How to Specify a Top Hat Section (Complete Engineering Guide)

It resembles an inverted hat shape.

Complete Structural & Manufacturing Guide

A Top Hat section is a:

Cold-formed profile with:

• ✔ Flat top flange
• ✔ Two vertical webs
• ✔ Two outward bottom flanges

It resembles an inverted hat shape.

It is typically used as:

• ✔ Secondary support member
• ✔ Batten for cladding
• ✔ Ceiling support rail
• ✔ Sub-framing element

Specification must define both geometry and structural requirement.

1️⃣ What Defines a Top Hat Section?

Top Hat is defined by:

• ✔ Top flange width
• ✔ Section height
• ✔ Bottom flange width
• ✔ Thickness
• ✔ Steel grade
• ✔ Span
• ✔ Load requirement
• ✔ Coating

Without load and span data, section size cannot be selected properly.

2️⃣ Typical Dimensions

Common top flange widths:

• 30 mm
• 40 mm
• 50 mm
• 75 mm
• 100 mm

Common heights:

• 20 mm
• 25 mm
• 40 mm
• 50 mm
• 75 mm

Common bottom flange width:

15–40 mm

Height is the main stiffness driver.

Increasing height increases bending resistance significantly.

3️⃣ Thickness Range

Common thickness:

• 0.45 mm
• 0.50 mm
• 0.60 mm
• 0.75 mm
• 1.0 mm
• 1.2 mm

Cladding battens often lighter gauge.

Structural secondary framing requires thicker material.

Machine must support maximum thickness.

4️⃣ Steel Grade

Common grades:

• G250
• G350
• G550

Higher grade:

✔ Increases load capacity
✔ Allows reduced thickness

But increases:

• Springback
• Forming force
• Roll wear

Grade must be defined before tooling design.

5️⃣ Span & Load Requirement (Critical)

Before selecting profile size:

• ✔ Define span between supports
• ✔ Define uniform load (cladding weight, wind pressure)
• ✔ Define point loads (solar brackets etc.)
• ✔ Define deflection limit

Common deflection criteria:

• L/180
• L/200
• L/250

Top Hat selection is governed more by deflection than strength.

6️⃣ Wind Load Consideration

In façade and cladding systems:

• ✔ Wind pressure can be high
• ✔ Uplift loads critical
• ✔ Fastener pull-out matters

Wind zone must be defined before section sizing.

Never choose profile only by appearance.

7️⃣ Cladding Compatibility

Top Hat must align with:

• ✔ Screw fixing pattern
• ✔ Panel rib spacing
• ✔ Insulation system
• ✔ Thermal break detail

Top flange width must suit:

Fastener placement.

Incorrect flange width causes fixing issues.

8️⃣ Coating & Corrosion Protection

Common finishes:

• Z275
• Z350
• Z450
• AZ coated
• Powder coated

Exterior façade systems may require higher corrosion resistance.

Coating impacts:

• Service life
• Warranty
• Forming wear

🔟 Typical Coil Width

Coil width =

Top flange + 2 webs + 2 bottom flanges + bend allowance.

Example simplified:

• 50 mm top
• 40 mm webs ×2
• 20 mm flanges ×2

50 + 80 + 40 = 170 mm
Add bend allowance → approx. 190–220 mm

Exact developed width must include:

• ✔ Bend radii
• ✔ Thickness compensation
• ✔ Springback correction

Never approximate developed width.

1️⃣1️⃣ Machine Engineering Requirements

Top Hat roll forming line:

• 10–18 forming stands

• 50–75 mm shafts

• 11–30 kW motor

• Hydraulic cut-off

Light gauge lines can run high speed.

Heavier structural top hats require stronger shafts and frame.

1️⃣2️⃣ Production Speed

Typical speeds:

20–50 m/min (light gauge)
Lower for thicker sections

Simple geometry allows high-speed production.

1️⃣3️⃣ Tolerance Requirements

Typical tolerances:

• Height ±1 mm
• Width ±1 mm
• Length ±2 mm
• Straightness critical

Twist must be controlled.

Twisted sections cause façade misalignment.

1️⃣4️⃣ Structural Optimization

Design rules:

• ✔ Increase height before increasing thickness (more efficient)
• ✔ Avoid very narrow webs (buckling risk)
• ✔ Ensure adequate bottom flange for stability
• ✔ Keep bend radii realistic

Small geometry changes greatly affect stiffness.

1️⃣5️⃣ Common Specification Mistakes

• ❌ Not defining span
• ❌ Ignoring wind load
• ❌ Using too thin material
• ❌ Not defining deflection limit
• ❌ Guessing coil width
• ❌ Overdesigning thickness instead of height

Most failures are deflection-related.

1️⃣6️⃣ Developed Width Reminder

Developed width must include:

• ✔ Top flange
• ✔ Webs
• ✔ Bottom flanges
• ✔ Bend allowance
• ✔ Thickness compensation
• ✔ Springback correction

Even simple sections require precise flat pattern.

1️⃣7️⃣ Final Top Hat Specification Checklist

Before tooling or machine approval:

• ✔ Confirm top flange width
• ✔ Confirm section height
• ✔ Confirm bottom flange width
• ✔ Confirm thickness range
• ✔ Confirm steel grade
• ✔ Confirm coating
• ✔ Confirm span
• ✔ Confirm load requirement
• ✔ Confirm deflection limit
• ✔ Calculate developed width
• ✔ Confirm coil availability
• ✔ Confirm production speed target

Only then proceed.

FAQ Section

Is height more important than thickness?

Yes — height increases bending stiffness much more efficiently.

Can Top Hat be used structurally?

Yes — for secondary structural support.

Is G550 common?

Yes in light gauge structural framing.

Can one machine run multiple sizes?

Yes with adjustable tooling.

Is coil width small?

Yes — typically under 250 mm.

Does wind zone matter?

Critical for façade and cladding systems.