How to Build Under-stair Basement Storage Shelves

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The boxes shown fit under a staircase with a 45-degree pitch: For every 12 inches the stairs rise, they run (travel horizontally) 12 inches. The boxes step up and over in 12-inch increments.

If your stair slope is more gradual, your boxes will need to be wider to fit; more steep and the boxes will be narrower. To find out, hold a tape measure vertically with the hook on the floor. Move the tape along the bottom of the stair until the distance to the floor is 36 inches. Use a 4-foot level to make sure the tape is plumb, then mark the point on the floor. Measure from the floor mark to the point where the bottom of the stair meets the floor. Let's say the distance is 46 inches. Divide 46 by 3 to get 15-5/16 inches. Now you know your small boxes and tall box need to be 15-5/16 inches wide while your large boxes should be 30-5/8 inches wide.

Use a circular saw and straightedge jig to crosscut one 3/4-inch-thick particleboard sheet to 70-1/2 inches long -- the length of the tall box sides (H).

Although the lengths of the three backs (C) add up to 72 inches, you need a little more length to allow for the kerfs -- the 1/8 inch of material that the saw blade turns into dust with each cut. Snap a line at 72-1/2 inches across the 1/2-inch-thick particleboard sheet. Make a freehand cut with a circular saw.

Rip all four particleboard sheets to make eight pieces 23-7/8 inches long. Rip-cut the particleboard on the tablesaw, and have someone support the sheet at the back of the saw table. Or use a circular saw and an 8-foot-long straightedge jig.

Use a circular saw with a straightedge jig to make all the cuts that go completely across the ripped pieces (see the cutting diagrams). These are parts A, B, and C, and the cuts that will separate parts D from parts E. Label all parts as you cut them.

If you have a tablesaw, set the rip fence to 11-7/8 inches. Cut the remaining 3/4-inch-thick pieces (D, E, G). Leave the fence setting at 11-7/8 inches. If you don't have a tablesaw, make these cuts with your circular saw and straightedge jig.

Rip-cut one long piece of 1/2-inch particleboard into two 11-7/8-inch-wide pieces. With your circular saw and straightedge jig, crosscut one of these pieces to 72 inches to make the back (I) of the tall box. Cut three 12-inch backs (F) for the small shelves from the other 11-7/8-inch piece.

If you don't need tall storage, consider adding shelves to the tall box. Just rip the whole panel used to make the sides (H) into two 23-7/8-inch pieces. Cut the sides to length, then use the offcuts to make up to four shelves.

Lay the tall box sides (H) next to each other, with edges flush. Draw lines across both pieces with a framing square to show where to locate the bottom of the shelves. Extend these lines across the outsides of the panels so you will see where to drive screws.

Attach the shelves before you attach the top and bottom pieces. Have someone hold each shelf along the layout line as you glue and screw the shelf to one side. Then glue and screw the other side in place.

Assembly is the same for large and small boxes. Apply glue to the top edge of one box side (B or E). Use a bench vise or clamps to hold the piece, glued edge up. Screw the top (A or D) to the side, using three screws for small boxes and five screws for large boxes.

Apply glue to the top edge of the other box side. Put the top in place, make sure the edges are flush, then screw it in place, again with three screws for small boxes, five screws for large boxes.

Turn the box over and apply glue to the bottom edges of both sides. Put the bottom (A or D) in place, check that the edges are flush, and secure with three or five screws into each side.

The back piece keeps the box square, so be sure to put backs on before glue sets. Lay the box on its face and screw the back in place -- five screws per edge for large boxes, three screws per edge for small boxes.

Apply glue to the top edge of a long side (H), and place the piece flat on a workbench. Put the top (G) in place and make sure it is flush to the front and back of the side. Attach with five screws. Do the same for the bottom (G).

Turn over the long box assembly, apply glue to the top and bottom edges of the second side, and screw it into place between the top and bottom. Finally, screw the back in place using 12 screws along each side, five screws across the top and five screws across the bottom.