1. What you will need
- A ROCKCOTE Firestone Arch and Door, or something to use a mould for a clay door.
- 23 x 20kg bags ROCKCOTE Clay Cob Base. Or a lot of clay, sand and soil and manure.
- 15 x 17.5kg bags bedding sand
- 2 x bags compressed straw
- 30 x Firebricks
- 1 x adhesive notched trowel
- Shade cloth to mix Clay Cob on.
- Paper template of Base
- A base or stand to build your oven on
- Shelter to keep your oven under
- 450mm long Measuring stick
- Spirit level
- Baby pool, old bath tub, or wheelbarrow
2. Selecting a site for your Pizza Oven
- Firstly keep in mind that the oven needs to be out of direct weather so will need to be built under some sort of structure.
- Check with your local council regulations, in regards to where you can build your oven.
- Check with engineers before building on a patio, or veranda as the oven weighs a substantial amount.
- Also be aware of fire hazards when placing your oven.
3. Enlist some Helpers
With a little bit of help from 4 to 8 friends you can have the majority of your oven built in less than a day. If you want to build your oven by yourself there is no reason why you cant do it gradually over a few days or weekends if you liked.
4. Setting up Site for Building Pizza Oven
Setting up your site properly will make building your oven much easier.
- First separate the materials into Sand, Cob, Bricks, Door and Straw.
- It is easiest to work backwards from where you are going to build your oven.
- Decide on somewhere very close to the oven, about a metre square where you can stock pile completed cobs.
- Set up a sturdy cob building table, ideally somewhere shady about 2 metres away, a tarp might be good.
- Lay down your piece of shade cloth, on the closest flat grassy place.
- Put the two bales of straw next to the shade cloth.
- Put your tub, wheel barrow, or dig a hole next to the shade cloth. And run a hose, so you can mix the cob and water. Put your shovel down here.
- Put your Cob bags, next to the tub, so you can break them into the tub easily.
- You will need to dampen the sand, before you use it to form the mould. Try and do this as close as possible to the oven, as it is quite heavy.
- Put the door and the bricks next to the oven base, you will need them first.
This diagram maps the process from the kit to the oven.
5. Marking where the Pizza Oven will Sit
- Once you have a base to build your oven on trace out where your oven will sit on the base.
- Unfold the paper template from your kit.
- You will need to be careful to ensure your oven is properly centred and square
- The template represents the inside of your oven, i.e. the floor of your oven.
- Find the centre of your oven and align with the centre of the template.
- Ensure that you have the template facing the right way, with the door part at the front. Ensure the front is square with the base.
- Trace around the template with a pencil or permanent marker. This will guide you on where to put the bricks.
6. Mixing up Cob
- To approximately 4 litres of water gradually mix in 1 bag of Cob using a large container like a kids swimming pool, bathtub or wheelbarrow.
- If you are using your own clay click here for more info the correct clay mix
- Continue to stir until there are no dry bits of cob left, adding more water if necessary.
- Spread out the piece of shadecloth on the ground.
- Tip cob mix into a pile on the shadecloth.
- On top of the cob mix place roughly an equal volume of straw.
- Stomp around on the straw and cob until the straw is well covered in cob.
- Roll the shadecloth over to form the cob back into a pile, and continue stomping on it.
- After a few minutes, once the straw is mixed in well, your mix is ready to form into cobs.
7. Forming the Cob into Bricks to Build the Pizza Oven
- To form the cobs, place the cob that was just stomped onto an old table.
- Grab a good handful of clay and start forming it into a rounded brick shape, roughly 20cm long, 10cm high and 10cm wide.
- Knead and roll your cob until it can hold its shape and feels sort of solid.
8. Installing the Firestone Pizza Oven Arch
- Unpack your ROCKCOTE Firestone door arch.
- You can make your arch out of cob, if you dont have an arch, you make you door out of Cob.
