How to Build Deck Stairs: A Complete Step-by-Step Guide

Building deck stairs is one of the most rewarding DIY projects you can tackle. Whether you're adding stairs to a new deck or replacing worn-out ones, this guide walks you through every step of the process.

Planning Your Deck Stairs

Before you pick up a saw, careful planning is essential. You'll need to determine the total rise (the vertical distance from the ground to the deck surface) and decide on the number of steps.

Measuring Total Rise

Use a straight board and a level to measure from the deck surface straight down to the landing area. This measurement is your total rise - the most critical number in stair construction.

Calculating Rise and Run

The ideal riser height is between 7 and 7¾ inches per the IRC (International Residential Code). Divide your total rise by your target riser height to find the number of steps. For example:

• Total rise: 48 inches
• Target riser height: 7.5 inches
• Number of steps: 48 ÷ 7.5 ≈ 6 steps (actual rise = 8 inches per step)

Tools You'll Need

• Framing square with stair gauges
• Circular saw
• Jigsaw or handsaw (for finishing cuts)
• Level (4-foot)
• Tape measure
• Drill/driver
• Speed square
• Pencil

Choosing Materials

For outdoor deck stairs, pressure-treated lumber is the standard choice. You'll need:

• Stringers: 2×12 boards (one for every 16 inches of stair width, minimum 3)
• Treads: 2×6 or 5/4×6 deck boards (two per step for standard width)
• Hardware: Structural screws, stair angles or joist hangers, concrete for footings

Cutting Stringers

Mark your framing square with stair gauges at the rise and run measurements. Starting from one end of the 2×12:

1. Align the gauges with the board edge
2. Mark the rise and run
3. Slide the square and repeat for each step
4. Cut along the marks with a circular saw
5. Finish inside corners with a jigsaw

Pro tip: Cut one stringer first and use it as a template for the rest. Always verify your first stringer before cutting others.

Installing the Stairs

1. Set footings: Pour concrete pads at the base where stringers will rest
2. Attach stringers to deck: Use joist hangers or a ledger board
3. Install treads: Screw treads to stringers with 3-inch deck screws, leaving 1/8-inch gaps for drainage
4. Add risers (optional): Enclose the risers for a finished look

Building Code Requirements

Per the IRC for residential deck stairs:

• Maximum riser height: 7¾ inches
• Minimum tread depth: 10 inches
• Minimum stair width: 36 inches
• Handrails required if 4 or more risers
• Riser height variation: no more than 3/8 inch between any two risers

Common Mistakes to Avoid

• Not accounting for the ground-level step (the ground itself is the last "tread")
• Forgetting to subtract tread thickness from the top riser
• Using undersized lumber for stringers
• Skipping the concrete footing at the base

Following these steps and your local building codes will result in safe, durable deck stairs that will last for years.