How to Calculate Cost of Adding an Attached Garage

As you calculate the cost of building an attached garage, you need to consider every step in the construction process and make choices of materials and optional features. Contact several suppliers to find out the cost of each component and then factor the number of each item you will need to build the garage.

Determine the dimensions of the attached garage. Dig your footings by hand, or rent a backhoe with a narrow bucket to do the work.

Buy 2 by 4 wood beams and ½-inch plywood for the footing forms. You will need forms on the outside and inside of the footings.

Mix the cement yourself or call a local cement company to deliver the premixed product. Determine the number of cubic yards you will need for the footings and the floor when you figure the cost to build a garage.

Calculate the cost studs, sheeting for three walls and the roof, shingles, at least one vent for the roof, approximately 5 lbs. of number 8 box nails for the sheeting, 5 lbs. of number 16 nails for framing and roofing nails for the shingles. Use treated 2 by 6 wood beams for the plate on the bottom of the studs, and install bolts about every 3 feet to hold the frame into place on the cement.

Decide the width, height and style of garage door. Optional costs include an automatic garage door opener, service doors and lock set, windows, cabinets, shelves, workbench and hardware to hang tools.

Choose the material you will use to finish the exterior when you calculate the cost to build an attached garage. Match the siding, trim and eave troughs to match the existing house.

Finish the inside of the garage beginning with ¾-inch drywall for a firebreak between the garage and house. Use drywall screws, a power drill and screwdriver. Drywall the rest of the garage, tape the joints, cover them with joint compound, use sealer and then paint the walls and ceiling.