Everyone, Marco's link is in Italian.. I'd like to get a piece of that translated by someone who knows italian...
I don't speak Italian but Google machine translation seems to have done a good job creating something that reads quite well: I am too new to the forum to post links. So here is a bit of the translation:
"Located the best place to elicit materials. We recommend the full facts bricks by hand as compared to those industrial printed, better to resist high temperatures. The bricks made by hand have the advantage of warmed more slowly and retain heat longer, while those for industrial printed, excessive compression dell'argilla can block the thermal expansion and cause the rupture of brick. You can also choose refractory bricks designed to resist high temperatures up to 1600 °, however, have the defect to store and dispose heat faster....
The construction of the furnace begins with the support base that we recommend it wider diameter of the furnace at least 15 - 20 cm also to have a plan and support always helpful about 1.2 meters high from the ground.
Above is the basis of a plan drawn tiles and between the base and the tiles need to put a thick layer of insulating material like clay or expanded vermiculite, all held together with refractory cement and sand. It is important that the plan is perfectly horizontal oven to cook with ease even initially liquid foods such as farinata.
At this point we must build again. The dimensions depend on the furnace circumference at the base and the height of the vault.
The height of the vault to the top domestic yields with the formula:
H = d / 3.4 where H is the height of the vault and d is the diameter of the furnace in centimeters. However, the height of the vault must never fall below 25-30 cm. For example, in an oven to 110 cm in diameter, the height of the vault will be 40 cm.
We must ensure that the center of the base of the oven near the fire of time which usually is a paraboloid in order to concentrate reflection of the warmth of time on the hob.
To construct the time we start making a base of wet sand or earth very compact size desired, be shaped in the form of a paraboloid, (the secret lies in being able to properly shape the dome of sand, is a bit like playing build casteli sand on the beach) on which the bricks will support the vault of dish, held together with cement mortar or refractory with a mixture of clay mixed with a little sand. The bricks are arranged staggered starting from the bottom to rise to follow the curvature of the sand. Once the structure is completed, seated hardened and will be used to remove the sand from support.
The size of the mouth also depend on the diameter of the oven, on what you intend to cook, and the size of pans you want to insert. An oven with a diameter of 120 cm. Should the base of the mouth of at least 50 cm. And a height of 28 cm. Even the shape of the mouth is influenced by the location that you wish to give the oven. The ovens for baking bread and pizza prefer mouths shaped isosceles trapezoid, but rectangular, while the ovens for cooking foods like sweet and farinate prefer opening-shaped semicircle slightly crushed in the middle.
After the construction of the time, you should cover of insulating material that retain heat. To do this is a good layer of clay often expanded about 12 or 15 cm. Si puo' anche usare della vermiculite. You can also use the vermiculite. It then covers everything with a layer of brick or other material with aesthetic and decorative function.
The chimney. Its construction began providing a small fume hood from place between the time and the mouth of the oven or on the side and which builds the real chimney. The rules apply to the views fireplaces and stoves. I preferred smoke pipes insulated and circular section. The diameter of the chimney, indicative, it is clear from the table below, pointing out that the draft is directly proportional to the chimney. "
I hope Marco is not falling of his chair with potentially poor translation of some of writings