Freight is calculated based on your location and order size.We'll contact you with a freight cost within 1 business day before processing payment.
The corner of a retaining wall is its most structurally complex point: two wall runs meeting at 90°, with soil pressure acting from two directions simultaneously. The 90° corner post handles that load. The corner post cap protects it. Precision-formed to fit the compound profile of a 90° corner post fabricated from 100PFC C-channel, this galvanised steel cap seals the post top against water, debris, and corrosion, preserving the structural integrity of the most load-critical post in the wall.
Corner posts are often the last thing people think about when ordering accessories, and the first thing that causes problems when left uncapped. Water sitting in a corner post cavity has nowhere to drain: the compound section traps it. In coastal and high-rainfall areas, an uncapped corner post can show visible internal corrosion within 12–18 months.
Specified and supplied by the Retaining Walls Direct trade team. Last updated August 2026.
The Galvanised Steel 90° Corner Post is fabricated by welding two 100PFC C-channel sections at a right angle, creating a post that captures sleepers running in two perpendicular directions. This compound section profile means the post top has a more complex shape than a standard end post or middle post, and requires a cap specifically profiled to match. A standard C post cap or H post cap will not fit correctly on a corner post.
| Post Type | Section | Compatible Cap |
|---|---|---|
| 90° Corner Post | 100PFC (compound) | ✅ This product |
| H-Beam Middle Post | 100UC | H Post Cap |
| C-Channel End Post | 100PFC | C Post Cap |
| 45° Angle Post | 100PFC (compound) | Contact us, different profile |
The 90° corner post has a compound cross-section: two C-channels welded at right angles. This creates a post top with four open faces rather than two. A standard C post cap covers only one channel face and leaves the perpendicular face exposed. The 90° corner post cap is specifically profiled to cover the full compound section, sealing all open faces simultaneously. Using the wrong cap leaves part of the post cavity exposed, which defeats the purpose entirely.
Corner post caps are tool-free to install. Once your corner post is cut to final height and the top sleeper courses on both wall runs are in place, press the cap firmly over the compound post top. Ensure the cap seats fully on all faces before applying pressure: the compound profile requires correct alignment before the friction fit engages.
For permanent installation in coastal, high-wind, or high-humidity environments, apply a bead of construction adhesive around the inside perimeter of the cap before fitting. This creates a weatherproof bond that will outlast the wall.
Install caps last, after all sleepers on both wall runs are placed, drainage is complete, and backfill is finished. Corner caps are particularly vulnerable to being dislodged during compaction due to their exposed position at the wall corner.
No. A standard C post cap is profiled for a single 100PFC channel face and will not cover the compound section of a 90° corner post. Using the wrong cap leaves part of the post cavity exposed. Always use the cap specifically designed for the post type.
Yes. Even if the corner post is partially obscured by a fence or adjacent structure, the post top is still exposed to water running off the top sleeper course. The cavity will still collect water and corrode from the inside regardless of what surrounds it at ground level.
One cap per 90° corner post. Count the number of right-angle changes of direction in your wall layout: each requires one corner post and one corner post cap. L-shaped walls need one corner post; U-shaped walls need two; more complex layouts need one per internal or external corner.
No. The 45° angle post has a different compound section profile to the 90° corner post. Contact our team for 45° angle post cap availability.
Water accumulates in the compound post cavity after every rain event. Internal corrosion progresses from the cut top face downward. In coastal or high-rainfall areas this can become visible within 12–18 months. The corner post is the most load-critical post in the wall: structural compromise here affects both wall runs simultaneously.
90° corner post caps ship Australia-wide via standard freight. Lightweight and easy to include with your post, sleeper, and drainage order for a single combined delivery. Trade account pricing available for builders, landscapers, and civil contractors: contact our team for volume pricing on your next project.
