If your shed could benefit from a bit more space in which to store things, consider adding wood shelves. These add additional room and make items such as tools easier to access. Adding just one or two shelves around the inside of the shed can almost double the space you have for storage.
Measure the area where you want to build the shelves in your shed. Calculate the length of the shelves and the width you want. Use the exposed studs in the shed to support the shelves on three sides and one board as the outside corner support. Measure from the corner to the inside of the stud closest to the length of the shelves that you desire. Measure out from the corner to the outside of the stud closest in distance to your desired width.
Calculate the height from the floor to the ceiling. Adjust that height by subtracting 3 1/2 inches for the bottom plywood support, and 3 to 4 inches at the bottom to keep the shelves off the floor. Decide on the height of each shelf, and add three-quarters of an inch for the thickness of the plywood. Divide your space by the height of each shelf and calculate the number of shelves.
Add the length of the shelves to the width. Multiply that number by 2 and then by the number of shelves you need. Multiply the number of shelves by 6 inches and add that to your answer. Divide that number by 12 to find the number of lineal feet of 2-by-4 wood you need. Get an additional piece of 2-by-4 wood long enough for the height of the outside corner support board. Shelf plywood comes in 4-feet-by-8-feet sheets. Use a three-quarter-inch sheet for strength. Calculate the number of sheets you need.
Build the outside side support. Use the plywood for the height and mark a spot 3 to 4 inches from the floor. Place a board that's cut the width of the shelves on top of the support board, with the right edge even with the right edge of the corner support. Predrill 4 holes equal distances where the boards overlap and screw them together.
Figure out where you want the next shelf by adding three-quarters of an inch to the height of the shelf and measuring that distance from the top of the attached board. Make a mark. You'll line up the top of the next 2-by-4 to this mark. Continue until you have enough boards for the number of shelves attached to the corner support board. It should look like a ladder with one side missing with the rungs the shelf supports.
Attach the outside corner framework by standing the corner support board and connecting the other end of the shelf support board to the inside of the stud designated as the length. Hold them in place with clamps until you attach all of the boards. Clamp a board to the corner support for the length of the shelves and to the stud on the opposite side for the front shelf support. Predrill and screw it down to both the stud and corner support. Do this for every shelf.
Screw on boards that support the shelves from the corner and butt them up to the ones in front. Screw them down. Measure the distance between the side boards at the back and cut enough boards for the shelves. Screw these in place so you now have a platform to set the plywood shelving. Cut the shelving to size and screw it in place. Your wood shelves for your shed are complete.