200UB18 is one of the most cost-effective retaining wall posts on the market. At just over 18 kilograms per metre it is light enough for two people to place by hand, but 200 mm deep, which gives it real bending strength for low and mid-height sleeper walls. The trade-off is a narrower flange than a universal column, and that is the detail worth understanding before you order.
200UB18 dimensions
- Nominal depth: 198 mm
- Flange width: 99 mm
- Flange thickness: 7.0 mm
- Web thickness: 4.5 mm
- Mass: 18.2 kg per metre
- Grade: typically 300PLUS / AS/NZS 3679.1
The 99 mm flange is the key number. It sets how much sleeper bearing you have on each side of the web, so 200UB18 suits standard-thickness concrete sleepers rather than the heaviest premium profiles. Check thickness against the sleeper range before finalising a size.
What heights does 200UB18 suit?
With posts at 1.5 m centres in reasonable soil and no surcharge, 200UB18 is commonly used for retained heights up to roughly 0.9–1.2 m. Tightening the spacing to 1.2 m centres buys extra capacity and is often cheaper than stepping up a section size, because you avoid larger footings. Above about 1.2 m, or wherever a driveway or structure sits behind the wall, engineers usually move to 200UC or 250UB25.
200UB18 versus 150UC23.4
These two compete for the same jobs. The 200UB18 is deeper, so it has slightly more bending capacity about its major axis while weighing about 22 percent less per metre. The 150UC23.4 has a much wider, thicker flange, so it is stiffer laterally, more tolerant of thick sleepers and more forgiving if a post is not perfectly plumb. Rule of thumb: choose 200UB18 for straight runs of standard sleepers where cost and handling matter; choose the UC where sleepers are heavy, the wall is exposed, or lateral stability is a concern.
Footings and installation
A 200UB18 post is typically set in a 400–450 mm diameter concrete footing with embedment of one third to one half of total post length, subject to engineering. Because the section is relatively light, it is easy to knock out of plumb during backfill — brace posts until the concrete has cured properly, and never run a compaction plate hard against a freshly built wall. Align the flange slots on a string line before the concrete sets; a 5 mm wander per post becomes very visible over a ten-post run.
Galvanising
Specify hot-dip galvanising to AS/NZS 4680. The thinner web and flange of a UB mean corrosion has less steel to eat through than on a heavy column, so coating quality matters more, not less. Order posts cut and drilled to length before galvanising so no bare steel is left in the ground. Everything in our retaining wall steel range can be supplied hot-dip galvanised.
Where 200UB18 works well
- Garden bed and terraced landscaping walls between 600 mm and 1.0 m
- Long boundary runs where handling weight and cost add up
- Levelling a gently sloping backyard for lawn or decking
- Second and third terraces above a heavier engineered base wall
Pricing and supply
We stock 200UB18 in standard lengths and cut to order for jobs across Melbourne and regional Victoria. Send your wall heights, total length and sleeper type through the quote and order form for a price, browse finished walls in the gallery, or contact us if you want to sanity-check a size before you commit.