How to Plan Stairs

Stairs are handy in most situations where you want to go from one height to another. Knowing how to build stairs is useful not only for connecting the main floor to the basement or attic, but also when you install a deck or above-ground pool, or build a stage to present a play or make a speech. There are three main parts of a stairway: the risers, which go vertically; the treads, which go horizontally; and the stringers, which are the supports. Some stairways are open stairs that don't have risers. Open stairs provide more toe space for climbing the stairs, especially if the treads are shallower than normal.

Measuring tape
Graph paper
pencil
Calculator

Instructions

- 1
  Check your local code for rules on rise and run sizes and use these regulations to calculate your stairs.
- 2
  Measure the height that the stairs must span. Because you normally can't reduce the height the stairs have to span, this is the controlling measurement. Draw the height on graph paper to help you visualize the stairs.
- 3
  Divide the height in inches by 7 1/2 and subtract 1. This is the number of steps you will need to build.
- 4
  Multiply the number of steps by 11 inches; this is the distance that your stairway will span.
- 5
  Add up to 3/4 inch to the bottom stair if the height does not divide evenly by 7 1/2. To make up any additional height, plan to build a bottom landing pad. Landing pads are larger than stairs to allow for stopping and reorienting to the unusual height of the final step. Plan for a 3-by-4-foot landing at the least; 1 foot will extend under the stair stringer.
- 6
  Plan the width of your stairs. Stairs wider than 3 feet require a third notched stringer in the middle of the stairs for support.
- 7
  Multiply the number of stairs by the width of the stairs; this is how many board feet of 12-inch wood you will need for the steps. Multiply the number of rises by the width of the stairs to determine how many board feet of 7 1/2-inch riser you will need. To calculate how long a stringer you will need, square the height and the length of the stairs and add these numbers together; take the square root of the result.

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