I have been dreaming about building my own oven for ages now. I started talking about how much I would love to build one when I was renting a two bedroom flat. So I couldn’t really make one then. A couple of years after that we moved to a house, but were still renting and I wasn't going to spend all that effort improving someone else's garden. My girlfriend (Now wife) one Christmas got me all the pizza tools and booked me on the "Build and Bake" course at river cottage. She also got me a copy of "Kiko Denzer - Build Your Own Earth Oven" Which I read cover to cover on the train many times and can’t recommend highly enough. There was no turning back from that point. Finally last year we bought our own house and I could finally build my oven I had been dreaming of all this time!
Step 1: Base
Step 2: Fire Bricks
Step 3: Bottom Insulation
Step 4: Oven Floor
Step 5: Clay
I think we measured took about 13 3 gallon buckets of clay when we finally hit pure stuff. which turned out just enough.
Makeing test bricks is a really good idea. All clay is different (unless you buy it pure I imagine). If you mix up enough clay and sand to make a 1" thick brick shaped lump of clay out of pure clay, 1:1, 1:2, 1:3, 1:4 using more clay. The clay is made up of very fine particals and fills in the gaps between the sand. It stops it shrinking and cracking. Use a ruler and score two lines on the bricks 10" ish apart. When they have dried out naturally (dont rush it) You can see how much the bricks have shrunk and cracked. The mix you choose should be hard and not crumble but not have not shrunk by more than 2% in length.
After making some test bricks I came up with a ratio of about 1-1 sand and clay. I think there was a lot of sand in the clay when it came out of the ground.
p.s. I just went down to the builders yard again for the sand. you need a lot. enough to mix with the clay to make a building mix and make the sand form for the dome. Because clay is made of very fine particales that when mixed with sand, fill in the gaps between the grains of sand. So 1 bucket of clay + 1 bucket of sand does not equal 2 buckets of building mix. Again you will have to trail and error the amounts.
Step 6: Build Day
So after marking out the shape of the oven on the bricks wit marker pen (so you can still see it when wet) I piled up sand in to a form. using a stick 16" in height stuck in the middle of the form. So when you start to bury the stick you know the exact height. Kiko Denzer in his book says it is really important to get the ratio of height to door height right apparently. 16" seams the ideal height which at a ratio of 63% gives a door height of 10". It is all in the Kiko book. Shape the sand into a perfect dome nicely compacted down. Then layer the finished sand form with damp newspaper. This is so when emptying it you can feel where to stop digging the sand out.
Now comes the clay sand mix. No straw like in a traditional cob mix which gives it strength. In an oven straw just leaves gaps and air which you don't want. You want supper compacted clay and sand for thermal mass. To make the mix you spread out a big tarp and cover it with a couple of buckets of sand and in my case a couple of bucket of clay (broken up in to little wallnut sized bits). Then tread it into to each other with your feet. If you have made pastry it is very much like rubbing the fat into the flour. You need to really thoroughly mix them together. A tarp come in really useful to do this as you can turn it all over really easily by pulling one side of the tarp to the other (the bigger the tarp the better). When you think it is all mixed in really well do it a bit more. add a bit of water till it holds together but doesn't splat when dropped from a waist height and you are ready to start building. You are going to do this a lot of times before the day is out. You want to build the first layer all in one go so you dont get and dry joints which will crack under high heat.
Grab a hand full of mix and compact it down into a solid ball in your hand. build it up this way hand full by hand full (4" thick) until you reach the top. My mix was a bit wet and it started to sag slightly. So the higher we got the thicker the bottom got. So by the time I got to the top the bottom was about 7" thick.
