Bricks required for a 43" oven Introductions Discuss Bricks required for a 43" oven in the Good Background Information forums; hi reading thru the articles listed for the quantity of Firebricks needed to build a dome 1meter in diameter (+-42") ...

[brillwills]

hi
reading thru the articles listed for the quantity of Firebricks needed to build a dome 1meter in diameter (+-42") roughly 32 brick in the base course these would be "Snap Headers" (Full brick cut in half)

what im getting at is are the quantity's for full bricks and if so how many does it take to complete the dome , the floor would be around 60 if laid on edge and 50 laid flat ....

Im planning on building 1 in my garden (well ive already started) base being 1.8 m wide and 1.9 long to allow for front hearth , just shuttered cooking hearth ready for 150mm slab , im going to build the dome with firebrick internal skin using a sand cement lime mortar and 25mm foil backed insulation board (kingspan), I want to place a twisted chimney centrally on the dome for a feature but im unsure whether this may allow to much heat to vent too quickly ? and also if the concrete collar i would have to form for this stack to sit on would withstand the heat , I'll post some pix as i go but appreciate any feedback with your experiences in the meantime thanks paul

[Andy]

Hi Brilllwills,
I'm in the uk and just starting to build the beast. I'm not sure what you mean by a central chimney... I think you need an external chimney to make the oven work, with an internal chimney exiting from the top of the dome the bulk of the heat energy will be lost to your oven.

[brillwills]

Hi Andy
Thanks for the reply
I can only think that all will not be lost if i place a heat deflector (metal plate over the hole) to stop the heat from the hearth escaping too quickly through a centraly placed stack , could do a tradtional one but for visual effect a twisted stack would be better

any help or experience would be appreciated

cheeers paul (brillwills)

[dmun]

I want to place a twisted chimney centrally on the dome for a feature but im unsure whether this may allow to much heat to vent too quickly ? and also if the concrete collar i would have to form for this stack to sit on would withstand the heat

You MUST NOT vent the oven from the top of the dome. This has been tried repeatedly and nothing causes more heat losses except a lack of insulation. If you want a central chimney as a decorative feature, you need to have an offset flue from the entry, to the central point. Think about it: would you leave a skylight open in your house all winter? How could you ever stay warm with all the heat exiting straight up?

As to whether a dome will support a massive masonry chimney on top, I would plan on some method of supporting the chimney independent of the dome. The dome expands and contracts with the heat of firing, and has a tendency to crack even when not load bearing. I built a very large chimney on top of my oven, and built a reinforced concrete bridge over the dome to support it. That may be overkill, but I would design your exterior cover to bear the weight of the central chimney.

[dmun]

Two more things:

sand cement lime mortar

This sounds like ordinary masons mortar. It will crumble with heat if you use it to lay up your firebricks. If you want to make your own mortar, look into the fireclay/sand/portland mix recommended here (High Heat Mortar Primer).

25mm foil backed insulation board (kingspan)

Most foil backed insulations are made for domestic use, the foil is a vapor barier, and they are unsuitable for high heat uses. You want a specific insulation used for refractory purposes, or make your own from garden vermiculite and portland cement.

The reason domestic insulation doesn't work is that it contains organic binders that smoke (and stink) in high heat applications.

[dmun]

(from another thread)

thanks for the reply ,
like the look of your project using the triangle technique which should equate to an extremely strong design, Im building mine using a ply rib shutter as a former and plain old half brick laid in a lime mortar backing no internal joints or beds backed off with a 50mm Vermiculite concrete render shaped with a dolly and final face brick course topped of with a twisted stack (Decorative only) im going to rely on convection to vent the smoke out of the front opening , trying to source materials at fair prices here in the Uk is pretty difficult $3 a brick makes for a pretty hefty bill $1100 build cost ! I could buy a Neff Oven for 1/2 that

Lets see? Ply rib shutter as a former? I have no idea what that means. Maybe a sketch or a picture of what you have in mind?

Plain brick (no holes) can make an adequate dome. It's better than no oven at all.

Do i have this right? You're going to build a decorative chimney and then not use it? I'm really scratching my head over that one. Do you want all those hot exhaust gases in your face when your cooking? When you already built a chimney? It's not that hard to build a path from your entry to your central chimney, and it's going to make your oven much more usable.

Just for the record, two inches (50 mm) of vermiculite concrete is about half what you need, at a minimum. You will want four inches, or two inches of the refractory insulation blanket.

[brillwills]

The ply ribs form the template o your dome and are made to sit on a stool supported by a single post the ribs are set at 75mm centres , remove the post at the completion of your dome and you could reuse them to help out a friend when they want a pizza oven!! ? .....hey guys well all need a hand ...and dont forget were building a bit of fun not a "magnox Reactor" appreciate the feedback and will post some pix when i figure out how to ?

PS how do i win the central chimney saga

[gvzepp]

Hi All,

Just joined this forum yesterday and had to smile as already the information here has helped me track down the materials in Australia I haven't been able to do myself for my oven build.
Thanks Carioca i've spoken to Darley Refractories in Bacchus Marsh and they have some of the bits i've been chasing for quite some time now.

Regards:

Brett