- Place the arch at the front of your oven so that it lines up with the line you traced at the front of your oven.
- Ensure firstly that you have the arch facing the right way, so that you can open and close the door.
- Secondly ensure that the arch is square with the front of the pavers and sitting back about 50mm from the front of the base.
- Once you are happy with the positioning, mix up a quarter of a bag of cob mix and a litre of water to make a stiff adhesive glue.
- Move the arch out the way, and with the adhesive trowel, put a line about 50mm wide where you want the arch to sit on the base.
- Place on top of the mortar in the same position you did before.
9. Building the Oven's Walls
- Place cobs around the firebricks.
- Once level with the firebricks, lay more cobs in a radial pattern, placing the inside face of the cobs on the line. (Refer the diagram)
- Continue laying the cobs, packing them into each other firmly, and bringing the walls in gradually with each new layer.
- Smooth the inner walls with water on your hand. It is not necessary to smooth the outer walls as they will be covered over later.
- Don't be shy about pushing a cob wall into a better shape. Ensure that it is leaning in slightly more with each round of cob.
- Build the cob up around the door arch as you go.
- When the walls are 250 to 300 mm high and the arch has been cobbed over, move to the next step.
10. Filling with the Pizza Oven with Sand
- When the walls are approximately 250-300mm high you will to fill up your oven with damp sand.
- Put your sand into a wheelbarrow or other large vessel and wet the sand down.
- Start filling the oven with the sand. Place the measuring stick into the sand and continue filling until the top of the sand is at the height of the stick.
- Mould sand into a ball-like shape as in the pictures and diagrams. This will be the shape of the inside of your oven.
- Once you are happy with the shape of the sand lay some wet newspaper over it.
- Recommence laying the cobs around the oven as before, except now using the sand to support the cobs as you build.
- As you get towards the end, the angle that the cobs are laying at will increase until the last few are sitting almost vertically.
11. Building the Chimney
- To make the chimney, place some cobs around the hole in the top of the door.
- Continue to build the chimney up to above the height of your head when standing. If it is getting difficult to build, you can leave it a few days until the cob underneath dries out and is strong enough to build on top of.
- Leaning the chimney back slightly may help its strength, and to direct smoke away. See figure 1.1
- If necessary you can reinforce the chimney, by building it up with cob behind it.
12. Applying the insulation coat
- Mix up some water and cob into a sloppy paste.
- Dip and roll large handfuls of straw into the mix until the straw is well covered, but is still mostly straw.
- Place the coated straw onto the oven without compacting it too much. Start at the bottom and work your way up the oven.
- If your oven is overhanging the base slightly, stop the insulation coat from sliding down by inserting some sticks into the oven at the bottom of the oven to give the insulation coat something to rest on.
- Apply light clay straw slip as an insulation layer over the inner core.
- If you are looking to do something creative with your oven, this layer can also be used to start to build out the required sculptural elements of the finished design. The layer wants to be kept light and fluffy.
13. Optional Final Coat and Decoration
- The final coat is optional. (Used when you want a smooth looking oven)
- Thoroughly mix together a bag of cob with water to form a fairly stiff paste. (If another colour is desired use ROCKCOTE Clay Decor)
- Spread the mix over the oven using your hands, making it just thick enough to cover well.
- Decorate your oven with old tiles, stones, bottle caps, or anything else you think you would like.
14. Taking the Sand out and Firing
- After about 5 days the oven should have dried out enough to remove the sand through the door arch.
- Once the sand is out you can start lighting a small fire in the oven each day for about a week to help it to dry out.
- After a week of small fires your oven should be ready to start cooking in.
15. Just Do It
- Now you know almost everything you need to know to build your oven. It really is easier than you think.
- The great thing about Cob is that it is very forgiving, you really can't make a mistake that you can't fix easily. The best way to learn is to start doing it!
- If you are planning on Building an oven, let us know and we can give you some more personalised advice.