How to Specify an IBR Roofing Profile (686 & 890 Variants)

Learn about how to specify an ibr roofing profile (686 & 890 variants) in roll forming machines. Profile Guide guide covering technical details

Complete Engineering & Procurement Guide

IBR stands for:

Inverted Box Rib

It is a trapezoidal roofing profile widely used in:

South Africa
Namibia
Botswana
Zambia
Zimbabwe
Parts of Europe

It is stronger than corrugated and commonly used for:

Industrial buildings
Warehouses
Commercial structures

But there are multiple IBR versions.

Correct specification is critical before tooling.

1️⃣ What Defines an IBR Profile?

IBR is defined by:

Trapezoidal rib geometry
Inverted box shape
Defined cover width
Specific rib height

The two most common versions:

IBR 686

Effective cover width: 686 mm
Rib height: approx. 38 mm

IBR 890

Effective cover width: 890 mm
Rib height: approx. 41 mm

Always confirm which version is required.

2️⃣ Standard Finished Dimensions

IBR 686 (Common Southern Africa)

Effective cover width: 686 mm
Rib height: ~38 mm
Rib pitch: ~171.5 mm centers
4 major ribs

IBR 890

Effective cover width: 890 mm
Rib height: ~41 mm
5 major ribs

Exact dimensions vary slightly by manufacturer.

Always confirm full cross-sectional drawing.

3️⃣ Typical Coil Width

Developed width depends on:

Rib height
Side lap detail
Bend angles
Thickness

Typical coil width:

IBR 686:
~910–940 mm coil

IBR 890:
~1200–1250 mm coil

Never assume coil width based on cover width alone.

Developed width must be calculated.

4️⃣ Thickness Range

IBR is stronger than corrugated.

Common thickness ranges:

Residential / Light Commercial:
0.40–0.50 mm

Commercial / Industrial:
0.50–0.60 mm

Heavy Industrial:
0.60–0.80 mm

Some structural applications may use:
1.0 mm

Machine must be engineered for:

Maximum thickness + maximum yield strength.

5️⃣ Material Grade

Common grades in Southern Africa:

G550 is very common.
G350 also used.

Higher strength steel is often preferred due to:

Wind exposure
Large roof spans

G550 significantly increases:

Forming load
Springback
Motor requirement
Shaft stress

Machine must be designed accordingly.

6️⃣ Coating Type

Common IBR coatings:

Z275 galvanized
AZ150 (Aluzinc)
Prepainted

In coastal areas:

AZ coating is preferred.

Coating influences:

Roll surface finish requirement
Corrosion performance

7️⃣ Rib Height & Structural Capacity

IBR rib height (38–41 mm) provides:

Higher structural stiffness than corrugated.

This allows:

Longer purlin spacing
Better wind uplift performance

Changing rib height alters structural performance.

Do not modify without structural recalculation.

8️⃣ Side Lap & Overlap Detail

IBR typically overlaps:

One rib.

Specify:

✔ Side lap configuration
✔ Fastener position
✔ Sealant requirement
✔ Anti-capillary groove presence

Overlap geometry impacts water tightness.

🔟 Developed Width Reminder

Developed width must include:

Bend allowance
Thickness compensation
Springback correction

IBR trapezoidal geometry increases developed width compared to shallow profiles.

Incorrect coil width is one of the most common IBR specification errors.

1️⃣1️⃣ Machine Engineering Requirements

Typical IBR machine:

16–22 forming stands
75–90 mm shafts (depending on thickness & grade)
18.5–30 kW motor
Hydraulic stop cut (standard)
Flying shear (high-speed lines)

Because G550 is common, machines must be structurally strong.

1️⃣2️⃣ Production Speed

Typical speeds:

15–25 m/min (standard)
30–40 m/min (high-speed lines)

Higher thickness reduces speed potential.

Cutting system influences maximum rate.

1️⃣3️⃣ Tolerance Requirements

IBR typically requires:

Width ±2 mm
Rib height ±1 mm
Length ±2–3 mm

Structural applications require tighter tolerance than agricultural roofing.

Machine rigidity directly impacts dimensional stability.

1️⃣4️⃣ Wind & Structural Compliance

IBR commonly used in:

High wind regions.

Compliance may require:

Wind uplift testing
Local building code approval

Profile must match tested geometry exactly.

Altering:

Thickness
Rib height
Grade

Invalidates structural data.

1️⃣5️⃣ Export Considerations

IBR 686 is strongly associated with:

Southern African markets.

Exporting to those markets requires:

Matching local geometry precisely.

Minor geometry deviations cause installation incompatibility.

Always confirm local standard drawing.

1️⃣6️⃣ Common Specification Mistakes

❌ Saying “IBR” without specifying 686 or 890
❌ Not confirming rib height
❌ Ignoring G550 requirement
❌ Guessing coil width
❌ Not defining overlap detail
❌ Not verifying wind load requirement

Most tooling errors originate from incomplete IBR specification.

1️⃣7️⃣ IBR 686 vs 890 Summary

Feature	IBR 686	IBR 890
Cover Width	686 mm	890 mm
Rib Height	~38 mm	~41 mm
Coil Width	~910–940 mm	~1200–1250 mm
Common Market	Southern Africa	Broader industrial

Confirm which variant before tooling design.

1️⃣8️⃣ Final IBR Specification Checklist

Before approving tooling or machine:

✔ Confirm 686 or 890
✔ Confirm rib height
✔ Confirm rib pitch
✔ Confirm thickness range
✔ Confirm steel grade
✔ Confirm coating
✔ Calculate developed width
✔ Confirm coil supply availability
✔ Confirm production speed target
✔ Confirm wind/load requirements
✔ Confirm export standard alignment

Only then proceed to production.

FAQ Section

Is IBR always 686 mm?

No — 890 variant is also common.

Is G550 required for IBR?

Often in Southern Africa, yes.

What is typical coil width?

686 → approx. 910–940 mm
890 → approx. 1200–1250 mm
Exact width must be calculated.

Is IBR stronger than corrugated?

Yes — deeper rib provides greater stiffness.

Can I change rib height slightly?

Not without affecting structural performance.

Is IBR suitable for high wind zones?

Yes — if thickness and grade are correct.