My Bushfire Bunker By Samantha Duzenman The idea for my bunker was to have it under ground. I was initially going to have it as a concrete cube structure above ground but then decided that the natural insulating properties in the ground is much more efficient. I have created a bunker that can be built onsite. It is made completely of concrete and stone. The main area was going to be an existing cement water tank. However I spoke to a builder and he says that they are hard to move around (especially to more regional areas) and it would just be cheaper and easier to build onsite. He also said something like this would take approx 1 month to finish. I have designed my bunker so that you can have the option of excavating approx 2.2m into the ground or you can create a man made hill around the bunker. The builder I spoke to said it would probably be cheaper and more efficient to have the man made hill. In such intense heat, steel tends to buckle and lose its structure. So, for the trap door (the alternative entrance) it will have to be reinforced with a slab of concrete over the top. My bunker also doubles as a wine cellar. When you go through the main entrance you walk down the stairs with the wine stored on shelves and at the bottom of the stairs is a second sealed door and then you enter the cylindrical bunker (main area). The main cylinder is completely made from concrete poured into the ground and against the soilâ€™s walls approx 30cm thick concrete. The cylinder for the alternative entrance from the trap door is molded with the main cylinder. The builder said this would be pre molded and then added to the main cylinder. He thinks anything like this might cost $40,000 + because of the concrete structure, heavy sealed doors, utilities and excavation.