After the 26 inches of rain in 24 hours I have to rethink my base .. The base is done and I will not be placing a roof over the finished oven .. No room . I thought I would pour a 2 inch thick slab [platform] the shape of the finished dome on top of the base . under this I would put some roofing material [[this is heavy material used for flat roofs not tar paper]] . so the concrete platform won`t allow water to soak into it from the base ..Then some aluminum sheeting over the platform before putting down the the 3 inchs of fiber board and fire brick after that ..... I would also seal the outside edges of the raised concrete platform . I was thinking about vermiculite concrete but a regular pour with gravel would be stronger for the weight of the dome , and I don`t feel I need the xtra insulation .any and all coments are appreciated .. For those you that have answered my ? before thank you . I had hoped to start this several months ago but life sometime dictates other needs ..