Detached garages fall into two categories. Those located near the house, often set back from the road but well overlooked by surrounding houses; and those located at the rear of the property and accessed by a service road.
These latter types of garage are likely to be an easier target for thieves due to them being out of sight, with trees and high hedging at the rear of gardens obscuring them.
Garages connected to the house very often will have a connecting door to the main house, so care needs to be taken over the type of door fitted. A dual certificated door for both fire and security is recommended (link to more information at Guidance and Standards)