Angle iron and 4″ solid concrete block oven hearth base. This sits on top of 8″ concrete block walls.
I lead this workshop in April 2017 at the Masonry Heater Association annual meeting at Wildacres Retreat in Little Switzerland NC. Heater and Oven builders from all over the world make a pilgrimage to the top of the Blue Ridge Mountains to share their knowledge with other like minded smoke benders. We build around 6-10 different masonry heaters and ovens, learn new technologies and techniques, share stories with old and new friends, burn fires, and have a wonderful time during the 7 day event.
For this workshop we decided to build a historical Squirrel Tail bake oven. The squirrel tail design has been used all over Europe for 100’s of years. The squirrel tail name comes from the design feature with the channel or channels of the oven exiting from the back of the oven and following the top of the oven and then exiting into the chimney in front of the oven. So that is looks like a siting squirrel with its tail curled over the top of its body and then curling up again. This particular design comes from the Tyrolean Alps Region between Austria and Italy. The inside of the oven is typically shaped like a pear. With the chimney exiting out the back channel or channels in a larger oven, and then being directed over the top of the oven this helps to create a strong draft. This design keeps the smoke and fire away from the door area where you are baking so that you don’t have to worry about smoke in your face. With the hot gases from the fire being burned on the inside of the oven dome and then being directed into the chimney channel on the back of the oven and then over the top of the oven the bricks are heated up from both sides. You are using more of the heat from the wood for better efficiency.
The nature of this simple design keeps tools and materials at a minimum for ease of building. We use medium duty firebricks and soft solid red bricks for oven construction. Soft red bricks have been used all over the Eastern US and are still used in Europe. Hard red bricks will not work for this application. A standard Type S Hydrated lime mortar is used to set the bricks with and the only tools used are a brick trowel, brick hammer and a mixer to mix the mortar with. A mortar tub or wheelbarrow and shovel could be used to mix mortar with as well.
Oven foundation walls and hearth base in place. 2″ of Calcium Silicate insulation board is set on top of 4″ CMU base and then a course of firebricks for the hearth are set on top of the insulation. Historically they have used a thick layer of clay and straw for the insulation base and wood timbers for the hearth base structure.
Sawdust oven arch form
Next step is to build the oven entrance ~18″ wide x 12-14″ tall. Then we lay a course of bricks on the outer wall to give the oven its pear shape for good combustion and heat radiation. We use wood shavings or saw dust to form the oven dome. A piece of wood is cut to 18-20″ and propped up in the middle rear 1/3 of the oven to use as a height guide for the saw dust form. The saw dust is dampened with water to help hold its shape and formed into a pear shape with the high end in the back of the oven and the form tapering to the front door entrance. We use sawdust because it is lighter and easier to remove than sand. If some of the sawdust gets into the mortar joints it just burns off in the fire. If you used sand then any residual sand could end up on your pizza or bread.
Paper is laid on top of the sawdust form to help keep the sawdust out of the mortar.
Bricks are set in a 1 part lime and 3 parts sand mortar and are set to the sawdust arch form. Mortar joints on the inside of the oven should be squeezed to ~1/4″. Since to oven is shaped like a pear, your mortar joints on the outside of the brick will be bigger. So we just use more mortar on the outside or you can fill in with brick chunks.
Lots of projects being built
For this larger size oven we need 2 channels for the chimney. One on the left and right rear side of the oven. The rule is that the bottom of the chimney channel exits have to be 1-2″ higher than the front door of the oven and the top of the chimney exits need to be 1-2″ below the top of the oven dome.
Oven exits in place and continued brick courses going up the oven form.
Oven form is finished with brick and now the squirrel tail chimney channels are being built over the top of the oven dome.
We level off the top of the dome with brick and mortar to the front of the oven door where the chimney will be located.
Squirrel tail channels being built over the top of the oven dome. Both channels converge at the front of the oven to transition into the chimney.
Channels are then capped off with brick.
After the chimney channels on top are built and the dome bricks have had a day to set we scoop out the sawdust arch form. We use a small hoe to scrap out the sawdust and then you can use the hoe to scrap away the residual mortar on the insides of the brickwork.
Small curing fires are then started to cure the oven. This is only a 7 day event so we start curing the oven immediately so that we can use the oven for our Fiesta de pizza party on Friday evening. We would normally cover the oven with a tarp to cure for 7-14 days before we start any curing fires.
The beautiful curve of the flame dancing over the top of the pizza.
Curing fire moved to the back of the oven gradually.
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