How to Install Decking Edge Boards: A Step-by-Step Guide

A beautifully finished deck doesn’t just depend on straight board lines and a solid frame — the edges and perimeter details make a significant difference in appearance, durability, and overall quality.

Edge boards — also called deck edge trims — are composite boards installed along the outer edge of a deck to conceal cut ends, protect edges from wear, and give your outdoor space a clean, professional finish.

At PureSolid, we emphasise finishing details like edge boards because they elevate both the visual quality and performance of your deck’s perimeter.

What Is a Decking Edge Board and Why Use It?

A decking edge board is a flat board installed horizontally along the outer edge of decking boards. It serves several purposes:

• Conceals raw board ends for a polished, architectural look

• Protects deck edges from moisture, knocks, and abrasion

• Defines steps, raised areas, and perimeter borders

• Improves overall visual cohesion of the decking surface

Edge boards work seamlessly with hidden fastening systems to achieve a flush, modern finish that enhances your outdoor space.

Planning Before You Start

Before installing edge boards, homeowners should:

• Confirm the deck layout and joist positions

• Allow for expansion gaps between boards

• Choose the edge board profile that matches the decking style

• Select compatible fasteners (hidden clips or starter clips)

Important: Always plan for expansion gaps between edge-board butt joints — a minimum of 6 mm (0.2 % of the board length) — to accommodate seasonal temperature changes.

Two Methods of Installing Edge Boards

Depending on how your deck runs, edge boards can be installed parallel or perpendicular to the direction of the decking.

👉 Parallel Edge Board Installation

1. Mitre the ends at corners
   Cut the ends of edge boards to 45° mitres where corners meet.

2. Secure the board to the joists
   Place the edge board over the outer joist edge and use hidden fasteners at approx. 300 mm centres.

   • If using a matching fascia board, use 6 mm or 3 mm hidden fasteners at the bottom.

   • If no fascia is planned, you can start with starter fasteners at the bottom edge.

3. Align and clip first decking board
   With the edge board lightly secured, slide the first decking board into the hidden fasteners.

4. Fully tighten fasteners
   Once the next decking board is in place, tighten the clips fully to lock everything in position.

👉 Perpendicular Edge Board Installation

1. Mitre the ends at corners
   As with the parallel method, mitre the board ends for clean corner joins.

2. Install starter clips
   Clip starter fasteners on the top side of the outer joist at about 300 mm spacing. The vertical clip edge should be ~35 mm from the joist edge.

3. Insert the edge board into the clips
   Push the edge board down into the starter clips until fully seated.

4. Secure the bottom edge
   Use 3 mm or 6 mm hidden fasteners to secure the bottom edge board to the joist.

   • Lightly fix if a fascia board will be added later.

   • Fully tighten once the fascia or decking boards are in place.

Common Mistakes to Avoid

A professional finish depends on careful execution. Homeowners and builders often make the following mistakes:

• Over-tightening screws, which can distort boards or clips

• Cutting boards without precise mitres, leading to visible gaps

• Forgetting expansion gaps, which causes buckling due to temperature changes

• Misaligning trims or fascia boards, resulting in uneven edges

Avoiding these errors ensures your deck edge looks consistent and durable for the long term.

Pro Tips for a Seamless Finish

✔ Always measure twice before cutting
✔ Use recommended fasteners that are corrosion-resistant
✔ Leave at least 6 mm gap between edge board butt joints
✔ For steps or raised platforms, ensure edge boards are adequately supported

Attention to these details avoids common issues and creates a professional-looking deck edge that complements the entire space.

Frequently Asked Questions

Do I always need edge boards on a deck?
Not always, but edge boards significantly improve aesthetics and edge protection, especially where decking boards end or steps are present.

Can I use regular decking boards as edge boards?
Yes, in some systems you can use regular decking boards for edge trim, but using purpose-designed edge boards gives a better finish and fit.

Why are expansion gaps important?
Composite boards expand and contract with temperature changes. Small gaps (e.g. 6 mm) prevent buckling or board deformation.

What fasteners are best for edge boards?
Hidden fasteners (e.g., 3 mm or 6 mm clips) are commonly used for a clean, clip-in finish that keeps screws concealed.

Final Thoughts: Complete the Look

Installing decking edge boards is more than just a finishing step — it’s a design detail that defines the quality of your outdoor space. A clean edge not only enhances the visual appearance but also improves edge protection and long-term performance.

At PureSolid, we recommend incorporating edge treatments into your decking plan from the beginning. This helps ensure:

• Consistent colour match between boards

• Flush alignment with decking finishes

• Professional perimeter that resists weather and wear

A well-installed edge board turns a good deck into a great one — elevating both function and style.