To build a garage closet, you’ll use the same basic steps you’d use for a closet in the house, with a few exceptions.
Step 1 - Plan and Measure
It is often easiest to build a closet in a corner, since there are already two walls to use, which simplifies construction.
Other considerations for location are to look at the flow of traffic through the garage and where the doors will open.
Measure carefully and determine how large the closet will be. Mark the area on the floor with masking tape.
Step 2 - Frame the Walls
Beginning with the bottom frame, cut pieces of 2x4 to the exact width you want the closet to be. Square and secure to the floor with masonry screws. Put the board in place for the length of the closet. Square and screw it down. Repeat as necessary if you don’t have walls on the remaining sides.
Frame the walls of the closet, leaving a space for the door, and raise them. Attach to the bottom frame.
Step 3 - Attach Wall Board
Put drywall (or paneling, etc.) around the framed closet. Finish as necessary. Finally, install the door, if you will have a door on the garage closet.