Chipboard is more commonly called OSB, or oriented stranded board. Chunks of wood are laminated together and formed into sheets to make this building material. It is commonly used for roof sheathing, exterior wall sheathing, and for subflooring. Building codes dictate the correct thickness when using OSB as a subfloor material, so check with your local building inspector before you begin the installation.
Lay out sheets of OSB so they span at least two joist supports. Trim the OSB to fit if needed by marking the boards with a straight edge and a pencil; cut the sheets with a circular saw. Lay the sheets in place over the joists with the "This side down" label oriented correctly.
Hammer the sheets of OSB to the joists using 2 3/8-inch ring shank nails every 8 to 12 inches.
Space each subsequent sheet of OSB 1/8-inch away from other sheets for expansion purposes. Offset the ends of each sheet 1/3 the length of the sheet so the seams do not line up. This will increase structural integrity.