DIY 3 Car Garage Plans

Design

• Design the garage to have three separate overhead doors, or a combination of single and double overhead doors. The minimum width for a three-car garage is 30 feet, which provides a close fit if also used for storage. For adequate storage, a width of 32 or 34 feet gives you more than enough space. Make the depth at least 24 feet deep.

Foundation

• Set out the lines for the garage foundation. Excavate the hole, pack the soil and fill with gravel. Use rigid foam board to insulate the garage floor. Construct the concrete forms out of 2-by-12 boards. Place stakes at 36-inch intervals to secure the forms. Use rebars to strengthen the concrete. Embed the anchor bolts for the wall sections' bottom plates in the wet concrete approximately every six inches and within 12-inches of any breaks in the bottom plates.

  Start framing the wall section after the concrete has cured. Lay out the bottom plates and drill holes in the boards to ensure the right fit. Do not secure the plates in place.

Walls Sections

• Frame the wall sections using conventional standards, including the window and doors rough openings (RO). The wall for the overhead doors may have a few variations from the standard. Use 2-inch by 4-inch lumber for the wall sections. Make the length of the studs eight feet. Cut the top plates and bottom plates the same length. The bottom plates must be treated lumber, because they will come in contact with the concrete foundation.

  Place the two plates side by side and mark the placement of the studs. Place studs 16 inches on center (OC). Measure OC from the center of one stud to the center of the next stud. Read the door or window product guidelines for RO dimensions. Generally, add two inches to the RO width and one inch to the height for doors. Construct the headers for the windows and doors out of two 2-by-6 boards. Add a ¾-inch thick plywood spacer in between so that the headers are the same thickness as the walls. Place sill foam over the bolts, which will serve as an underlayment between the concrete and the wall section bottom plates. Use 2-inch by 4-inch lumber to brace the wall sections.

Overhead Door

• Use two 2-inch by 12-inch boards or prefabricated beams for the overhead door headers. Support the headers with at least two trimmer studs on both ends. Double the top plates on the wall section by attaching 2-inch by 4-inch boards. Sheath all of the wall sections with plywood.

Roof

• Construct the roof with prefabricated roof trusses. Place the trusses 24 inches on center. Sheathe the roof with plywood. Apply roofing felt and cover with shingles.

Finishing

• Install insulation and other finishing products according to the manufacturer's specifications.