Plan shelf spacing for books, decor and storage boxes.
Shelf spacing is a subtraction problem people usually get wrong by forgetting the shelves themselves. Each shelf consumes its own thickness, so five three-quarter-inch shelves in a 72 inch unit eat 3.75 inches before anything is stored. Take off the base clearance too, and the remaining height divided by the number of shelves is the actual clear gap. Compare that against your tallest item plus an inch of lift-out clearance, and you know whether the plan works. For reference: paperbacks want 8 to 9 inches, hardbacks 11 to 12, LP records 13, and storage boxes or files 13 to 15. Uneven spacing usually beats even — one tall bay at the bottom and closer shelves above stores far more than a uniform grid.
Shelf Spacing
Usable height = unit height - base clearance - shelves x thickness; gap = usable height / shelves; max shelves = (unit height - base) / (tallest item + 1 + thickness)
Nine inches clear for paperbacks, 12 for hardbacks and 13-15 for files, records and box storage. A mixed collection is best served by graduated spacing rather than a uniform grid.
Three-quarter-inch plywood or MDF spans about 30 inches loaded with books before it visibly sags; solid timber manages a little more. Beyond that, add a centre support or a front edge lip.