A brick pizza oven dome is usually constructed as either an igloo or barrel dome. Both shapes are constructed in much the same fashion with bricks, mortar and usually with a supporting frame. Construction of an igloo dome does not necessarily require a frame if completed by a competent brick layer. Fireclay or refractory mortar is not normally required. Some cracks may develop with regular building mortar however these will be within the oven and not readily noticeable.
After constructing the internal brick wall you will need to cover the brick with an insulation layer to further improve the heat retaining properties of the oven.
Once the hearth has been establish you may begin to build the wood fired pizza oven dome. Domes constructed out of cob usually consist of clay, soil water, and hay to act as a binding agent. As cob is a soft and malleable material before it dries, a supporting foundation is usually created to hold the cob in place during the construction and drying phase.
Begin by placing moist sand as a mound onto the hearth. The small amount of water will allow for the sand to be molded into place. Continue to add sand to create a mold of the inside of the pizza oven. You may want to make use of a piece of wood with a curve sawed out to help model the send into a uniform shape. Keep in mind that the walls of the pizza oven will be placed on this sand mound and thus the final size of the oven will be substantially larger. When the sand mound is complete, place wet newspaper over the mound. The moisture will keep the paper in place, and the function of the paper will be to allow for easy removal of the sand at a later date.
Allow the oven to slowly dry oven a period of days. If the oven dries too quickly then the likelihood of cracks occurring is increased. Once the oven dries you can repair any cracks with additional clay, and carefully remove the sand and newspaper from the oven door.