Step 7: Dome
Step 8: Drying
Then more drying and waiting... It is SO tempting to light a fire in there and just heat it up and be done with it. Slowly slowly catchy monkey. Just air drying then a few days later couple of tea lights. Then some of those big chunky candles going for hours on end. Then a small fire with kindling. Then next night I tried to do another small fire but it got a bit large and dried it out but some hairline cracks appeared. Next time small fire and decided it looked pretty dry, so cranked it up. I got some cracks about 5 MM on the outside appear but nothing on the inside. Pizzas were good but I don’t think I got it hot enough. and maybe some moister was still in the walls. It took about 5-6 mins to cook a pizza. I am sure I can get that down with more drying and with the insulation layers added.
The final two layers were one of clay slip with sawdust (Nice and loosely packed with loads of air pockets for insulation about 4" thick). When that layer had dried I applied a thin layer of clay, sand and straw mix for plaster (About 1" thick with a very thin coat without the straw to give it a smooth finish).
Step 9: Roof
So I finished this afternoon just in time for winter to hit... oh well couple of weeks the wife and I are hosting a pizza party. So I have got to get the hang of using it before then.
I am no in no way calling myself an expert. I just read a lot about it for a long time before I had a go at it. I hope this helps any of you if you are thinking of doing your own.
If you need any help get yourself over to http://ukwoodfiredovenforum.proboards.com/index.cgi There really is a forum for everything on the internet. There is a wealth of information out there.
p.s. I have full CAD designs for the base and roof if anyone wants them. (I did say I had a lot of time to plan this)
Step 10: Update: Door
I finally decided to bite the bullet and make a proper door for my oven. I have been using the form (see below) that i used to make my arch. but as well as it not looking very pretty there were a lot of gaps for air to pass through. you could feel it pouring out with your hand. after all this effort insulating my oven letting all the heat out makes no sense. I picked up a flue thermometer from Clus Olssen which is an amazing £8.49.
It is all wood and has no real protection. It is only meant as a bake door as I have not chimney so cant fire it with a door on so there will be no flame in the oven when it is being used. So I am not worried about it burning too much.
I glued and doweled together three pieces of 4" x 4" fence post I had left over from building the roof for my oven (best £20 I ever spent on ebay still got enough for a prep table). I cut it large then using a electric planer skimmed off the edges at a slight taper till I got a perfect fit. The handle is also carved out of off-cuts of the fence post.
I added some stove rope in a routed gully just to give it an extra seal.
I kind of like the massive probe. My only worry with this project is that because the first 4" are encased in solid wood so the whole of the probe is not exposed to the full heat. It works really well. I let it get down to normal oven temps and put a kitchen oven thermometer in it and it was bang on the money.
Step 11: Cooking
Step 12: Recipe
Napoletana Pizza Recipe makes 4 10" Pizzas
10g Salt (1 3/4 Tsp) Table salt
3.15g (1 Tsp) instant yeast
450ml cool water
Mix the flour, salt & Yeast together well (making sure that the salt and yeast do not come into contact) add the water all at once and mix to a shaggy ball.
Leave it for 5 minutes for the flour to become fully hydrated and gluten to start to form.
Now knead for 10 minutes or until the dough will pass the windowpane test. (stretch out the dough thinly, it should form a thin skin that will support your finger without ripping)
divide the dough into 4 balls (about 275g each) and place into individual oiled tupperware containers.
leave out for half an hour then put in the fridge overnight.
an hour before baking take them out of the fridge and let come back to room temp. They will have already risen.
1 1/2 tins (400g) crushed Tomatoes / Plum tomatoes drained of most liquid
clove of garlic
1/2 Tsp of red wine vinegar
salt & Pepper
1/2 Tsp Oregano & Basil (fresh if you can get it)
Either lightly blend the sauce with a stick blender or just crush with your hands. there is no need to cook the sauce as the tomato is cooked in the can. the beautiful fresh tomato flavors will be lost if you overcook it.
Topping combinations I really like
Saute some mushrooms with garlic in a frying pan
Fresh Cherry Tomatoes with Artichoke hearts and feta cheese
Olives, Capers & Chilli Flakes