Space above a double garage can provide room for an apartment, office, storage or hobbies. The floor space included in a double-car garage can be extended out a few feet on the second floor to provide lots of room. You can build an area with two or three rooms by thinking ahead. If you live in an area where building space is limited or property is costly, building over the garage is a good option. You can design the space to be completed in manageable stages over time or finish all of the space when you build the garage.
Visit websites for interesting floor plans for rooms above a garage. Gather ideas that might work for the kinds of activities you envision. Review home design books and magazines to see what types of rooms can be built in a loft or second-story space over a double garage. Sketch pictures of your existing home and the type of garage you want to build. Convert your sketches to graph paper once you've defined an actual design, since you need to make sure the exterior of the garage and overhead addition look proportionate to each other.
Make interior sketches using the dimensions of the garage and the floor plan dimensions of the building space above it. Create a list of activities you picture using the rooms for. List cooking, sleeping, office work, sewing and hobbies. Divide up the space using graph paper and design doors between the rooms. Be sure to include exterior windows for all rooms as well. Plan where electricity and plumbing will be routed in the space as well.
Consult with a builder to make sure the garage rafters and side walls will accommodate the weight of the rooms you have in mind. Consider using larger ceiling rafters for the garage to add extra insulation. Avoid having car fumes move into the attic space rooms above it by sealing the garage ceiling with sheets of plastic or styrofoam. Design the upper floor rooms above the garage using graph paper for every wall and every room from a bird's-eye view.
Include windows on at least two walls of the building space in case you need a fire escape. Check local building codes to ensure you are following necessary building guidelines regarding windows and doors, plus all safety requirements. Use lower spaces below windows for bookcases, media cabinets and storage. Build a row of several side-by-side windows, if possible, for a hobby area or work desk. Design at least one bathroom in the overall space.
Anticipate where the rooms will be accessed from below. Design a set of stairs from outside the garage, if you have room. Place those stairs on the side of the garage that will be visible from the house for security reasons. Plan to purchase a steel door as the main entry door of the space above the garage and install a burglar alarm for added security.
If you plan to include skylights in any rooms above the garage, make sure you purchase skylights with 12-inch flashing to prevent leakage from rain over the years. Add smoke detectors and fire extinguishers to the rooms for added fire protection.
Don't necessarily assume you can build an apartment for actual living above a garage. Check with local building authorities to see what's allowed in your area. Don't assume that sleeping areas can be built there, either, since a garage can produce fumes and carbon monoxide. Review all regulations with city officials.