To compute the cost of building a basic garage, add together the prices for the foundation, building materials and construction. Common building materials include lumber, siding, roofing, doors and windows.
Contact a concrete contractor to get an estimate for the foundation or slab of your garage. The contractor considers the size of the garage, code requirements and land-preparation costs. Expect higher costs if your local building code requires a full foundation.
Use your garage plans to make a list of materials, and estimate the required amount of each material, rounding up to account for errors. Consider the studs, wood for the frame, plywood, insulation and wiring supplies. Add the siding, roofing materials, ventilation equipment, hardware and interior finishings. Finally, add in the siding, entry doors, garage doors, windows and overhangs. Bring your list of materials to a building supply store, and ask for a cost estimate.
Complete the cost estimate by pricing construction costs. If you are building the garage, add costs for tools, supplies and supplemental labor. If you are working with a contractor, request estimates based on your chosen materials and the size of the garage. Add together the foundation costs, material costs and construction costs to determine the overall price of the garage.