How to Build Deck Stair Stringers

Written by shelly schumacher
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Stair stringers are the long boards underneath the stair treads that provide stability for the staircase. In a normal-width staircase there are typically three stringers, one on each side of the stair tread and one in the middle. Building the stringer correctly is crucial to having a safe staircase as well as one that will pass local building codes. Building a stair stringer can be a bit difficult, as it requires precise measurements and a few specialised tools.

Skill level:
Moderately Challenging

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Things you need

  • Tape measure
  • Pencil
  • Framing square
  • Stair calculator
  • Circular saw
  • Hand saw
  • Level
  • Saw horses
  • Pressure-treated 2-by-12-inch stringer board

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  1. 1

    Measure from the top of the stairs to the ground below the deck edge. This will provide the deck height measurement.

  2. 2

    Decide the rise or height you would like to have for the steps. The maximum allowable rise by most building codes is 7 3/4 inches and the suggested minimum is 4 inches.

  3. 3

    Determine the desired run, or depth, of each stair tread. The minimum run for most building codes is 10 inches.

  4. 4

    Input your desired rise and run as well as the total deck height into a stair calculator. The calculator will determine how many steps should be on the stringer as well as the cutting angle.

  5. 5

    Mark the 2-by-12-inch stringer board with pencil and framing square, using the measurements and angle from the calculator. Start by marking the bottom stair measurements and work toward the top stairs.

  6. 6

    Cut the marked 2-by-12 stringer board with a circular saw at the pencil line. Use a hand saw to make finishing cuts in the corners.

  7. 7

    Place the bottom of stringer on the stair landing and move toward the deck edge. Hold a level across the stringer to determine it the cuts are square and the fit is good. If not, adjust as necessary by recutting.

  8. 8

    Place the first cut stringer on top of the remaining 2-by-12 stringer boards. Use as a template to trace the stair pattern onto the boards.

  9. 9

    Cut the remaining stringer boards as noted in step 7.

Tips and warnings

  • Never space stringers more than 16 inches apart.
  • Place stringers on saw horses to make cutting easier.
  • Always use 2-by-12 pressure-treated material.
  • Always wear safety glasses when cutting wood.
  • Use power tools with caution.

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