Its just studs and outer skin... I actually thought about doing exactly what you did with the diamond plate on bottom. I was thinking I might be able to use the stuff that is used in bathrooms... that shiny white "stuff".
Steve
If your talking the white press board stuff... dont. I tore that stuff down(I put that up first) because if it gets wet.... it gets bad and buckles... but I had a roof leak... which I fixed. I bought the diamond plate from Jack Moore here on the board, he's in the Columbus area.... very good price and he also can get the white alum... I'd talk to him FIRST. Make sure you insulate it also, I used 1" of the blue styfofoam on the walls and ceiling
I actually thought about doing exactly what you did with the diamond plate on bottom. I was thinking I might be able to use the stuff that is used in bathrooms... that shiny white "stuff". 
