Examine the carport foundation carefully to ensure there is no cracking. Ask a concrete mason to offer advice if you're unsure whether the concrete foundation is thick enough to support new framework, house siding and the garage door. Add 4 inches of concrete reinforced with rebar, if necessary. Be sure to remove old concrete completely to pour a new floor if the old floor has serious cracks and gaps.
Check the structural strength of the existing carport framing. Figure out if roof rafters are installed on the recommended 16-inch centers, so you can install plywood sheathing and asphalt shingles, for example. Work on enclosing the wall framing first, however, because wall framing must fully support all roof weight.
Cut and install wall studs from 2-by-6-inch boards around the enclosure, leaving the main garage door opening and an opening for a walk-out door as well. Install 2-by-6-inch framing boards for the enclosure framework, versus smaller 2-by-4-inch boards, to accommodate door weight and any siding on the structure. Construct the main door opening and side door opening by nailing king studs from the top plate to bottom plate to define the door width. Cut a header board to fit across the top edge of the roll-up door and walkout door.
Frame any planned windows by cutting king studs from 2-by-6-inch boards as well. Cut and nail into place headers to fit across the top of the windows.
Cut additional rafters, if needed, to strengthen the carport framing for the enclosure. Nail ½-inch plywood sheathing over the roof of the building. Enclose the roof overhangs to match the house overhangs, so the new enclosure looks original to the house construction. Cover the sheathing with roofing felt and install asphalt shingles or metal roofing, as possible choices.
Install the garage doors and windows before nailing house siding on the exterior. Screw the garage door tracking to attic framework with 4-inch screws, following the manufacturer’s instructions. Ask an expert to help you install the garage door tracking because any margins can cause the garage door to slip off tracking and fall, possibly injuring or killing someone. Cover the new building enclosure with tongue-and-groove boards, siding made from cement fibers or vinyl siding. Add door and window facings and trim as needed before staining or painting the structure.
Install the automatic garage door opener after you have added any interior finishing. Run wiring for the automatic opener through the attic of the space before nailing sheets of drywall in the ceiling area. Install drywall on walls of the structure, if you desire, and paint the concrete floor with epoxy paint.