Brisbane Build

[Hatzi]

Decide for the next few courses i would not cut my bricks down any further, as there would be a lot of wastage. So instead I would use the offcuts from previous brick to fill the gaps in between the whole bricks ( as can be seen in pic 2 and 3). This turned out better than what I expected.

Getting close to plugging the dome - not far now!

[Hatzi]

School holidays - got to love them!!!

Continuing the dome build.

The obligatory head inside dome photo - probably working on the plug or cleaning the mortar from the inside.

The dome is finally done. Must admit my 13 year old son provided lots of help for the last 2 courses and the plug.

I let the mortar dry for a day or so and then started the first low temp fire which ran for a bout 5 hours.

[Hatzi]

At this point I need to turn my attention to the landing and the vent.

I have decided that I will not use a flared landing.

This is where I need help please (have already mailed utahbeehiver and oasiscdm)

I think that I will be using a double layered flue, with an internal diameter of 200mm. My reasoning for this is that it is a bit safer as the external flue will not get as hot.

I am not sure what size the vent opening should be nor the landing.

I am wanting my vent to be similar to oasiscdm's as seen in his posts 600, 629, 633

Waiting for approval from oasiscdm to post his reponse to my questions. However would love to hear other peoples ideas.

[david s]

A double flue is really only required if the flue penetrates a roof. The pipe is usually well out of the way to pose dangers of burning. You will get a shock when you total the cost of the double flue system. You can save a fair bit by having an outer 250mm pipe made up in colour bond and stuffing around 300 mm between the two pipes at the base with blanket.

[david s]

Generally any brick wall should not have it’s brick widths any thinner than 100 mm. (Yours are 75mm) This is because there is insufficient strength in a narrow brick joint. Because of the extra stress created by the thermal cycling, particularly during the early fires to drive out the water when temperature and thermal expansion differences are extreme. You could parge the outside of the dome with 25 mm homebrew to help redress this issue. What do other builders think?

[Hatzi]

david s I will be getting my dad to make the flue - should not cost me anything. Hopefully

[david s]

Whoa, slow down. It is generally considered that a min of a week drying is required before applying any fire. Not only does the mortar require damp curing to enhance its strength (not sure what mortar type you used), but the slow elimination of moisture from the oven is essential. To reduce the extreme temperature differential between the inner and outer brick surfaces it is also considered prudent to do the drying fires after insulating the dome rather than before.

[oasiscdm]

HI Guys

I agree David

There are posts I think in Cobbler Daves build where he and I discussed drying of ovens. hey David you might remember it ,I cant find it. I don't think it was in my thread. We discussed tempering an oven which is what I did over a 6 week period on the first build. Not sure if it made a difference or not will never know but after 3 years of use before I moved there was not a single crack. and trust me my son once had a fire we measured at 530c and I wasn't happy about that as I had to wait for the bloody thing to cool down to cook pizza. LOL oh that was outside brick temperature from my installed thermocouples, Internal thermo was higher than that.

[oasiscdm]

Am Waiting for approval from oasiscdm to post his response to my questions. However would love to hear other peoples ideas.

Hey hatzi

No need to wait for approval just post the answers.

My answers were about the flared landing which you aren't doing now, My bad, I should read more closely. if you look at my posts you will see how I cut the circle in a single tile. took forever from memory.

[Hatzi]

So not much has happened since my last post - in fact i have done nothing!

Need to buy more bricks for the entry arches an the the chimney.

However am also planning to finalize the dome - so i am after some advice.
I am tossing up between the following:
Cover the brick dome in the following order

1.

• perlite (not sure of thickness to make this worthwhile)
• insulation blancket
• concrete render (not sure of thickness to stop cracking of render)

2.

• insulation blanket
• concrete render (not sure of thickness to stop cracking of render)

Any advice on option 1 or 2 and thicknesses would be greatly appreciated.

[Chris inPA]

If you already have the blanket, do this order:

1. Thermal blanket
2. Perlite/Portland cement mixture at 8:1
3. Allow to sit for a week and then start your curing cycles.
4. After the cycles are finished then the cement layer.

[david s]

Can I add
5. Cover the cement rendered layer to hold moisture in it to enhance its strength. For a week
6. Allow to dry for a week before firing.
7. Cook a few roasts for a few firings (chooks are fantastic) before racing straight to pizza temperature.
8. Treat the exterior with a waterproofing layer of the oven is exposed to the weather.

[mongota]

So not much has happened since my last post - in fact i have done nothing!

Need to buy more bricks for the entry arches an the the chimney.

...i am after some advice.
I am tossing up between the following:
Cover the brick dome in the following order

2.

• insulation blanket
• concrete render (not sure of thickness to stop cracking of render)

Any advice on option 1 or 2 and thicknesses would be greatly appreciated.

I did the second choice, insulation blanket with concrete render over it.
I covered my dome with four layers of 1" thick ceramic fiber blanket insulation. My goal was singe-fire, several day cooking, thus the four inches.
I covered that with expanded diamond mesh or stucco lath.
I then added two layers of a portland cement stucco-type of mix, the first coat worked in to the lath, the second coat a few days later to build up thickness. If that was to be my final surface, I would have done a third coat. But since I was covering my dome with a stone veneer, I only did two coats. Final thickness of the shell after the two coats was maybe 1/2"-5/8".
For waterproofing, I then used a product called Thoroseal. It's portland cement based. Mix it up, apply with a thick brush. My first coat was uncolored (white), I added some carbon black colorant so the second coat was a gray color. Thoroseal is waterproof, but vapor permeable. So any interior moisture can be driven out through the insulation, through the render, and pass through the Thoroseal in to the atmosphere.

[MarkJerling]

Weekend 3:

Some more research as i was working on the cooking floor and the plan changed slightly.

Decided to lay the refec tiles on top of hebel bricks.

I like your build. I've also used Hebel (but in large panel form, 75mm thick) as the base of my oven.

[Hatzi]

I like your build. I've also used Hebel (but in large panel form, 75mm thick) as the base of my oven.

I saw someone in South Australia use them. Once i did some research about the properties of Hebel bricks, it made sense to use them.