Designing a detached garage requires a few considerations. Always have future use in mind. That means that you need to consider your storage need aside from the vehicles and whether or not you will want to put a living space in the garage as well. Future use also means keeping the car count in mind as you lay out the footprint. Your teenager may not have a car now, but when he does get one you will want to have room in the garage for it. When he leaves to go out on his own, you can use that extra space for a workshop.