Secure a Permit
Before you start to build, draw up your plans on paper and submit them to your municipal authority to acquire the building permit necessary to add a garage to your property. Then have a cement pad poured at least 4 inches thick with a slope of one inch for every 10 feet, for drainage.
The next challenge is to calculate the wall height needed to create a 12-foot ceiling on your garage. If you have not already poured your foundation, be sure to add at least 1½ inches to your calculation for your desired ceiling height.
For a garage with a 12-foot ceiling, you will need a total wall height of 13½ inches, for example. Cut your studs 4½ inches shorter than that to accommodate the wall frame's top and bottom plates.
Framing a garage takes strength, precision and manpower since it must be square and accurate. All plates must be pressure-treated to handle moisture, and they must break at the right places to preserve the strength of the structure.
Header beams are needed over doors and windows. Once frames are up and secure, add the sill plates and then roof trusses.
Install plywood over the trusses and cover it with roofing material. Finish the structure with paint or stain and trim of your choice.