Rebar Sizes in Kenya: Y8 to Y25, and What Each One Is For

Walk into any yard in Nairobi and you will hear the same bar called three different things. Your engineer wrote T16 on the drawing, the fundi asks for D16, and the price list says Y16. They are all the same bar. Y, D and T are just different conventions for high-yield deformed reinforcement bar, and the number after the letter is the bar diameter in millimetres. Work from the number and you will not go wrong.

What the sizes are normally used for

The structural drawing decides this, not habit — but it helps to know roughly where each size tends to land, so you can sanity-check an order before it arrives.

• Y8 — links and stirrups, the small bars tied around the main steel in a beam or column, plus light slab work.
• Y10 — slab reinforcement and lighter structural members.
• Y12 — the workhorse. Slabs, beams and strip foundations on most residential jobs.
• Y16 — columns, main beam steel and foundations.
• Y20 and Y25 — heavier columns, transfer beams and pile caps on larger structures.

Y bar and R bar are not the same

Y bar is deformed: it has ribs rolled into the surface so the concrete grips it, and it is what carries tension in a structural member. R bar is plain round mild steel with a smooth surface, used for links, hoops and general fabrication. If a drawing specifies one, the other is not a substitute.

Weight, and why it matters to the price

Steel is a weight business even when you buy it by the piece. The standard figures run roughly 0.395 kg per metre for Y8, 0.617 for Y10, 0.888 for Y12, 1.579 for Y16, 2.466 for Y20 and 3.854 for Y25. On a 12 m length, that is about 4.7 kg for a Y8 and about 46 kg for a Y25.

Two things follow from that. First, price per bar scales with the square of the diameter, not with the diameter — which is why a Y16 costs far more than twice a Y8. Second, a delivery of Y20 and Y25 gets heavy quickly, so transport and offloading need thinking about before the lorry arrives.

Comparing prices properly

Bar is stocked in 12 m lengths and we quote it per length. Other suppliers quote per metre or per tonne, which makes a straight comparison misleading — a per-metre figure looks dramatically cheaper than the same bar priced per 12 m length. Before you compare two quotes, check they are in the same unit.

Ask for the mill certificate

Reinforcement bar should be supplied to BS 4449:500B and the mill certificate should be available on request. Ask at the point of ordering rather than after delivery, so the certificate you get matches the batch that actually turns up on your site.

Working out how much you need

That comes off the bar schedule, which comes off the structural drawing. The spacing and size were chosen by your engineer for that specific element, and no rule of thumb replaces it. Send us the schedule or a clear photo of the drawing and we will work the quantities and price it.