Introduction
Before starting this project, I had no clue about wood fired ovens except the occasional sight of brick ovens in pizzerias and watching some videos about bakers. I had no experience in masonry either.
So obviously, the first thing to do was to try to get the maximum information I could get on the subject. While researching reference material about brick ovens, I found a few websites and forums which were of invaluable help. This helped me to figure out what kind of oven I was going to build and what materials and techniques to use. Among them I have to mention Traditional Oven, the Fornobravo forum, the UK wood fired oven forum to name a few from which I got a lot of information. Reading from people's experience on the subject has been extremely useful.
You can see the list of all resources I read on the resources page.
Clay or brick?
During my investigations, I found about the traditional clay ovens which are made out of clay, sand and straw. These are called cob ovens. The construction consists in shaping a negative of the oven with wet sand and then applying a layer of clay+straw aggregate to form the dome and then removing the sand once it's dry. This has a lot of advantages: ecological, relatively easy to build, easy to repair. However, it's more prone to degradation due to external elements.
You can read about a cob oven build on the Cob oven project and watch a video of the building process.
The other type is made with refractory bricks. This build is more difficult to do but lasts longer and requires less maintenance as it is less likely to deteriorate.You can read about a cob oven build on the Cob oven project and watch a video of the building process.
In my case, since I need to have a stone enclosure to fit with the surrounding, I opted for the brick construction as I felt that I wouldn't be able to do much repairing if the oven started to degrade.
Oven shape
After reading comparisons about the two, it appears that the barrel vault ovens are usually built with thicker walls and retain heat for a much longer time and are generally used by bakers while the domes are usually preferred for baking pizza. But just to contradict this, there's a two meters diameter old dome oven just behind my house which was used to bake bread for the whole village as it is usually the case for all the ovens found in Istria.
Here are some photos of this oven:
But at the end of the day, both can bake excellent breads and pizza and both are good for a private usage.
On the structural aspect, dome ovens are self supporting structures as the bricks are locked to each other due to gravity. Barrel vault ovens on the other hand, need a lot of buttressing to contain lateral forces.
So I kept my initial idea and went ahead with a dome oven. This shape seemed also to be more appropriate in my case given that I wanted to build it in a corner, and be as compact as possible.On the structural aspect, dome ovens are self supporting structures as the bricks are locked to each other due to gravity. Barrel vault ovens on the other hand, need a lot of buttressing to contain lateral forces.
Oven dimensions
The size of the oven was determined by both the space constraints and the typical use I would do. The dome is an ellipsoid (an oblate spheroid exactly) with the following dimensions.
- floor diameter: 92 cm
- dome height: 38 cm (somehow in the end I ended up with 39.5 cm)
- door width: 46 cm
- door height: 25 cm
- chimney section: 25cm x 6 cm
Other dimensions:
- oven hearth: 15 cm of reinforced concrete with steel rebars
- hearth insulation: 15 cm cement + perlite mix ('perlcrete')
- cooking floor: 6 cm of refractory bricks
- dome: 11 cm layer of refractory bricks
- dome insulation layer 1: 10 cm perlcrete
- dome insulation layer 2: 6 cm rockwool + loose perlite + loose leca (light expanded clay aggregate)
3d model
In order to plan the oven properly, I designed a 3d model in Maya (for which you can get a trial version). This was handy to set the proper dimensions based on the space I have in my courtyard. Since I don't have much space, I wanted it to be as less physically intrusive as possible and also to aesthetically blend with the surrounding stone walls.
This also provided me some estimate of the number of bricks I'd need based on the brick size I'd use (22x11x6 cm).
This also provided me some estimate of the number of bricks I'd need based on the brick size I'd use (22x11x6 cm).
In my initial plan, I wanted to taper the bricks all four sides, so that they would fit nicely and form a 'perfect' dome, thus requiring less refractory mortar and resulting in better structural strength (so I thought). Unfortunately, this attempt failed miserably, as I could only taper them along the dome meridians.
 |
| front view - arch entry |
 |
| top view |
 |
| perspective |
 |
| Perspective view, with external walls |
 |
| Global view, including pizzaiolo |
Firebricks calculations
One of the important purchases for the oven are the refractory bricks. You need to properly estimate the number of bricks based on the design you choose. A good idea is to roam around the different forums and see what people have used for similarly sized oven. This should give you a pretty good idea of what is needed. If you have a 3d model, that's even better, you can also do some calculations to get a rough estimate.A rough estimate of the number of firebricks can be simply calculated with the following kindergarten formula:
Num bricks = Area/brick area
I used firebricks in three parts: the oven hearth, the dome and the door arches.
Depending on whether the bricks would be tapered on all four sides or not slightly influences the final count.
In my case, the bricks dimensions are 22x11x6 (units in cm - yes I'm using the ever popular metric system!) and I'm using mostly half bricks (up to the 10th layer), whose section would be 11x6
- oven hearth: Surface = Π* Re2
with Re: external radius = internal radius + brick width = 46cm + 11cm = 57cm
Surface = Π*572 = 10201 cm2
For the hearth, the bricks are laid on their wide surface whose area is 11cm x 22cm = 242cm2. The number of bricks would then be = 10201/242 ≈ 42 full bricks - oven dome:
An ellipsoid surface can be calculated using this ellipsoid area calculator where you provide a=b (dome radius) and c for the dome height
There are two cases: - non tapered bricksThe bricks section fits the interior of the dome and in this case I have a=b=46 cm and c=38, which yields&nb p;for a half ellipsoid ≈ 23562/2 = 11781 cm2 which corresponds to about 11781/(11*6) ≈ 179 half bricks = 90 full bricks
- tapered bricks
Here the bricks section fits the exterior of the dome and a=b=46+11=57
and c=38+11=49, which gives a dome surface of 18533 cm2 which corresponds to 18533/(11*6) ≈ 280 half bricks = 140 full bricks
- The door has an opening of 46 cm (w) x 25 cm (h), and requires two arches made with around 20 firebricks
The total number of bricks is approximately:
non tapered bricks: 42 + 90 + 20 ≈ 150 bricks
tapered bricks: 42 + 140 + 20 ≈ 200 bricks
Firebricks calculator
Now just for fun, here's a firebrick calculator I wrote, just enter your numbers and it will spit out an estimate of the number of bricks you need for the dome + hearth. The actual number will be slightly lower as it doesn't consider the entry area where there are no bricks. But this is slightly compensated by the entry arch bricks (the one supporting the dome) as they are not included in the calculations.This works in any units, as long as you use the same for all dimensions. You can even use parsecs if you like, but that might not be practical.
| Dome radius | Dome height | Brick width | Brick height | Brick depth | Tapered bricks |
| Dome area | Dome bricks | ||||
| Hearth area | Hearth bricks | ||||
| Total area | Total bricks |
(really small smallprint: this is purely indicative and naturally I won't buy you any firebricks if you ordered too much and similarly won't send you any in case you're running short.)