Adding a home office or workspace above your garage will also increase the value of your home without changing the floor plan. Following are some ideas for your detached home office.

• Before you decide on expanding your garage, consult with a building contractor or structural engineer. Some garages may need extra structural support before they are able to accept an addition.
• Use a designer or architect to help with the addition plans. He or she can add esthetically pleasing elements without sacrificing the structural integrity of the building.
• Rather than building a two-storey box, add dormer windows and sloping rooflines to dress up the exterior of the addition. Have the designer match the addition to your house. The addition should look as though it is an original element of your home's design.
• If the space can also be used as a children's playroom or sitting room, built in storage shelves or cabinets can help reduce clutter.
• Plan for plenty of electrical outlets and additional phone lines. You will need extra lines for computers and fax machines. It is less expensive to put extra electrical lines in before the drywall is installed.
• If your budget allows, consider having a covered walkway or bridge built to tie the addition to your home. The architect should pay special attention to outside stairs. A mismatched staircase can interfere with a good building design.
• A pricey, but worthwhile option is to install plumbing in the addition. This will increase the value of your home and allow the room to be converted to an apartment for an older child or to be used as a rental unit.
• Look at the existing garage door. If it is a basic metal door, replacing it with a wood garage door will dramatically change the look of the addition.

-- Tips courtesy of HomeAdvisor.com