A home office is a room that many people find beneficial. For those that work from home, it provides a workspace away from the rest of your home and other family members, which can add a degree of professionalism if you have customers visit your office. Even for those who work outside the home, an office space can provide a place to study, do work-related tasks or do simple household tasks such as pay bills. A garage can be an ideal place for a home office as it often has a separate entrance so clients don't have to enter your home.
Design the layout of the garage office. If using only a part of the garage as an office, mark the location of the wall or walls you need to build to divide it, as well as how you intend to have the office set up.
Decide which parts of the construction you'll do yourself, and what you'll hire a contractor for. Local building codes often require that plumbing, electrical, and heating, ventilation and air conditioning (HVAC) work be done by a certified professional. Tasks such as laying a new floor or building an interior wall can be done by someone with intermediate do-it-yourself skills.
Clean out the garage so you have room to work. Donate or sell any clutter that you don't need.
Get any needed electrical, plumbing or HVAC work completed. A home office most likely won't require plumbing work, but you'll need electrical work and HVAC work completed so the garage office is a comfortable place to work.
Inspect the floor of the garage and make any needed repairs. You can patch small cracks yourself by digging into the floor beneath the crack and filling it with patching compound. If the cracks are larger than an inch, have them inspected and repaired by a professional, as it can be a sign of bigger problems with your foundation.
Remove any signs of the garage door. There are basically two ways you can do this. The first way is to completely remove the door and the hardware, then build a wall over the hole where the garage door was. Your second option is to remove the hardware (the tracks) and build an interior wall over the garage door to hide it.
Finish the exterior walls of the garage and build any new walls that are needed. Build the new walls by constructing frames -- adhering to local building codes -- then connect them to sill plates on the floor. Insulate all of the unfinished walls, and cover them with drywall.
Paint the ceiling and walls with two coats of primer -- allowing each coat to dry thoroughly -- followed by the paint colour of your choice.
Install the new flooring. A tile or hardwood floor is easy to clean and can work well in a home office.
Consult your local zoning board to acquire any needed permits and to learn the building codes you must follow in constructing the office garage. Contact an accountant to see if you can write off the construction costs for your home office as a business expense. There's no guarantee that you'll be able to, but you have nothing to lose by asking.