Box springs from larger beds such as queen- and king-sized beds may not fit up older staircases. This is especially true if the staircase is angled. While most mattresses are easily bendable, a box spring is composed of a solid wooden frame that will not bend to go up the stairs. To make the box spring fit, you will have to make cuts in the wooden frame and bend the box spring in half. You can then carry it up the stairs.
Lay a clean plastic tarp over a flat surface. Lay the box spring on the tarp, upside down, so the fabric underside faces you.
Cut through the fabric cover in the middle of the box spring, across the width of the box spring, not the length. Make the cut where the cover is between two horizontal slats.
Cut the fabric on both sides of the box spring, following the lines of the original cut you already made. Cut all the way down to the floor, or the face of the top of the box spring.
Use a handsaw to cut all the way through the center vertical slat, making the cut through the slice in the fabric. Cut the framing slats on each side of the box spring, under the cuts into the side fabric you already made.
Turn the box spring on its side. Place the middle of the front of the box spring against a wall. Have a helper bend one side in toward the wall while you bend the other side, folding the box spring in half.
Pull the box spring off the wall, keeping it folded in half as much as possible. You can now carry the box spring up the stairs. Once you get it in place, use wood glue to glue the slats back together or leave them. The box spring will still work properly.