Mine are in a 11 x 8 x 8 Brick build shed with a concrete floor. All three bikes are locked together with a Magnum lock, which is threaded through a loop sunk into the concrete floor. The door has a proper lock at the handle (not Yale the square bolt type) and two locks top and bottom.
You can only access our garden from our side gate which is bolted an locked.
My view is, if they get my bikes out through that lot, there wouldn’t be much more I could have done to stop them.
**Another thing BTW – its been noted that increased hacking/exposure to online software such as endomondo (for example) allows theives to see where you live – make sure your privacy settings dont allow all and sundry to see your maps.