To build heavy-duty storage shelves, find the wall studs, determine the dimensions of the shelves, and mark their locations on the walls. Install the ledger boards of the shelves and all the supporting hardware, and secure the transverse support boards in place. Place the main horizontal boards, and put in the front legs for extra support.
It is best to attach the shelves to the studs in the walls, as they are the most secure areas. You can find the studs using a stud finder. Use 2-by-12-inch boards for the main parts of the shelves, and cut them if they are too wide. Make sure that all the components are leveled when installing them.
Make ledger boards out of 2-by-4-inch boards that are 4 feet long, and secure them to the walls using three wood screws per board per stud. Attach a joist hanger in the middle and at the ends of each board. Make transverse support boards out of 2-by-4-inch boards that are 12 inches long, and attach them to the joist hangers using standard screws. Make sure to attach the flat horizontal shelves to the transverse beams and to the ledger boards using wood screws. Make front legs out of 4-by-4-inch boards that measure 8 feet long, and attach them on each side of the shelves using wood screws.