Pizza, bread and roasts from a wood-fired oven – that’s what gourmets love. This unique combination of natural materials and the traditional way of firing gives the prepared food its unique aroma. In order to achieve this, an extremely massive furnace is necessary. Read in this text how to get your own wood or stone oven.
Not of wood but of stone
A wood-fired oven is not an oven made of wood, quite the opposite. Its name comes from the way it is fueled: these massive stoves are fired with wood. However , the wood- fired oven is built exclusively with refractory materials. That’s why this stove is also called a “stone oven”.
A stone oven is a real, small structure that cannot be moved once it has been built. However, it spreads a particularly pleasant atmosphere with its crackling fire, its pleasant scents and its rustic appearance. When installed correctly, it is also weatherproof. A stone oven is therefore an ideal alternative or addition to the barbecue area as a garden object .
Building instructions for the wood-fired oven
A stone oven is a brick building about 1.50 meters high. A building permit is not required for him. In apartment buildings, however, the landlord should be asked for permission before setting up such a fireplace. A lot of manual dexterity is also required.
If this is missing, a corresponding amount of time must be planned. Since the setting and drying times of concrete, plaster and mortar also have to be taken into account, the construction of the stone oven is quite lengthy. All in all, you have to reckon with 3 – 4 weeks until the first bread can be pushed into the combustion chamber.
The construction phases are:
Well planned is half done
A stone oven is a permanent installation . It is also a semi-open fire pit that poses a potential fire hazard. It also emits smoke. The site should take this into account. It must be set up in such a way that it is easily accessible, but neither endangers nor pollutes the house. If this is difficult to implement due to the size of the garden, a correspondingly long flue pipe should be used. This means that the escaping smoke cannot soil the facade.
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Set on solid ground
A finished wood-fired oven can quickly reach a weight of 1-2 tons. Therefore, a particularly solid foundation must be built for the foundation.
For the foundation you need:
- 4 small stakes
- 4 boards, 15 millimeters thick, 2 meters long, 20 cm wide
- ca. 2 m³ Concrete gravel
- that. 10 Sack Cement
- flat shovel
- Mixing tub or mixing machine
- Bitumen sheeting as a moisture barrier
- 2 pieces of steel mesh 1.40 mx 1.40 m
- 30-40 firebricks
A straight square of 1.50 m is marked out with the ruler and the string . The base area is then excavated with a spade to a depth of approx. 20 cm . The bottom is covered with a thin layer of gravel. Above the turf, the floor formwork is made with the boards . The moisture barrier is now laid out so that it reaches the top edge of the foundation formwork. The strips are laid out with a 30-50% overlap .
Now the concrete is mixed in a ratio of 1:4 . When approx. 10 cm of concrete has been poured , the first reinforcement steel mesh is laid. The formwork is filled further and further until the concrete has reached approx. 10 cm below the upper edge of the formwork. Then the second welded wire mesh is inserted. The formwork is completely filled and pulled off just above the top edge.
Once the concreting has started, the work must not be interrupted . The concrete must not harden in layers but must remain homogeneous.
In the case of peaty or loamy subsoil , however, the foundation must be dug much deeper. To achieve freedom from frost, a depth of 80 cm is required. This foundation needs a correspondingly larger amount of concrete. At the latest for this size, a rented mixing machine is strongly recommended in these building instructions.
Instead of gravel and cement, you can also use ready -made concrete in sacks. It’s more convenient, but also much more expensive. The gravel-cement solution costs about 100 Euros for 20 cm flat foundations. For bagged goods , you have to reckon with four times the total for this amount.
After concreting, the foundation is covered and left to harden for 14 days . In hot and dry weather, the foundation is poured with plenty of water 2 – 3 times a day .
The base of a wood-fired oven is also the hearth . The oven door will be around chest height, so the fire needs to be placed underneath to heat the oven cavity. A three-shell construction makes sense for everything that generates heat or stores heat. This reduces the need for fuel . In addition, the outer wall of the wood-fired oven does not heat up as much. This makes the great stove much less dangerous.
The three bowls consist of:
- combustion chamber
- insulating layer
- outer shell
In the inner room the fire is fueled. It must be encased in refractory bricks . Perforated bricks that are bricked up with refractory mortar are reasonably well suited for this. They already provide good insulation , so the insulating layer around them can be thinner.
However, vertically perforated bricks are quite fragile. Fireclay bricks are therefore ideal for building a wood-fired oven . They guarantee maximum heat resistance. However, they are a bit expensive. A chamotte brick in the normal size of 24 x 12 x 12 cm costs about 3.50 Euros. However, only a few stones are required for the combustion chamber.
The size of the combustion chamber depends on personal taste:
With a foundation area of 1.50 mx 1.50 m , leave about 12 cm (or the width of a brick) from the edge. So you have a usable building area of approx. 1.20 mx 1.20 m .
Now calculate backwards:
A brick width as an outer shell plus 10 cm insulation layer plus 1 brick width fireclay results in a maximum combustion chamber of 0.9 mx 0.9 m . That’s pretty much exactly three and a half stone lengths per side and 12 stones per layer.
