The area under a stair unit often goes to waste. Instead of stacking boxes, storing disorganised items or looking at empty unused space, create an under-the-stair shelving unit. Under stair shelving works well to store shoes, sporting equipment, and other household items. If you have a playroom with stairs, you may wish to use this shelf unit to hold toys. Building an under-stairs shelving unit does not require extensive skill. Instead, you need basic carpentry skills and tools.
Place a piece of plywood against the stairway, while resting the plywood on top of a 5 by 10 cm (2-by-4-inch) piece of timber. Mark the edges of the plywood level with the stair riser using a pencil; this transfers the angle of the stairs on to the piece of plywood. Place a chalk line from mark to mark on the plywood, snap the chalk line to make the mark on the plywood. Repeat for other backing pieces.
Place the plywood on a flat level surface, and cut the chalk line mark with a circular saw. This creates the back piece of the shelving unit. Repeat for all plywood backing pieces.
Test to verify the backing pieces fit into place by sliding them under the stairs with your hands. If they do not fit, measure the difference and adjust the plywood with your circular saw.
Lay the plywood pieces down on a flat, sturdy work surface, such as a floor and draw layout lines for shelves. As you draw the mark lines for the shelving, add 1.9 cm (3/4-inch) onto the next shelf upward. This creates a step-up in the shelving, allowing you to fasten the shelves through the sides. Cut the shelves out with a circular saw. The width varies depending upon your personal preference. Cut risers to go in between each row of shelves. Risers fasten from the bottom to the top of the stair risers in each section of shelves.
Cut two pieces of 5 by 10 cm (2-by-4-inch) timber to fit along the bottom of the shelf system. This allows you to secure the shelving unit from the bottom, preventing you from drilling through the floor.
Flush the two back pieces so they create an L-shape. Use two screws, fasten the plywood on the corner, and fasten the remaining plywood by inserting screws approximately every 20 cm (8 inches) with your drill.
Place the shelves and uprights on the back pieces to the previously marked layouts. Fasten the shelves and uprights through the backing piece every few inches while checking for levelness using a carpenter's square. Secure all shelves and risers in this manner. Continually check for all levelness while working. Verify no pieces extend beyond the backing.
Slide the assembled unit under the stairs and fasten the shelf edge to the bottom of the stair stringers with screws and a drill.