Efficiency of pizza oven depends largely on hearth and insulation system. Hearth gives supporting structure to the oven because on this part dome is placed. Again efficiency of hearth affects by its insulation material and thickness. By keeping this in mind everyone makes proper insulation under hearth of pizza oven. Normally, vermiculite is used as insulating material in pizza oven and it is also used to insulate under hearth as well. But the thickness is quite difference than other parts of pizza oven. At first, vermiculite and Portland cement in a ratio of 5:1 are mixed properly. It is done by shovel because automatic mixer may affect the insulating property of vermiculite. Then dry mixer is remixed by adding water when ratio will be 6:1 (dry matter: water).
A metal mesh is placed on the stand of pizza oven. Then vermiculite mixer is poured on mesh. This mesh will help to hold insulating mixer properly and also give strength to the structure. This thickness of vermiculite will be three to four inch. This thickness is sufficient to hold proper heat inside of the pizza oven. After placing vermiculite mixer you have to allow two days to settle properly. Then you should work on hearth for placing dome.