I have always wanted to have a wood fired oven at home , I just love the way they make food taste! I am a BBQ addict and the wood fired oven was the next step for me , unfortunately I didnt have €1000 plus to buy a lovely kit to make my oven. I decided eventually that I shouldnt let this stop me so I started Googling and eventually built my own oven. This blog post is a quick description of how I made mine – it doesnt mean that it is the correct way to do it , its just my learnings!
How you build the base will depend very much on where you are building your oven. I was lucky that my back garden is higher than my bbq area so all i had to do was knock a few blocks out of a wall and then begin my base in the garden. If you need to build your base from the ground up there are a wide variety of ways to do this , I have seen timber sleepers , concrete blocks and metal frames all built to support your main pizza oven. Just remember that you want your finished pizza oven at a nice height to work with so that you can easily see in to monitor your fire and cooking.
How big you need to build the base depends on how large your oven is going to be. In theory you only need the firebrick layer to extend just beyond the internal size of your oven , but I made the base big enough to hold the whole oven (approx 120cm x 120cm)
My first step for my base was to add a layer of biggish stones on top of the earth layer. I added these to try and stop the base of the oven getting too damp but also to add to the thermal mass of the base so that it would soak up lots of heat and cook properly. On top of the stones I added a layer of sand ,this was mainly done to add a nice stable and flat base for my fire bricks.
The cooking surface on the base of my oven is made from fire bricks which I saved from some old storage heaters. I didnt do anything fancy with these other than lay then as flat as I could. I used some premixed fire cement as grout between the fire bricks so that I would have a nice smooth surface to cook on, I didnt want my pizza peel catching everytime I slid it into the oven!
As you will see in the below images one layer of my fire bricks was at a bit of an angle , this was because I discovered that the foundations of the nearby wall stopped me digging down. In the end this didnt matter as it only supported the outer walls of the oven rather than being my main cooking surface.
The main structure of your pizza oven is built around a form. There are a number of ways of building this form – I used the sand form method , which had pros and cons! The pros for the sand form method is that it is quick and easy to constuct , the main con is that you have to dig out all of the and from the inside of your oven which is a pain! You can also make your form out of timber which might be worth looking into ! There is also the gym ball technique where you build your oven over a semi inflated gym ball , again I didnt try this but its worth looking into depending on what size you want your oven to be.
My sand form was made of approx 150 – 200kgs of builders sand. Its as simple as building a pizza oven shaped pile of sand! Just remember that this form will be size and shape of the inside of your finished pizza oven , so you need to leave enough space around the outside for your insulation and finish layers! When I was building my form I also included my entrance / door section in the shape , you can add this after if you want but I thought it was easiest to build it all together! It is important to put a bit of thought into your form as your build it ( I didnt!). Make sure your oven is high enough to allow you build a decent fire. Your oven must be big enough for you to light a fire and have room to cook your pizza(s) – mine could probably squash 2 pizzas in but practically speaking it works best for 1 pizza at a time (this isnt an issue as the pizzas only take 90 seconds to cook!)
As you will see im my pictures my door section is quite small , if I was building it again I would build it a bit higher to allow me to add timber and clean out the fire more easily. You could also build the door section square to allow you to easily add metal door to your build.
The Thermal Layer
Im calling this layer the Thermal Layer – Im not sure what the correct name for it is but its basically the inside layer of your pizza oven , and the one which has to withstand the most heat , but also store this heat so that it can radiate it back to cook your food!
I did a bit of reading online about the number of different ways to make this layer – as with all the decisions that I made in relation to my oven I decided what to use based on what I could get for free or cheaply!! I was lucky enough to chat to two local potters who kindly gave me some of their old waste potters clay. Some of this clay was old and dried up and some was still soft. For my thermal layer I decided to use the dried up clay, mostly out of lazyness as I thought that this was the easier option!
There seemed to be a wide variation online about what ratio of clay to sand mixture to use , some people saying 1 : 2 (clay to sand) and some people saying up to 1 : 4 or 5 . I went with 1 clay to 3 sand by volume. Basically for each batch of mix I made I used one bucket of smashed up dried clay powder to 3 buckets of sand. In the end I used approx 25 kgs of clay to 75 kgs sand (maybe a little less) . If you dont have a friendly local potter stay tuned and I will give you some other suggestions!
To build the first layer of the oven I mixed the “batches” of clay and sand dry first and then slowly added water until it come together. The mixure should form into a ball that deforms when you drop it but doesnt completely squash. I covered by sand form with some newspaper (to make it easier to get the sand out later) and covered it completely with the clay/sand mixture. I used a small builders trowel and my hands to spread the layer as evenly as possible. Try and make sure that this layer is as well stuck together as you can at this stage – any small gaps at this stage are likely to crack as your oven dries. I made this layer approx 2 inches thick – I have no idea how thick it should actually be! I think that if I was making my oven again I would build my thermal layer thicker – perhaps 2 layers of 2 inches, allowing the first layer to dry before adding another layer. The more of this layer that you have the more heat that your oven will store in it – allowing you to get to higher temperatures but also to make amazing slow cooked overnight roast dishes etc.
Once I had this layer built I allowed it to dry for 2 days – these days were nice sunny Irish days . I did cover my oven with a tarp at night to try and stop it getting damp. As the layer dried some cracks did appear. I used some of the fire cement that I had left over from building the base to fill in these cracks – you could also just mix up a bit more of the sand and clay mixture and use that .
