The minimum requirement for any two-tier bicycle rack should always be 2600mm of clear height. This dimension is based on the size of a bicycle. We allow the internationally recognised size of a 1200mm tall bicycle, this accounts for larger sizes of bikes, ensuring any cyclist can park any bicycle in all available parking spaces.
Stack one bicycle on top of another directly, and this equates to 2400mm of height, however, the design of two-tier parking racks incorporates a high-low stagger on both the upper and lower tiers, this stagger is to prevent handlebars clashing when creating a closer centre to centre distance between bicycles.
This stagger distance must be a minimum of 200mm in order to avoid clashes of handlebars and ensure access. When this 200mm stagger is accounted for, the end result is a minimum headroom requirement of 2600mm.