With a height of 50 cm or 4 layers, you get about 30 – 40 fireclay bricks that are needed to build the combustion chamber. An opening is left at the front . Traditionally, this is designed as a round shape in a wood-fired oven . However, if you do without the chic brick cladding of the stove and are content with plaster , the combustion chamber can be enlarged accordingly.
Of course, no Styrofoam or wood may be used for insulation . Even conventional roof clamping felt is not optimal for this purpose. The industry offers special “chimney wool” for this purpose . These ceramic fibers can withstand temperatures of up to 1400 °C. Please wear respiratory protection when processing !
The highly effective insulating wool keeps the heat where it belongs: in the wood-fired oven. Nevertheless, clinker bricks are ideal for the outer skin. Not only are they fireproof themselves, they also give the stone oven the right look. The walls are made of red bricks.
Tip: Used, old bricks give the wood-burning oven a particularly rustic look.
A 10 x 10 cm hole is left on the back wall of the combustion chamber in the top layer . That’s where the deduction comes in later . The brick base is left to harden for about 1 week.
The intermediate plate is necessary to prevent smoke from entering the baking chamber. After all, you build a stone oven and not a smokehouse. The intermediate plate is concreted. To do this, an auxiliary formwork is built : A board from a formwork panel is cut to size so that it abuts the inner wall of the combustion chamber. The board is held in place with two crossbeams and four supports.
Then a 10 cm high formwork is fixed to the outer wall with four boards of 20 cm width . Although formwork is traditionally nailed, we recommend fixing the boards with screws and dowels. This prevents you from breaking the bricks you just laid.
The resulting cavity is filled with concrete. Here, of course, refractory concrete is mandatory. A 25 kg sack of “furnace concrete” costs around 46 Euros. Here, too, the necessary stability of the intermediate plate is provided with two pieces of reinforcing steel mesh.
Tip: Lay a layer of insulating mat along the formwork from the inside. You can plaster them later. This prevents the formation of a thermal bridge.
The baking room is also constructed in three shells . It is constructed in exactly the same way as the combustion chamber, except that it does not require a vent. The floor of the baking room is laid out with a large fireclay plate . This is how you get the real stone base for the pizza from the wood-fired oven. The whole baking chamber is also approx. 50 cm high . An insulating layer prevents the oven from cooling down too quickly.
The clinker outer layer provides the rustic look and the stability of the building. The opening for the oven door should be kept as small as possible. It is approx. 50% lower than the baking chamber and 20 cm narrower on both sides than the outer wall. As a layman, you should be satisfied with a rectangular opening . The construction of the oven door is all the easier. Courageous and experienced do-it-yourselfers can of course also dare to try a classic round arch . This naturally gives the wood-fired oven a particularly traditional look.
Assembly instructions for the door
The door is particularly important in a wood-fired oven. It must seal the baking chamber tightly, but must not get too hot on its part. For do-it-yourselfers, making a traditional cast-iron door is of course not very practical. The solution is as ingenious as it is simple: a piece of dense insulating felt is ideal for building an oven door.
The piece is cut to size with millimeter precision using a cardboard template. It is then plastered on both sides with oven plaster and provided with two handles – done. The door looks good and is light as a feather. However, it should always be treated carefully so that the brittle plaster does not break off.
The heat from the combustion chamber must first work its way through the intermediate plate, then through the baking chamber and finally over the insulation above. As a result, only little heat arrives above the baking chamber. Inexpensive, conventional concrete can be used as the end plate here. The temperatures from the wood-fired oven have dropped so far at the top that even a wooden roof is possible.
For this you need:
- 2 formwork panels
- steel angle
- Concrete floor
- bitumen brick
- wood screws
- bitumen nails
The formwork panel is cut into three equal, flat, isosceles triangles. They form the gables plus a bracing in the middle. With a ceiling panel area of 90 x 90 cm , a basic length of 80 cm and a height of 60 cm is suitable. But there are no limits to the imagination. The gable triangles are each provided with three angles.
The angles are attached to the inside and must not protrude. The triangles are then firmly connected to the cover plate with the angles and the concrete dowels. The triangles are shuttered with the on the sides. The bitumen tiles are then nailed to the roof from the bottom up and overlapping – done.
It is advisable to use a specially developed flue pipe for the wood-fired oven . It has the necessary material strength and other properties optimized for this purpose. The smoke tubes are sold in sets. Assembly instructions are always included. The set also includes all the necessary components for the connection.
It may sound strange, but many wood-fired oven builders insulate the plate between the firebox and the oven cavity. This means that more energy is required to get the baking chamber to the desired temperature. However, the heat then stays in the baking chamber much longer . A constant temperature in the baking chamber is very important for a successful baking experience.
If children are near the wood-fired oven, the flue should be insulated. It can get very hot. Insulation not only eliminates the risk of injury. The trigger also “draws” better because the smoke doesn’t cool down as quickly in the tube.