In the garden shed, which has been a bike shed since we bought this house! At one time, there were 9 bikes in there; now there are 5. DH's 3 are hung on hooks, on the right side. My 2 bikes are in floor stands. I am not tall enough to get a bike down from the hooks.
Once the snow flies, our carbon bikes live in the house, on trainers in our loft, which has other exercise stuff up there. If we have a +35 degree day and snow free roads, we ride our titanium bikes.
The shed has a key padlock, but our house is kind of secluded, so we often leave it unlocked if we go out for a short ride, or if DH comes home before me when I am commuting home.