DIY Bike Rack for $20 / Bike Storage Stand & Cabinet for Garage : 5 Steps (with Pictures) - Instructables

You'll need roughly 12" of space per bike, plus 12" on either side of the bikes on the ends. For example, my 5 bikes needed ~7 feet of wall space. For my area, I used two 8 foot long 2x4s and cut them each down to roughly 84". The upper 2x4 should be mounted roughly 14" above the lower 2x4. This will stagger your bikes so that their handlebars don't clash.