First step was a 100mm thick concrete pad (approx 1.5 x 1.5m) to take the base.

I’m not a fan of concrete blocks (they remind me of public toilets) so I made an ‘H’-frame (same height and width as the concrete blocks) out of scrap timber and built up the base layer by layer. The frame was screwed together so I could undo the outer boards to remove the frame once the concrete had set. Angle fillets were nailed into the corners to soften the edges and assist removal between courses. After having trouble removing the formwork from the first layer, I shortened the inner legs of the frame (by approx 5mm) to create a slight taper to enable it to slide out and release more easily. Worked well from then on.

The key is to ensure the timber H-frame is level before pouring each course.

As you can see in the photo, I used scraps of timber to support the ‘H’-form as we moved up each layer. It was surprisingly easy.

Concrete blocks would be easier but I like the rustic look of off-form concrete. We chose not to vibrate the concrete to ensure we left plenty of rustic air-pockets at the surface.

Once the 5 layers were completed, we poured a 100mm thick slab on top, complete with mesh and 10mm reinforcing rods.

I made sure this slab was completely level to ensure we had a true surface to lay the hearth on.

It was also a chance to iron out the inconsistencies that crept in as I was placing the concrete base layers.

You can’t see it from the photo but the back of the oven also has the same opening for storage – created by using the ‘H’-frame.

First thing to note in this photo is the tinfoil water-proofing film on top of the concrete slab.

Managed to scramble enough old firebricks from around our property to complete the brick base – a great lesson to never throw anything away!

As per the ‘Shed’ plans, these bricks were simply placed dry on a 5-10mm layer of sand. I spent considerable time ensuring the bricks were completely level with no edges sticking up – each brick was checked with a level (both ways) as this will ultimately support the cooking hearth tiles.

A haunch of plaster around the outside is all that stops the bricks from moving at this stage.

My helper, Gracie was getting bored at this stage.

A line drawn from each corner gave me the centre of the brick base. I then made up a pair of callipers from scrap timber (nail in the end of each leg and a small tightening bolt at the pivot point) to scribe the dome circle.
Note the break in the circle for the door opening. All as per the ‘Shed’ plans.

I laid the special pizza shelf tiles on a thin bed of sand/cement mortar inside the first layer of dome bricks to provide the final cooking surface. Again, I took great care to ensure this was completely flat. You wouldn’t want this cooking surface to be uneven or have ridges that catch every time you are placing or removing food items. I used a masonry disc on a small angle grinder to cut the pizza tiles. Before cutting the pizza tiles, I used paper and scissors to cut templates for the outer tiles. Once I was happy they fit OK, I transferred them to the tiles, traced around the outside, then cut the tiles.

This archway initially gave me problems. The day after placing the first archway, when I tried to remove the formwork I found that it was jammed in place and I cracked the mortar trying to get it out – bugger!

Solution – cut about 10mm off the flat base of the ply archway support then prop it up on thin 10mm thick fillets of scrap timber. When you want to remove the archway frame, simply slide out the fillets so that the arch drops down clear of the bricks and comes out easily.

I also chose to remove the archway formwork while the mortar was still wet. I figured any slight movement in the plaster would then have a chance to ‘heal’. As a further precaution, I supported each end of the archway with 3 loose bricks whose weight stopped any tendency for the lowest brick at each end to move (see ‘Dome Construction Underway’ photo below). Job done.

Looks ugly as hell but nobody sees it so don’t worry.

The Inner Arch & Setting Up the Dome Plywood Template.

A few things to note here:-

I wanted to use the earth plaster mix recommended in the 2^nd ‘Shed’ plans but I got impatient and decided just to go with standard sand/cement mortar (8:1).

Despite the fact that both our house and winery are built from earth (the house from our own site) I did not have any dry clay on site and I did not fancy using puggy wet clay.

Also, it was going to cost more in freight than the clay itself to ship this from Auckland.

Hopefully the sand/cement will suffice – guess if the bricks drop from the top of the dome in a few months I’ll know I made a bad call.

Secondly, you can see the plywood template I used to define the shape of the dome. I wasn’t careful enough placing this as I worked my way up through the courses – I don’t think it was fitting snuggly for some of the (half) bricks. As a result, I had a significant variation in height between the two sides of the door opening when I got to the top layers. This caused a few issues that required some ugly mortar work to fix. Another ‘bugger’ moment – fortunately not one that can be noticed in the finished oven (the outer plaster layers can hide a multitude of sins).

You’ll see I’ve changed from the whitish fire bricks to red bricks in the 3rd^d course of the dome. No reason for this other than I ran out of fire bricks. Ideally, I guess firebricks for the whole oven is best as they have greater heat-retention properties. The ‘Shed’ plans suggest plain red bricks are OK for the dome – this is good because they’re much cheaper than firebricks if you have to buy them.

A ‘bad hat day’ here!

You can see the loose brick supports for the inner arch in this photo.