There's a company in Germany making collapsible garages that would have to be bolted onto a fixed wall and are just big enough for bikes. Looks pretty neat - I wonder how much.
https://www.youtube.com/watch?v=KrzeIC5gg-w
Their website: http://translate.google.ca/translate?hl=en&sl=de&u=http://www.die-motorradgarage.de/&prev=search
https://www.youtube.com/watch?v=KrzeIC5gg-w
Their website: http://translate.google.ca/translate?hl=en&sl=de&u=http://www.die-motorradgarage.de/&prev=search