How to Specify a Box Profile Roofing Sheet (Complete Guide)

How to Specify a Box Profile Roofing Sheet (Complete Guide)

Complete Engineering & Procurement Guide

A box profile is generally:

• A trapezoidal roofing sheet

• With angular ribs

• Used in commercial & industrial roofing

• Often 1000 mm effective cover width

Common in:

• UK

• Europe

• Africa

• Middle East

• Asia

However, there are dozens of variants.

Specification must define geometry precisely.

1️⃣ What Defines a Box Profile?

A box profile is defined by:

✔ Rib height
✔ Rib pitch
✔ Rib top width
✔ Rib angle
✔ Number of ribs
✔ Effective cover width

Common naming format in Europe:

32/1000
35/1000
40/1000

First number = rib height (mm)
Second number = effective cover width (mm)

Example:
32/1000 = 32 mm rib height, 1000 mm cover width

2️⃣ Common Box Profile Variants

32/1000

• Rib height: 32 mm

• Cover width: 1000 mm

• Most common UK industrial profile

35/1000

• Rib height: 35 mm

• Slightly stronger

40/1000

• Rib height: 40 mm

• Higher structural performance

45/1000 and above

• Used in heavier industrial applications

Always confirm full cross-section drawing.

3️⃣ Finished Dimensions to Specify

Before tooling approval, confirm:

✔ Effective cover width
✔ Overall formed width
✔ Rib height
✔ Rib pitch
✔ Rib top width
✔ Rib side angle
✔ Minor rib detail (if present)
✔ Side lap configuration

Small changes significantly affect developed width.

4️⃣ Typical Coil Width

For 1000 mm cover box profile:

Typical coil width:

~1200–1250 mm

Depends on:

• Rib height

• Side lap geometry

• Thickness

• Bend allowance

Higher rib height increases developed width.

Never assume 1250 mm coil without calculation.

5️⃣ Thickness Range

Common thickness ranges:

Light commercial:
0.40–0.50 mm

Industrial:
0.50–0.70 mm

Heavy industrial:
0.70–1.0 mm

Structural deck versions:
1.0–1.2 mm

Machine must be designed for:

Maximum thickness + maximum yield strength.

6️⃣ Material Grade

Common grades:

G250
G350
G550 (very common in some regions)

In the UK and Africa:

G550 is frequently used.

Higher grade increases:

Forming force
Springback
Motor requirement
Shaft load

Machine frame rigidity must match grade.

7️⃣ Coating Specification

Common coatings:

Z275 galvanized
AZ150 (Aluzinc)
Prepainted (SMP / PVDF)

Industrial environments may require:

Higher corrosion protection.

Coating type affects roll surface finish requirement.

8️⃣ Rib Height & Structural Performance

Higher rib height provides:

✔ Greater stiffness
✔ Longer purlin spacing
✔ Better wind resistance

32 mm suitable for moderate spans.

40 mm and above for heavier loading.

Changing rib height requires structural recalculation.

9️⃣ Side Lap Detail

Box profiles typically:

Overlap one rib.

Specify:

✔ Side lap type
✔ Anti-capillary groove
✔ Fastener position

Incorrect side lap detail causes leakage.

🔟 Wind & Snow Load Considerations

Box profiles are widely used in:

High wind zones
Snow load regions

Specify:

✔ Minimum thickness
✔ Steel grade
✔ Rib height

Higher rib height improves load resistance.

Profile must match tested load tables.

1️⃣1️⃣ Machine Engineering Requirements

Typical 32/1000 box profile line:

• 16–22 forming stands

• 75–90 mm shafts

• 18.5–30 kW motor

• Hydraulic stop cut

• Optional flying shear

For 1.0 mm + thickness:

Larger shafts and higher motor power required.

G550 increases forming load significantly.

1️⃣2️⃣ Production Speed

Typical speeds:

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

Thicker material reduces maximum speed.

Cutting system influences cycle time.

1️⃣3️⃣ Tolerance Requirements

Typical tolerances:

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

Industrial markets require tighter tolerance than residential.

Machine rigidity and shaft size influence dimensional stability.

1️⃣4️⃣ Developed Width Reminder

Developed width includes:

✔ Bend angles
✔ Thickness compensation
✔ Springback correction

Box profile trapezoidal geometry significantly increases developed width beyond cover width.

Incorrect coil width is a frequent ordering mistake.

1️⃣5️⃣ Export Market Considerations

UK standard:
32/1000 very common.

Africa:
Often similar to UK but may use different rib angle.

Middle East:
May prefer deeper ribs.

Asia:
Multiple custom versions.

Always confirm market standard drawing.

1️⃣6️⃣ Common Specification Mistakes

❌ Saying “1000 mm box profile” without rib height
❌ Not specifying grade
❌ Ignoring coil width calculation
❌ Not confirming side lap detail
❌ Underestimating thickness range
❌ Not verifying structural requirement

These mistakes lead to costly tooling changes.

1️⃣7️⃣ Box Profile vs Corrugated Comparison

Box profile is more structural.

1️⃣8️⃣ Final Box Profile Specification Checklist

Before tooling or machine approval:

✔ Confirm rib height (e.g., 32 mm)
✔ Confirm cover width (e.g., 1000 mm)
✔ Confirm rib pitch
✔ Confirm side lap detail
✔ Confirm thickness range
✔ Confirm steel grade
✔ Confirm coating
✔ Calculate developed width
✔ Confirm coil availability
✔ Confirm wind/snow requirement
✔ Confirm production speed target

Only then proceed.

FAQ Section

Is 32/1000 the same everywhere?

No — geometry can vary slightly by region.

What is typical coil width for 32/1000?

Usually 1200–1250 mm, but must be calculated.

Is G550 common?

Yes, especially in Africa and some export markets.

Can I run 1.0 mm on a light machine?

Only if machine shaft and motor are designed for it.

Is box profile suitable for snow regions?

Yes — deeper ribs perform better.

Can rib height be modified?

Only with structural recalculation and tooling redesign.