Key takeaways
- IBR is a five-rib profile with a 686 mm cover width and a 36–38 mm rib height, formed from 0.40–0.80 mm coated steel.
- Cover width (686 mm) is what you count for take-off; total sheet width (742 mm) and coil width (925 mm) are different numbers and using the wrong one mis-costs the job by 8–26%.
- Our 762 mm cover width set uses fewer sheets and fixings but has a shallower rib, so it needs more purlins. Note that 762 mm is a wide-span / corrugated cover width — it is not part of the IBR profile standard.
- IBR is ordered and checked by geometry — cover width, rib height, rib count and thickness — not by the profile name alone.
The short answer
IBR stands for Inverted Box Rib. It is a five-rib trapezoidal roofing profile with a **686 mm cover width** and a **36–38 mm rib height**, made from galvanised or colour-coated steel between 0.40 mm and 0.80 mm thick. Buyers in South Africa, the rest of Africa, the UK, Ireland, Australia and India order it by that name.
The reason a dimension question matters more for IBR than for most profiles is that the name alone does not describe the sheet. Two suppliers quoting "IBR" can deliver sheets that lap differently. The numbers below are the ones buyers actually check on delivery.
The dimensions that decide the order
Our IBR tooling is built to the 686 mm cover width standard. These are the tooling figures, measured on the formed sheet:
| Dimension | Value | Why it matters |
|---|---|---|
| Cover width | 686 mm (standard) | What you actually get per sheet after lapping — use this for quantity take-off, never the total width |
| Total sheet width | 742 mm (at 686 mm cover) | The physical width of the sheet as it leaves the machine |
| Coil width | 925 mm (for 686 mm cover) | What you must order from the coil supplier |
| Rib pitch | 171.5 mm | Five ribs across the 686 mm cover |
| Rib height | 36–38 mm | Sets the purlin spacer height and the screw length |
| Material thickness | 0.40–0.80 mm BMT | Base metal thickness before coating |
| Minimum roof pitch | 7.5° (standard IBR guidance) | Below this, end laps and side laps need sealing — check what your market expects |
Cover width, total width and coil width are three different numbers
Almost every IBR dispute comes from mixing these three up. The **total width** is the flat sheet the machine produces — 742 mm at the standard profile. The **cover width** is what that sheet covers once it is lapped onto its neighbour — 686 mm. The difference, 56 mm, is the side lap that makes the roof watertight.
The **coil width** is what you buy from the steel supplier — 925 mm — and it is wider than the finished sheet because the edges are trimmed to give a clean lap.
So when you calculate how many sheets a roof needs, divide the roof width by **686 mm**, not 742 mm and not 925 mm. Using the total width under-counts the sheets by roughly 8%, and using the coil width under-counts them by roughly 26%.
Our second tooling set (762 mm cover width), and when it is the better choice
A second tooling set on the same base machine produces a **762 mm cover width** profile with a shallower rib. Wider cover means fewer sheets and fewer fixings per square metre, which lowers both material handling and labour on large roofs.
The trade-off is stiffness. The wider profile has a shallower rib, so it spans less between purlins, which means closer purlin spacing and more steel in the structure. On a large industrial roof the two effects are usually compared directly: fewer sheets and fixings against more purlins.
Both widths run on the same machine — the forming rolls are changed on a cassette. If you sell into more than one market, this is the practical argument for a cassette machine rather than a fixed single-profile line.
One note on widths, because it causes real confusion when comparing suppliers. **686 mm is the standard IBR cover width**; **890 mm is a genuine IBR variant** used in some markets, and it needs its own tooling set. **762 mm, by contrast, is not part of the IBR profile standard** — that cover width belongs to the wide-span (Widespan / Widedek 760) and corrugated families. Our IBR tooling is built to 686 mm as standard, with a **762 mm cover width** available as a second cassette, so tell us which profile family and cover width you actually sell and we will confirm the tooling — a width number on its own does not identify the profile.
What to check when the sheets arrive
IBR is specified by geometry, so it is checked by geometry. The four checks buyers run on delivery are the cover width, the rib height, the number of ribs, and the material thickness. A sheet that is dimensionally close but has a different rib geometry will not lap with the sheets already on site, which is why "generic trapezoidal" is not an acceptable substitute.
Cover width and rib height are the two that decide whether the sheet is accepted. Measure them on a formed sheet with a tape and a calliper rather than relying on the drawing.
IBR compared with the other roofing profiles
IBR is one of four roofing profile families we build lines for. They are not interchangeable names for the same sheet:
| Profile family | Main markets | Cover width | Rib height |
|---|---|---|---|
| IBR 686 | South Africa, Africa, UK, Ireland, Australia, India | 686 mm | 36–38 mm |
| Corrugated | UK, Ireland, Australia, Africa, SE Asia | 762 mm typical | 17–19 mm |
| Trapezoidal TR4/TR5 | Europe, Russia, Middle East, Asia | 750–1000 mm | 18–35 mm |
| Standing seam | Global high-spec | 300–500 mm | 25–65 mm |