1&2. The base should finish at an optimum height of 104cm including the 150mm concrete slab. It can be brick, block, steel table etc.. There is no definitive way of building the base, as long as it can support the weight. It is usual to use the space underneath for log storage. In this example, the building is on a raised garden area, which therefore reduces the amount of brickwork needed. You must build your oven from a solid foundation. In this case, it was a 100mm concrete slab, but a well established or solid patio base, such as 60mm thick flags laid on concrete, should take the weight. Internal construction needs a structural engineer to confirm floor capability for weight bearing.
3. In this example, we built pillars to support concrete lintels, which support the blocks (old flags work just as well) which in turn will hold our concrete slab in place.
4. Here you see concrete lintels and block and how much weight they can support.
5&6. Continue with lintels and blocks until you have a complete base in which to pour concrete. It is critical that NO steel is used in the construction of the slab. Steel rods in the lintels are OK to use, as they are 210mm from the surface and not part of the slab. It is also critical that no timber or flammable material is used in the construction of either the slab or the oven housing.
Keep timber a minimum distance of 150mm away from any hot surface, or line it with a suitable insulator.
6. Pour and level the concrete.
7. The more level the concrete slab at this stage the easier it will be to lay the floor of the oven at a later stage.
Assembling the Oven
1. Always position the arch first and roughly lay down the floor to make sure it fits and you know exactly where you want it to finish. Mark where the arch and floor should be and remove the pieces.
2. Start again with arch in the position you have marked. Make sure to rub off any rough edges with a masonry rubbing stone. This rubbing process applies to all of the pieces; the ovens are hand made in moulds and will have rough edges or protrusions which will stop them fitting neatly together unless rubbed down.
3. Lay the floor as flat as possible. You are looking to avoid any ‘lips’ where your pizza paddle can get caught up. If the concrete slab is good, the floor should lay flat. Rub over the joints with the masonry rubbing stone to get the joints as flat and smooth as possible. Only if necessary, use ‘spots’ of the refractory mortar to pack up low points. Do not stick the floor down as it is designed to be able to remove and replace pieces through the mouth of the oven should any become badly worn or cracked over time.
4-9. Working slowly put the pieces of the oven together. When all pieces are together, wiggle each piece from underneath with a small crowbar as necessary to achieve ‘best fit’. The pieces are hand made so don’t worry if they do not go perfectly together. The most important thing is to get the inside joints as smooth as possible (pic 8) , the outside joints are not important. Do not worry if there is a small gap between the floor and the finished dome as this is normal (pic 9). Please note that our oven here has 4 pieces; yours may not have the same number.
10. Paste over the joints with the refractory mortar. Do NOT pack the mortar into the joints. You are creating a seal, rather than cementing the pieces together. Your oven is a refractory product, which will heat up and cool down, so the pieces need to be able to ‘move’. You will see in our installation that we have used a damaged piece. This shows that it does not matter if a piece is cracked, as long as it is not broken.
11. Also mortar around the perimeter of the oven.
Building the Enclosure
1-3. Build your enclosure. In our example, we have created a design using exterior grade plywood, which has been painted with a heavily textured paint, to give the impression it has been rendered. We have used clay roof tiles and a clay chimney pot from a reclamation yard.
4&5. Create a gasket with the insulation blanket and fix the flue manifold in position on top of the arch using raw bolts. If your oven has the concrete manifold, it should be fixed in position using the refractory mortar. If using the metal manifold, drill very slowly using a masonry drill bit. DO NOT use a hammer action, as this may damage the arch.
6&7. Cover your oven with the insulation blanket. Use all of the blanket and cut and mould it to shape where necessary. The more layers the better.
8&9. Fill the remaining space in your enclosure with V4 vermiculite crystals.
10. Make sure your enclosure is watertight – it is not essential for the enclosure to be airtight and, in fact, it is best to have some air flow through the enclosure.
11. Stand back and admire your work and prepare to enjoy your oven for years to come!