Dragan's 900mm brick Pompei oven build. Melbourne Australia

[Gecko245]

I've moved from my original post labelled,Gallery arch and flue query, to post my build progress photos here.

Stage one. Forming up for our 100 mm slab. I used SL81 mesh with some extra 10mm bars along the front and rear curve to give me extra piece of mind. I also used silicone around the edge of the ply to reduce concrete seepage. Six 20 mm weep holes were provided for in middle of the slab.

[Gecko245]

Stage Two. Pouring the slab. I made a small attachment for my multi tool to help vibrate the concrete into position. Initially used a straight edge to level off the concrete about 15 mm higher than the form work which allowed me to tapper it down to the edge as it started to cure. This should help keep water out should it make its way onto the slab. We poured late in the afternoon to help the concrete cure slowly and watered it down occasionally over the next few days.

[Gecko245]

Stage Three. broke up some old tiles and glued them down with spacing to allow any moisture to escape through the weep holes in the slab. I've chosen to use 75 mm Hebel with 40 mm CalSil board ( not installed yet) under the cooking bricks. Cutting and numbering all the base bricks. My theory is that the dome will sit on my base bricks therefore my dome and base will be fully insulated and separate from the slab and the gallery. When i insulate I call install screws in the lower Hebel board to tie of the wire securing the insulation blanket.

[UtahBeehiver]

Great start, thanks for keeping the members posted. As you mentioned, it is really necessary to isolate the dome/floor bricks from the concrete hearth. Any contact would act as a heat sink. Place some window screen material on the bottom side of the weep holes to keep the bugs from making a nest in the weep holes.

[Gecko245]

Thanks for the tip regarding the insect mesh. I had read about it here somewhere earlier but had forgotten to glue it on. This forum has been a great resource for me in both as a research space and direct advice from the members. Whilst I might do things a little different, I plan on following the basic build principles. I'm happy to show my successes and failures for others to learn from. I'm also happy to receive advice if someone sees I'm about to do or have done something questionable.

Now for the part I've been waiting for, building the dome.

[Gecko245]

Just a quick question regarding when I do my final exterior render. Can I use brick sand, as I have some left over, or should I be using a washed sand?

[david s]

Commercial renders/stucco have some waterproofing added to them which which reduces porosity making them partially waterproof. If you make your own be aware that yours wen’t have this quality. The sand they contain is usually finer than brick use sand because the renders are designed to be applied in a couple of thin layers. If you are applying it in between 5-10mm thick, some courser grains won’t matter. The addition of lime in the mix imparts a degree of flexibility in the outer shell as well as some crack self healing properties which I think is an advantage. I also use AR glass fibres for strength, but you can use chicken wire.

[Gecko245]

Thanks David,

I was planning on mixing up Portland cement, lime and brick sand for the base over 3 layers of 25mm blanket covered and tied down with chicken wire. This would be applied at about 30-40mm. I would them apply a final coat of Unitex render, Black which is designed to fade slightly as it ages, as once again I have some left over from previous job and it would tie into the current house colours. My main concern is am I better to get some washed sand or will the brick sand be ok?

I have made a roof over the cooking area should so the oven should be reasonably protected. I have also made the supporting slab in a way so that there will not be much of a lip were the dome sits on it, reducing water ingress at the slab edge.

[UtahBeehiver]

I thought I had posted this but must not of hit enter. Do not render until the oven is cured (with insulation on). Water, when sublimates to steam, volume increases by a factor abt 1500 times with the potential to build enough pressure to crack render. A vent at the apex would be good to install when you do render just in case water gets in later.

[Gecko245]

Hi Utah, thank you for your feedback.

I was planning on curing the oven before rendering but wasn't aware I should have the insulation on for the curing so thank you for that. I never thought of the vent in the render coat but like that idea also. Just need to find something that might suit. I was also considering putting a thermometer in the dome, not so much for pizza cooking but rather when cooking breads and roasts with the door closed.

[Gecko245]

Laying the cooking base bricks.

I've chosen to lay my base bricks to line up with the outer edge of the dome bricks. The edge cuts don't need to so accurate that way. The dome bricks will not be cemented to the floor to allow for any expansion/contraction during use. Laying the bricks in a herringbone pattern for both aesthetics and function, remembering to number them to show each position. I was surprised to find up to 3 mm difference in the brick heights being that they are laid on a 40mm CalSil board. I decided to grind the underside of the high bricks rather than packing up with sand which took me an extra hour. Happy with the floor now as it is has a very smooth and level work surface.

[UtahBeehiver]

These are used a lot and can be found a most auto parts store and cheap (breather vent). Gulf uses wire mesh around a 1/2" pvc bushing to embed in the render. There is a pic some where on his thread.

[david s]

Regarding the outer rendered shell, I think 30-40 mm thick is way overkill, I do mine 10-15mm. Rendering onto the blanket may be problematic due to its springy nature, a firm substrate is preferable. The chickenwire may be enough to make it sufficiently firm. I prefer a layer of 10:1 vermicrete. My problem with the chicken wire over the blanket is that it takes ages to apply over a compound curve and when tightening it compressed the blanket which reduces its insulation value. For chicken wire to act as reinforcing, it needs to be in the middle of the rendered layer. I prefer to reinforce it with fibres. There are many approaches so just go with what you feel.

[Gecko245]

Starting the Dome.
I've just used a bolster to cut the bricks into halves rather than grinding each one. Easier, quicker and less dusty. Light tap to 3 sides and 1 hard tap to break the bricks seemed to work pretty well.
Dome width = 900 mm. Dome height= 515 mm. Door height=330 mm.
I was going to use Home Brew but in the end decided that rather spending time shopping around for the right ingredients it was easier to buy ready made products from a refractory supplier. I've used Airset Tufset Super to fix the bricks into position (up to 6 mm gaps) then filled the external voids with Denscrete 135F.

[Gecko245]

Building the Arch.

I made a form out of some scrap form ply I had to help me with building the dome arch. The bricks protrude from the front about 60 mm which will allow me to insulate the dome around to meet the arch bricks. I also plan to insulate the arch bricks from the gallery bricks with 20 mm Calcium Silicate Board. Initially I had a small angle piece attached to the centre jig but removed it so I could work around the arch. I marked the jig so I would have a reference for the following dome brick courses. I also found the jig would place the next brick course slightly out so this gave me a small amount of flexibility to locate the higher courses in a better position.