As with building a house, one of the first requirements for adding a garage is to obtain approval and building permits. Check with your local planning department for details specific to your city. If your neighborhood has a homeowners association, you must also get approval from the body before making structural change to your property.
Enlist the services of an architect or engineer to ensure that your potential site can accommodate the full-size garage that you seek. A typical single-car garage is 14-by-20 feet and a modest double garage requires 20-feet-by-24 feet. Assess your site for a driveway. If one is not in place, this is another expense for the project.
Garages present multiple options for its use, as well in its physical design. Decide whether you want an attached or detached garage. An attached garage offers the benefits of access to the house without exposure to the elements and it generally costs less. A detached garage can offer some protection from the elements if constructed with a breezeway, and it keeps exhaust fumes and dust from entering the main house.
With preliminary details secured and a good idea of what you want, find the best person to execute the plan. Meet with several contractors and obtain bids on the job. Be sure to get thorough answers about the construction timeline, including start and completion dates, and the contractor's payment policy.
Once you know what you want built and have estimates of what the project will cost, you can plan how to pay for the addition. If the project is not paid for in cash, a home equity loan or a construction loan are two options to consider.
When construction gets under way, stay in contact with the contractor to make sure the project is progressing on time and within budget. Expect the project to start with excavation and pouring footings and foundation walls and then moving on to framing.
Plan for two inspections during the garage addition, the first when the framing is complete and the second when the job is complete. The final inspection will allow you to legally occupy the space. Some cities might require inspections for other phases, too, such as plumbing if installed and electricity.