Adding a garage to a home can require an extensive amount of work, and for this project we will assess the cost of building an attached garage of 676 square feet (26’x26′) to a pre-existing home (this is going to easily accommodate two vehicles, provide storage and even have room for a small work area). There will be only minimal “finishing” work done to the interior of the space in order to keep constructions costs in check. Garage addition projects are never considered “DIY” projects, and several contractors will be necessary for the job (concrete, carpentry, electrical, etc.).

 

For the garage addition, the typical costs include:

• According to author Stu Silverman the average cost of adding a garage begins at roughly $7,500, and for a two-car garage the average costs will go much higher. This sort of structure will average at $27,040. The resale value of this update would hold at $21,635, or a nearly 81% return on investment.

• The above figures place the garage addition at $40 per square foot. This pricing structure assumes that carpenterscharge an average of $70 per hour, electricians between $65 to $85 per hour, and painters between $20 and $35 per hour. Traditionally, most homeowners tend to work with a single contractor, who identifies suitable subcontractors and pulls proper permits, for such a project.

 

Cost breakdown

• Arrange any required demolition, excavation, or site preparation – Average costs are going to vary according to the level of work necessary;

• Pour concrete footings and slab – Average price of concrete is $75 per cubic yard, with piers and the full slab it that would require roughly 20 cubic yards and would cost at least $1500;

• Build roof trusses and support beam system and tie into existing house – lumber prices will vary as will the design used by the carpenters constructing the garage. The project should require 2×4 wood framing with OSB structural sheathing and a gable truss roof at 6/12 pitch;

• Asphalt shingles with galvanized metal flashing – Average of $80 to $100 per square of 50-year shingles. Total cost of $800, plus installation time of at least 16 hours;

• Install vinyl siding and trim – Average price of $7 per square foot installed, and for the 920 square feet needed, this would total $6440;

• Install five double-hung 30-by-48-inch vinyl windows – Average price of $300-$700 per window, plus installation time of two to five hours per window. Be sure that the windows purchased qualify for tax deductions;

• Install one 3’x6’8″ exterior door with half-glass and lockset – Average of $250 to $1000 depending upon the style of the steel door;

• Install two composite 9-by-8-foot overhead doors with motorized openers – Average between $399 to $899depending upon the quality and design of the individual doors;

• Provide electrical wiring and lighting to code – This is going to depend upon the amount of work required, and must include a 100-amp breaker at main house panel. Electricians average from $65 to $85 per hour. This project might be priced on a per item basis, or the electrician might simply base it on the square footage; and

• Provide carpentry to code – This is going to depend upon the amount of work required, but carpenters average $70 per hour. This project might be priced on a per item basis, or the carpenter might simply base it on the square footage.

 

Additional considerations and costs

• Finishing of interior walls, floors, and ceilings;
• Installation of heating system;
• Installation of electrical wiring for openers, three-way switching for fluorescent ceiling fixtures over each bay, and three-way switching for two exterior spotlights; and
• Installation of gutters and eaves.