When building deck stairs, everything starts with the stringer layout.

A stair stringer is the structural support that holds each step in place. If the layout is incorrect, the stairs can feel uneven, look unprofessional, and even become unsafe. A correct layout ensures a smooth installation and a solid, long-lasting result.

Step 1: Calculate Total Rise and Run

Before marking the stringer, you need two key measurements.

Total rise is the vertical height from the ground to the top of the deck.
Total run is the horizontal distance the stairs will cover.

These measurements determine the number of steps and the overall layout.

Typical residential standards:

• Riser height: 175–195 mm
• Tread depth: 250–280 mm

To calculate:

• Number of steps = Total rise ÷ riser height
• Total run = Number of steps × tread depth

Step 2: Choose the Stair Style

There are two main types of stringers.

Open (notched) stringer
This is the most common type for decking. It has a visible zig-zag pattern and is easier to build.

Closed stringer
This provides a cleaner appearance but is more complex to construct.

For most residential outdoor decks, open stringers are the practical choice.

Step 3: Mark the Stringer

Accurate marking is the most critical step.

You will need:

• Framing square
• Pencil
• Stair gauges (optional but recommended)
• Timber board (commonly 2×12)

Set the rise and run measurements on the framing square. Place the square on the edge of the timber and draw the first step. Slide the square down and repeat the process for each step.

You are repeating the same triangle pattern consistently along the board.

Step 4: Adjust the Top and Bottom

This is a detail many beginners miss.

Bottom adjustment
The bottom of the stringer must be reduced by the thickness of the decking board. This ensures that all steps are the same height.

Top connection
The top of the stringer should align cleanly with the deck frame and landing surface.

Without these adjustments, the first or last step may feel uneven.

Step 5: Cut the Stringer

Use a circular saw for straight cuts and a jigsaw to finish the corners.

Avoid cutting past the marked lines, as overcutting weakens the structure.

Clean, accurate cuts will improve both strength and appearance.

Step 6: Test Before Repeating

Always test one stringer before cutting the rest.

Check:

• Step height consistency
• Level treads
• Proper fit to the deck

Once confirmed, use this first stringer as a template.

Step 7: Install Multiple Stringers

Deck stairs require multiple stringers for support.

Typical spacing:

• 300–400 mm apart

Wider stairs require more stringers to prevent flex and ensure stability.

Spacing should also match the requirements of your decking boards.

Common Mistakes to Avoid

• Inconsistent rise heights
• Incorrect bottom cut
• Too few stringers
• Ignoring the decking thickness
• Overcutting the corners

These mistakes often lead to structural issues and poor finish.

Practical Tips

• Use straight, dry timber
• Apply joist tape to protect stringers from moisture
• Plan the tread layout based on the decking board width
• Double-check all measurements before cutting

How This Affects Decking Installation

Stair design must align with the decking layout.

For example, tread depth is often determined by:

• Deck board width
• Gap spacing

If not planned properly, boards may not fit evenly, resulting in unnecessary cuts and wasted material.

PureSolid Insight

A well-built stair system is part of a larger structure.

For best results, think in terms of a complete system:

• Composite decking
• Proper subframe
• Correctly spaced stringers

This approach ensures long-term performance, not just a visually acceptable result.

FAQ

What timber is used for stair stringers?
Typically, 2×12 treated timber.

How far apart should stringers be?
Usually 300–400 mm, depending on decking type.

Can composite boards be used as stringers?
No. Structural elements should be timber or steel.

How do I confirm my layout is correct?
Test one stringer before cutting the rest.

Final Thoughts

Stair stringer layout is a precise but straightforward process.

Getting it right ensures safe, stable and professional-looking stairs. It also makes the rest of the installation much easier.

When combined with a properly designed decking system, it contributes to a durable and high-quality outdoor space.