How to Carpet a Spiral Stair Case

Measure the size and shape of each step. Though the steps have slight curves, measure a straight line from the top right corner to the top left corner. Then measure the horizontal distance between the bottom corners. Measure the vertical distances between the corners on the left and right sides. Despite the curvature of the step, the step should be the same width from top to bottom.

Use your tape measure to determine how much space you want on either side of the carpet when it is on your stairs. Subtract this measurement from the measurement for your step width, then use a sharp utility knife to cut out a piece of carpet in the size of your step. Divide the difference between the step width and the carpet width by two, then measure in from either side of the step by that amount and mark it with a pencil -- this is where the carpet lines up.

Place your cut-out piece of carpet on the step. Unlike the step, which has curves, the cutout should have sharp angles. Flip the carpet over so that the bottom faces up, and use a marker to trace the curvature of the step onto the carpet. Cut along this line with your utility knife to make a carpet cutout that lines up with the curvature of the step.

Lay your carpet cutout on top of a piece of carpet pad and trace the outline. Remove the cutout, then measure 1 inch in from all sides and draw new lines. The result should be an outline that is the same shape as the cutout, but 1 inch smaller on every side.

Center the carpet pad on the step and staple it in place with a staple gun. "This Old House" recommends using 9/16-inch staples every 3 inches.

Center your carpet cutout over the carpet pad and the step. Staple it in place along the edges, stapling into the step, not the carpet pad. Repeat this process for every step in your staircase.