Making your own plans for your outdoor wooden storage box enables you to tailor the size of the box to the items you intend to store in it. It will be easier to choose the correct materials and fasteners when you know ahead of time whether the box needs to open even with the ground or can be lidded.
Assemble all of the items you need to store outdoors. Measure each item and create a chart or list of the total height and floor space that you will need. Determine whether the storage box will have any compartments or shelves to maximise space and minimise contact between stored items.
Determine whether items will be rolled, pulled or driven into the storage box or whether they are small enough to be hung or placed by hand instead. If the majority of the items will need to be rolled, pushed or driven inside, the box should open from one side or along its bottom front edge.
Make a three-dimensional rough sketch with the total length, depth and height needed marked clearly on the diagram. This does not have to be architect or draftsman-quality. It is just a guide for your own purposes.
Mark positions of hinges, locks, knobs and handles on your sketch. Use curved arrows to indicate which direction hinges will open.
Determine what materials you will use to build the box. If you decide to use planed timber instead of cheaper options such as plywood, indicate how many full-length stock timber pieces you will need. For example, a storage box 1.2 by 2.4 by 1.2 m (4 by 8 by 4 feet) can be made from five sheets of plywood. To make that same box from stock lumber, you would need 20 2.4 m (8 foot) 2.5 by 30 cm (1 by 12 inch) boards.
Indicate what type of joinery you will use. Box corners can be butted, mitred, mortised or dovetailed. Different types of joinery may result in a need for additional materials. Rockler Woodworking and Hardware (see Resources) offers an excellent explanation of mitring tools and terminology.
Create template for any special pieces. This includes pieces with curves or angles or anything that cannot be made by cutting a standard board in halves, quarters or eighths.
Make a mockup of your box using your final plan, using the cheapest materials possible. This ensures that all measurements are correct, all needed angles will fit together and provides a chance to make any design alterations needed without an expensive outlay.
Use your plans to make your intended final product.
Once the box passes the 1.8 by 2.4 by 1.5 m (6 by 8 by 5 feet) mark, it ceases to be a box and is either a storage unit or a shed, depending whether it is a free-standing structure with a roof.