I need other products, which usually cost three times as much.

Firebricks certainly confused the hell out of me when I started building my oven. The advice from the Forum is to aim for a ‘low duty’ firebrick, which equates in the US to around 30&#37; alumina so I understand.

Here in Australia, I had a manufacturer interstate tell me that ‘low duty’ bricks were 18% alumina, ‘medium duty’ were 26% alumina, and ‘high duty’ were 32-38% alumina. These represent their entire production range, so they were merely expressing the degree of ‘duty’ as an internal identifier.

I ended up getting imported bricks from a local distributor who supplies to all sorts of industries – from bakeries to smelters. In his world a ‘low duty’ firebrick that he sold to bakeries was 40% alumina, and a ‘high duty’ brick was around 80-90% alumina!

So it pays to focus just on the alumina content in my opinion – ‘duty’ classifications are fraught with different interpretations. I can only endorse what dmun says - if the alumina content and weight is fine, your bricks are fine.

The other thing to be aware of is that the dimensions of firebricks can vary somewhat. So when you come to estimate how many bricks you’ll need for your dome, be aware that the ‘Materials List’ in the FB plans refer to bricks which are 2&#189;" x 4&#189;" x 9”. Local ones may well be different, and hence influence quantities required.

Another thing you may want to consider is the question of using tapered bricks vs standard bricks for your dome. I ended up purchasing tapered firebricks, which produce an arch of the desired internal diameter – in my case 1100mm. The bricks are 230mm long x 115mm wide x 76mm high on the outer face and 63mm high on the inside face. These are cut in half to form half-bricks about 113 x 115 x 76/63mm. My choice of tapered bricks was made easy as they cost no more than standard bricks, and they sure make laying easy for a novice – no wedges to prop up each brick!

Good luck with your project.

Paul.

[Frances]

Re: Pompeii oven in Switzerland

Thanks for the answers everyone!

I'll be sure to post my firebrick suppliers later on once I get the bricks. Huh, I'm pretty sure tapered bricks won't cost the same as regular ones in Switzerland though! I'll just have to muddle on through with what I can get - as I'm also an absolute beginner that should be fun.

I'm glad that the the foundation doesn't have to be bigger than the hearth. Of course I went ahead and put the walls right on the foundation edge anyway, but I was worried there might be some structural reason. The real reason never occured to me because my stand walls are out of very beautiful (and increadibly heavy) natural stone blocks, and it would be a sin to cover them up. ... the hearth edge is something I'll deal with when I get that far.

Thanks again for the answers, I'll probably be back with more questions in no time at all.

Frances