Construction of a heavy duty storage cabinet is a fairly simple process. Below is a rough outline of how to go about construction, which can be modified to fit your needs.
Step 1 – Add the Shelves First
Start by measuring out the “footprint” for your cabinet, to get an idea of how big your shelves will be. To save cost and time, by ½” plywood for your shelves and base your shelf size off the size of the strips of plywood. Once you know the size of your shelves, use 2x3’s or 2x4’s to construct a shelf frame to length and width, screwed together with heavy duty L shaped brackets.
Add a couple cross beams across the center for extra support, then nail your plywood on top. Repeat this process for however many shelves you desire.
Step 2 – Attach the Upright Fixtures
Attach your uprights to the corners of your bottom shelf, either on the short side or the long side of your shelf. If placed on the short side, then the back of the shelf can be placed right against the wall (or even screwed into it, saving on rear uprights) to save on lumber. If your floor is uneven, or regularly gets wet, feel free to raise the bottom shelf several inches.
For remaining shelves, measure out on each upright where you want that shelf to sit, and clamp a block of wood in the desired place. Use a level to make sure each piece is even, then screw it into the uprights. You can then lay your next shelf on top. If it still sits level, screw the shelf itself into the uprights for extra support. Repeat for each set of shelves desired.
Step 3 – Add the Sides and Cabinet Doors
If you want to enclose your shelves, you need only nail more plywood to the sides and the back. For cabinet doors, cut plywood (or other lumber, if you wish) to size and attach with hinges. Cut grooves on the outside of each cabinet door opposite the side from the hinges to make basic door handles, or buy door handles from your local hardware store.