Composite Decking Corner Trim Installation: Step-by-Step Guide
Corner trims are a finishing detail that give your deck a polished, professional appearance. Corner trims neatly conceal board ends, protect exposed edges and ensuring the system is visually consistent.
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Thu, 28 Jul 2026
This decking corner trim installation guide explains how to fit trims for a flawless finish that lasts for years.
Why Use Decking Corner Trims?
Corner trims (sometimes called L-profiles or angle trims) serve both decorative and functional purposes:
Edge protection: Shields exposed board edges.
Aesthetic appeal: Creates continuous edges along fascias and steps.
Durability: Reduces water ingress on composite decks.
When correctly installed, corner trims provide a professional architectural finish that complements the colour and texture of the main decking boards.
How to Install Composite Decking Corner Trims
Corner trim can be used with fascia to cover exposed board sides and substructure. A corner trim is an L-shaped profile that sits on the corner of the deck edge to provide a capping.
Installing corner trim results in visible screws. If you are concerned about visible screws you can get coloured screws to make them less visible. We offer colour-matched screws for our EnviroBuild decking products.
Step 1 - Measure and Mitre
Measure the required amount of corner trim and cut down to size, mitre down the ends at 45° angles if installing around corners.
Step 2 - Place the Corner Trim
Cover the deck edge with corner trim.
Step 3 - Fix the Corner Trim
Pre-drill 4mm countersunk pilot holes, then fix with 50mm countersunk screws.
Do not overdrive screws when through composite products, finish tightening by hand.
Corner trims should only be screwed into the deck.
It is not recommended to attach the trim using glue.
Expansion gaps
Ensure you have left appropriate expansion gaps where corner trim ends meet (minimum 0.2% of the board length).
Common Mistakes to Avoid
Cutting trims too short or at incorrect angles.
Over-tightening screws, leading to stress.
Skipping expansion gaps.
Avoiding these ensures your deck edge looks professional and performs reliably year-round.
A Polished Deck Finish
Installing corner trims is the final step that perfects your decking project. They provide protection and a refined aesthetic, turning exposed edges into elegant finishing details.
EnviroBuild offers a full range of composite decking trims, fascias and corner profiles, designed for quick installation, consistent colour matching and long-term weather resistance.
