How to Build Deck Stairs

Building your own deck stairs is a challenging project. You need to make perfect calculations of the stairs’ height. You wouldn’t want anyone falling from your stairs!

The parts of the stairs which show are the risers, treads or steps, and the baseboard or skirt which hide the unsightly notched stringers and reinforce them as well. The notched stringers hold the risers and treads underneath.

Materials needed

  • Wood – the parts that show should match what was used in your deck
  • Pressure-treated – 2×12 commonly used for stringers
  • Three treated 2x10s, two 2x12s and two 2x4s and a 6-foot 2×6
  • 3 D galvanized nails for fastening risers to the stringers
  • 2×4 nails for reinforcement
  • 3-in deck screws for fastening the baseboard and treads to the stringer

Tools needed

  • Carpenter’s Square
  • Set of Stair Gauges
  • 4-ft. level
  • Tape measure
  • Calculator
  • Circular saw
  • Handsaw

Steps to Build Deck Stairs

Before construction work, check the building code for required measurements for safe stair design.

Drawing a sketch of your plan will help you to execute it properly. Your measurements must be finished before you start cutting the first plank.

You begin by determining the total height Y that your stairs need to have. You calculate Y by estimating where the last step will fall using a 40-degree slope. Rest a straight board on the deck and level over to that spot and measure down to the ground.

To get the number of steps: divide Y by 7 (the usual riser or step height). Round off if your answer is a decimal (up if the remainder is .5 or above, and down if it’s less than 0.5). The building code recommends that the height of a riser should be between 6 ½ and 8 inches.

To get the number of tread steps, subtract one from the number of risers. Multiply the answer by 10.25 inches to get the length of the tread.

Determine how thick the stair tread material is. This is usually one inch, the thickness of 5/4×6 deck boards. Remember to deduct the thickness of the step and any additions from the length of the stringer (the board to which you fasten your riser).

When you have finished your calculations, you are ready to cut your wood boards. Fitting the risers and treads to the stringers should be easy if you made the right computations.

You also need to cut one right and one left board for your base (also called the skirt of the stairs). It is good to have a solid base at the landing point. It could be a small concrete slab, a small wooden deck or a gravel base.

Adding joist to the staircase will make it stronger. Putting in railings will also provide additional safety to the climbers.