250UB25 is the deep, economical option for taller sleeper retaining walls. At 248 mm deep it delivers a large section modulus about its major axis while weighing barely 26 kilograms per metre. On a long wall that difference shows up in both the steel invoice and the handling plant you need on site. The catch is a relatively narrow flange, so it is not a drop-in substitute for a universal column in every situation.
250UB25 dimensions and grade
- Nominal depth: 248 mm
- Flange width: 124 mm
- Flange thickness: 8.0 mm
- Web thickness: 5.0 mm
- Mass: 25.7 kg per metre
- Grade: typically 300PLUS to AS/NZS 3679.1
The extra 50 mm of depth over a 200UB18 is what buys the capacity: bending strength grows quickly with depth, so a modest increase in weight gives a substantial jump in what the post can hold back.
Retained heights and post spacing
Subject always to engineering, 250UB25 at 1.5 m centres in reasonable soil with level backfill and no surcharge is commonly used for retained heights around 1.2–1.6 m. Two levers change that:
- Spacing. Dropping from 1.5 m to 1.2 m centres reduces the load on each post by about 20 percent and often costs less than upsizing the section, because footings stay smaller.
- Surcharge. A driveway, carport or slab behind the wall can add the equivalent of several hundred millimetres of extra soil height and will pull the usable height back sharply.
Where surcharge or heights above roughly 1.6 m are involved, engineers generally specify a universal column instead — see our notes on 200UC posts and 250UC for maximum strength.
250UB25 versus 200UC46.2
This is the real decision for mid-to-tall walls. The UB is deeper and much lighter, so material cost per metre of wall is lower and posts are easier to place. The UC has wide, thick flanges: better lateral stiffness, more sleeper bearing, more tolerance for thick premium sleepers, and more reserve if the footing is less than ideal. Choose the 250UB25 for straight, well-drained runs with standard sleepers where budget matters. Choose the UC for exposed walls, heavy sleepers, corners, or anywhere the design is close to its limit. Our UC versus UB comparison goes deeper on the trade-off.
Footings and embedment
Typical practice for a 250UB25 is a concrete footing 450–600 mm in diameter with embedment of one third to one half of the total post length, sized by the engineer for the soil classification. Because a UB is much stiffer in one direction than the other, orientation and plumbness matter: set the web perpendicular to the wall face, brace each post in two planes, and let footings cure before backfilling. The retaining wall specifications guide covers how these numbers hang together.
Drainage is not optional at this height
At 1.2 m and above, water is the biggest single risk. Install an ag drain wrapped in geofabric at the base of the wall, backfill with free-draining aggregate for at least 300 mm behind the sleepers, and make sure the drain discharges somewhere real. A blocked drain can double the pressure on a wall — no post size compensates for that.
Galvanising and supply
Specify hot-dip galvanising to AS/NZS 4680 for anything in soil, and order posts cut to length and drilled before galvanising so no bare steel goes underground. We supply 250UB25 across Melbourne, Geelong and Gippsland, including Traralgon and the Latrobe Valley, alongside the rest of our retaining wall steel range and matching concrete sleepers.
Get a price on 250UB25 posts
Send your engineer’s schedule, or just the wall heights and total length, through the quote and order form and we will come back with cut-to-length galvanised pricing. You can also contact the team directly, or see comparable walls in the project gallery.