Floorspace in a garage area can be more valuable as living space. As your family grows, you can turn an existing garage into one or more bedrooms. Later, you can build a free-standing carport or a detached garage to protect your cars. Building bedrooms in garage space should be more cost-effective than building from scratch.
Design a floor plan for one or two new bedrooms that will include a bathroom and closet space. One option to offer privacy in the new area is to design a hallway leading to the bedrooms. This will be needed if your garage is near your kitchen. Sketch walls, windows, light fixtures and electrical outlets into the plan. Figure out your source of heat and allow space for vents or wiring in your plans.
Begin to build the area into livable space by enclosing the exterior garage door space. Save or sell the garage doors. Knock out areas to accommodate new windows, if needed. Once the garage space is enclosed from the elements, frame all interior walls and install electrical wiring and fiberglass insulation between studs.
Create space for plumbing and pipes, if you are building a bathroom. You will need a jackhammer to break through an existing concrete floor. Place the bathroom near an interior wall that presently carries pipes. Or, create an interior wall to hide pipes and drains.
Install light fixtures and all electrical plugs and outlets. Attach drywall to the ceiling rafters and over all framework around the walls. Finish the drywall with joint compound, sanding and painting. Use flat or semi-glass paint. Connect to a heat source through new venting. Or, install an electric heater on the exterior wall of each bedroom.
Install wooden flooring in the new bedroom areas. Call in a pest control company to help you pre-treat for termites in the event you are laying wood over concrete. Place the commode, shower and sink vanity. Caulk as needed. Install baseboards, molding and trim work in the finished areas.