Levitate Architects used a staircase to a loft-like bedroom to create an enormous amount of book storage space. Even though the staircase isn’t very compact but could accomodate so many books that it would save some space anyway.
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Staircases take up a lot of space, so why not use them for storage as well. Imagine each step is a box with a hidden drawer in it still allowing for additional storage or home office space beneath the staircase.