Doors can be a nice feature of an oven. They can be steel, refractory cement, refractory insulation cement or protected wood.
Its job is to keep the heat in the oven and act as a damper for the fire if required (i.e. restrict oxygen getting to the fire so controlling combustion levels). The door is also an important safety feature to help stop embers and burning bits of wood exiting through the entrance.
We recommend a door made from refractory type concrete as it works in with your oven to retain and radiate heat. Just be careful as the handle gets hot.
For cooking pizzas a door isn't really necessary and can just get in the way, but they are worth having to help keep the rain out when the oven is not in use and for other types of cooking where you want to slow the heat generation part down (ie slow cooking).
Our kit set door mould system means you can easily create a door that fits and performs well. The kits create a door that is 50mm thick, so will stand on its own and is unlikely to blow over.