The 100UC15 is one of the most commonly specified steel sections for low retaining walls across Melbourne and Victoria. Lightweight yet strong, this universal column profile is the go-to choice for garden walls, fence post applications and small landscaping retaining structures. At RW Steel Victoria, the 100UC15 (also called 100UC14.8) is one of our best-selling retaining wall posts.
100UC15 Dimensions and Properties
The designation “100UC15” refers to a Universal Column with a nominal depth of 100 mm and a mass of approximately 14.8 kg per metre (often rounded to 15 kg/m). Key dimensions:
Depth: 97 mm | Flange width: 99 mm | Flange thickness: 7.0 mm | Web thickness: 5.0 mm | Mass: 14.8 kg/m
The near-square profile (97 × 99 mm) makes the 100UC a true H-section, which is ideal for retaining walls because sleepers can slide down between the flanges on both sides of the web. This creates a neat, self-aligning wall face with no additional brackets or fixings required.
When to Use 100UC15 Posts
The 100UC15 is suitable for:
Garden retaining walls up to about 600 mm high using timber or concrete sleepers. At this height, the lateral soil pressure is modest and the 100UC section provides ample moment capacity when embedded in a proper concrete footing.
Decorative garden edging and raised beds where one or two sleepers are stacked. The compact profile keeps the posts unobtrusive while still providing structural support.
Fence posts in exposed locations where timber posts would rot or blow over. The 100UC15 in galvanised finish is a permanent, low-maintenance alternative.
For walls higher than 600 mm, you’ll generally need to step up to a 150UC or 200UC section. Check our guide to retaining wall steel sizes or request a quote for engineering-specific requirements.
Galvanised vs Bare Steel 100UC15
We supply 100UC15 posts in both bare (mill finish) and hot-dip galvanised options. For retaining walls, we almost always recommend galvanised. The buried portion of the post is in constant contact with damp soil, and without zinc protection the steel will begin to corrode within a few years. Hot-dip galvanising adds a tough zinc coating (typically 55–85 µm) that dramatically extends the service life of the post—often 30 years or more in typical Melbourne soil conditions.
If you’re building in highly acidic or saline soils (such as coastal areas or some parts of Gippsland), consider requesting an extra-heavy galvanised coating or adding a bituminous wrap to the buried section for additional protection.
Installation Tips for 100UC15 Posts
Proper installation ensures your retaining wall performs as designed:
Footing depth: Embed a minimum of 600 mm below finished ground level for walls up to 600 mm. Use N20 concrete in a 300 mm diameter hole.
Spacing: Post centres of 1.8 m to 2.1 m suit standard 1.8 m or 2.4 m sleepers. Ensure sleeper ends overlap the post flanges for a secure fit.
Alignment: Use a string line along the top of the posts to keep the wall straight. Brace each post temporarily until the concrete has cured for at least 24 hours.
Drainage: Install agricultural pipe behind the wall to prevent hydrostatic pressure build-up—the most common cause of retaining wall failure.
Order 100UC15 Posts from RW Steel Victoria
RW Steel stocks 100UC15 posts in standard lengths and can cut to your specific requirements. We deliver across Melbourne, Geelong, Ballarat, Bendigo, Gippsland and throughout Victoria. Browse our project gallery to see 100UC posts in action, or get in touch to discuss your project.