The 150UC is one of the most versatile and commonly specified steel sections for retaining wall construction across Victoria. Sitting in the sweet spot between lighter H-channel posts and heavier 200UC or 250UC columns, the 150UC offers excellent structural performance for medium-height walls without the cost and handling weight of larger sections. Here’s everything you need to know about using 150UC posts in your next retaining wall project.
What Is a 150UC?
The 150UC (Universal Column) is a structural steel section with an H-shaped cross-section. The “150” refers to the nominal depth of the section in millimetres, while “UC” indicates it is a Universal Column — characterised by flanges that are approximately equal in width to the section depth, giving it a near-square profile.
The most common grade used in retaining wall applications is the 150UC23.4, which weighs 23.4 kg per metre. Key dimensions include:
150UC23.4 dimensions: 152mm depth × 152mm flange width × 6.8mm web thickness × 9.4mm flange thickness. The section modulus (Zx) is approximately 171 cm³, giving it significantly more bending capacity than standard H-channel posts.
When to Use 150UC for Retaining Walls
The 150UC is the ideal choice for retaining walls in the 800mm to 1,200mm retained height range. At these heights, lighter H-channel sections start to reach their structural limits, while jumping to a 200UC or 250UC may be unnecessary and more expensive.
Common applications for 150UC retaining wall posts include:
• Residential boundary walls up to 1.2m retained height
• Garden terracing on sloped blocks
• Driveway retaining where vehicle surcharge loads apply
• Pool surrounds where consistent height and clean lines are required
• Light commercial retaining in car parks and access roads
For walls over 1.2m in retained height, or where significant surcharge loads are present (such as driveways or structures near the wall top), a structural engineer may specify 250UC posts or additional bracing. Always check with your engineer before finalising the post size for walls over 1m.
150UC vs Other Steel Post Sizes
Understanding how the 150UC compares to other common sections helps you make the right choice:
100UC vs 150UC: The 100UC (100UC14.8) has roughly half the bending capacity of the 150UC. It’s suitable for low walls under 600mm but lacks the strength for medium-height applications. The 150UC is the safer, more capable choice for anything above that range.
150UC vs 200UC: The 200UC (200UC46.2) offers approximately twice the bending capacity of the 150UC but weighs almost double. For walls between 800mm and 1,200mm, the 150UC is usually sufficient and much easier to handle on site. The 200UC comes into play for walls approaching 1.5m or where heavy loads are expected.
150UC vs H-channel posts: Standard galvanised H-channel posts are lighter and cheaper but have significantly less structural capacity. They’re perfect for low garden walls but cannot match the 150UC for medium-height retaining applications. If your wall is over 800mm, stepping up to a 150UC is strongly recommended.
Galvanised 150UC Posts
For retaining wall use, galvanised 150UC posts are the preferred option. Hot-dip galvanising protects the steel from corrosion in the buried section where moisture and soil contact are constant. A standard galvanised coating provides 50+ years of protection in most Victorian soil types.
At RW Steel Victoria, we supply galvanised 150UC posts cut to your required lengths. Galvanising is applied after cutting, ensuring full protection on all surfaces including the cut ends — a critical detail that some suppliers miss.
Installation Tips for 150UC Posts
Installing 150UC posts follows the same general principles as any steel retaining wall post, with a few important considerations due to the heavier section:
Post hole size: Dig holes at least 450mm diameter to accommodate the 152mm-wide flange and leave room for concrete placement. A 500mm auger is ideal.
Buried depth: Bury at least one-third of the total post length. For a 1m retained height wall with a 2.1m total post length, the buried depth should be approximately 700mm plus a 100mm gravel drainage base.
Concrete specification: Use N20 (20 MPa) or N25 concrete around each post. For 150UC posts, allow approximately 0.08–0.10 m³ of concrete per hole, depending on hole diameter and depth.
Post spacing: Typical spacing for 150UC retaining wall posts is 1.5m to 2.0m centre-to-centre, depending on wall height and sleeper thickness. Closer spacing reduces bending moments and allows thinner sleepers.
Order 150UC Steel Posts From RW Steel Victoria
We keep 150UC sections in stock at our Victorian warehouse and can cut to any length you need. Available in raw steel or hot-dip galvanised finish, with delivery across Melbourne, Gippsland, and regional Victoria.
Check out our gallery for completed retaining wall projects using 150UC posts. For pricing and availability, request a quote online or get in touch with our team today.