Once I thought my thermal layer was dry enough I carefully started to dig out all of the sand form from the inside of the oven. This came out quite easily as the newspaper layer stopped the sand from sticking to the clay mixture. Once the sand is out you can now see the size of the inside of your oven – I wont lie it was quite exciting to see the oven start to take shape! At this stage you could leave the oven for another day or two if you wanted to allow it to dry slowly from the inside . I didnt have the patience for this so I lit a small fire in the oven to slowly build the heat in the oven and start to bake the clay.
I quickly discovered that without a chimney your oven just will not work – there is so circulation of air so the fire gets no oxygen and quickly smothers itself. At this stage I got a decent knife out and burrowed a hole into my oven to act as a chimney – I made this hole just where the main pizza oven meets the door/entrance bit. I could probably have put the chimney a bit further up the main oven dome to allow for better circulation. I didnt really have a plan for my chimney at the time so I stuck a bit of old pipe on top of the hole as a temporary chimney and that seemed to work just fine for the initial firing of the oven. Your chimney has to be at least as tall as the highest point at the centre of your oven.
Key to the correct working of your wood fired oven is the insulation layer(s). These layers stop all the heat from your thermal layer being wasted into the air – you want to keep all of that heat in! For my insulator I used a product called Vermiculite – you can find this in any hardware shop – I think its about €25 for a huge bag. Vermiculite is a fireproof insulator that works really well for this layer. I have read that you can use sawdust or straw in this layer as insulators also – I decided to splash out on the Vermiculite as I wanted to ensure the oven was well insulated.
For this layer I had run out of my dried clay so I swapped over to the normal potters clay. You can use this technique for the first layer too if you havent gotten some free dried clay like me. You can buy potters clay from pottery suppliers and that will give you a great product to work with. (dbipottery.com was recommended to me – €75 euro for 100kg)
To use the clay I cut it up into small pieces (about the size of a deck of cards) and left it soak in some water. Use as little water as possible here as you dont want your finished product to be too watery. After a few hours I got my hands dirty and started smushing up the clay with the water to create a clay slurry of sorts. Once all of the clay was dissolved I mixed in my sand and vermiculite. I didnt add as much sand to this layer – not sure on ratios here but honestly I dont think it overly matters! If you do use Vermiculite try not to squash it too much when you as creating your mixture as you want to keep as much air in the mix as possible to keep it as insulated as possible. I applied this layer in the same way as the first layer.
I added the chimney at this stage too. I was lucky enough to find a perfect aluminium tube that works perfectly as my chimney. I think a good metal drainpipe would work well – or I have seen people just build the chimney out of the clay mixture too (you could do this around a plastic pipe as a form and just slide it out when the clay is hard). I built up the insulation layer around the base of the chimney to support it.
I waited for this layer to dry for a day and again lit a small fire in the oven to help it dry out.
I decided that I wanted some more insulation so I added a second layer which was almost exactly the same as my first insulation layer. I did add some cement to this layer to make it a bit harder and to assist with the oven being a bit more weatherproof.
I decided not to build a roof over my pizza oven so I decided to try and weatherproof it. How this will go longer term I have no idea – I will update this blog if needed!
For my final layer I used a sand and cement mixture – I just used normal cement , maybe you would get less cracking with fire cement. To make this stick better and to reinforce the whole thing I added a layer of chicken wire around then oven. I paid a bit attention to trying to make this layer look a bit prettier as it was my outside layer – I took a bit more time making the shape look better and giving it a rub of the trowl at the end to try and smooth it off a bit.
Again I left this layer dry for a day or two before lighting a fire. Some cracks did form but again I just filled these with a bit more fire cement.
The First Pizza
There is a bit of a knack to using a wood fired pizza oven , I am lucky enough to have worked with one before so had made all of the cooking mistakes before.
Wood fired ovens take a while to heat up – its not like a BBQ where you light the coals and 20 minutes later you can cook. The pizza oven really needs to heat up both the floor of the oven and the thermal layer of the top of the oven. To correctly cook pizzas you need to have a good balance between these two sources of heat – you can get the air temp in the oven very hot quite quickly but if the base of the oven hasnt heated enough you will end up with raw pizza base and burnt toppings. I have started heating my oven for about 3 hours before use. Im using standard timber logs that I buy in small bags – I havent gotten around to playing around with different types of timber etc yet – but I will. Dont be tempted to put any timber offcuts that have paint / varnish or are treated into your oven. Also I think that timber with alot of sap in it such as evergreens isnt good for the ovens (or the food!).
I tend to start my fire slowly to let the heat build up in the oven , gradually moving to a nice roaring fire! I build it in the centre of the oven initially to get lots of heat into the floor of the oven. When I am getting ready to cook I push the fire to the back of the oven – I just made a t shaped pole kind of thing to do this – Im sure there are proper tools out there!
I use a deck scrub with very hard bristles to give the cooking area in the middle of the oven a bit of a brush before I use it just to try and get rid of some of the ashes which you dont want on the bottom of your pizza.
Youll want to get a metal pizza peel – you can get these in loads of places online.
I am going to get a thermometer to check the oven but from past experience I think that it is probably getting up to 400c + . My pizzas are taking 90 seconds to cook and coming out delicious and crispy. I recommend turning your pizza during the cooking too as the side closest to the fire will usually cook a bit quicker.
I use Jamie Olivers pizza dough recipe but play around as see what you like. The same goes for sauce and toppings – Im not getting into that debate!
I hope this is of some use – it is just my experience – I have no idea if it is correct or not but it seems to work and it makes delicious pizzas!
250 approx of builders sand
80kg approx of clay
1 bag of Vermiculilte
1 bag of cement
25 fire bricks from storage heater
1 small bucket of pre mixed fire cement
Chimney – whatever you can get your hands on that will withstand the heat