A friend built his house around an 8'x15' room made from steel reinforced concrete walls and ceiling intregal with the concrete slab. It has a vault door disguised as a regular door. Inside the room he has his old gunsafes which contain valuable books and his best guns. The rest of the guns are in wall racks. It didn't cost much as it was built before the house. It's a great set-up and has a substantial fire rating.