How to Specify Drip Edge (Complete Roofing Trim Guide)

Learn about how to specify drip edge (complete roofing trim guide) in roll forming machines. Profile Guide guide covering technical details

Complete Engineering & Roofing Guide

Drip edge is installed at:

Eaves (bottom roof edge)
Rakes (gable edges)

It directs water away from:

✔ Fascia board
✔ Roof decking
✔ Building envelope

It also supports:

✔ Starter strip
✔ Underlayment termination
✔ Edge wind resistance

Drip edge is not one-size-fits-all.

1️⃣ What Defines a Drip Edge?

Drip edge is defined by:

✔ Profile type (L-style, T-style, D-style, F-style)
✔ Leg length (roof leg)
✔ Vertical face height (fascia leg)
✔ Hem detail
✔ Material thickness
✔ Material type
✔ Coating
✔ Installation location (eave or rake)

Each variable affects performance.

2️⃣ Profile Types

L-Style (Type C)

Simple 90° angle.

Used for:
Basic eaves and rakes.

T-Style (Type D)

Has small outward flange at bottom.

Improves:
Water drip separation.

F-Style (Gutter apron)

Longer top flange.

Used when:
Installed over existing shingles or for retrofit.

Always specify profile type.

3️⃣ Leg Length (Roof Flange)

Common roof flange lengths:

50 mm
75 mm
100 mm

Longer flange improves:

✔ Water protection
✔ Wind resistance

Short flange may be insufficient in heavy rain regions.

Must match underlayment detail.

4️⃣ Fascia Leg Height

Common fascia leg heights:

50 mm
75 mm
100 mm

Height must match:

Fascia board size
Roof overhang design

Too short → water backflow.
Too long → aesthetic mismatch.

5️⃣ Hem Detail

Bottom edge may include:

✔ Safety hem
✔ Double hem
✔ Drip kick

Hem improves:

✔ Stiffness
✔ Water drip separation
✔ Safety

Hem affects developed width and material cost.

Must be specified.

6️⃣ Thickness Range

Common thickness:

0.40 mm
0.45 mm
0.50 mm
0.60 mm

Residential drip edge often thinner.

High wind zones require thicker material.

Thickness affects:

Wind resistance
Stiffness
Oil canning risk

7️⃣ Material Type

Common materials:

Galvanized steel
Galvalume (AZ coated)
Prepainted steel
Aluminum

Coastal environments often prefer:

Aluminum or AZ coated steel.

Material must match roof system.

8️⃣ Coating & Finish

Drip edge should match roof panel finish.

Specify:

✔ Zinc coating mass (Z275, etc.)
✔ AZ coating weight
✔ Paint system (SMP, PVDF)
✔ Color

Finish impacts:

Corrosion resistance
Aesthetic integration
Warranty alignment

9️⃣ Wind Zone Considerations

Roof edges experience high uplift forces.

In high wind zones:

✔ Increase thickness
✔ Increase flange length
✔ Reduce fastener spacing
✔ Use hemmed profile

Drip edge must be mechanically secured properly.

🔟 Installation Position

Specify whether drip edge is for:

✔ Eave (installed under underlayment)
✔ Rake (installed over underlayment)

Eave and rake versions may differ slightly.

Installation sequence matters.

1️⃣1️⃣ Gutter Compatibility

If gutters are present:

Drip edge must:

✔ Direct water into gutter
✔ Align with gutter lip
✔ Avoid water overshoot

Profile selection must consider gutter system.

1️⃣2️⃣ Typical Coil Width

Coil width =

Roof flange + fascia leg + hem + bend allowance.

Example:

75 mm roof leg
75 mm fascia leg

150 mm + bend allowance → approx. 165–185 mm coil

Exact developed width must include:

Bend radius
Thickness compensation
Hem allowance
Springback correction

Never approximate coil width.

1️⃣3️⃣ Machine Engineering Requirements

Drip edge can be produced on:

✔ Trim roll forming machine
✔ Press brake
✔ Multi-profile trim line

Typical trim machine:

6–10 forming stands
40–60 mm shafts
3–7 kW motor
Hydraulic cut

Simple geometry allows flexible production.

1️⃣4️⃣ Production Speed

Typical speeds:

15–30 m/min

Higher speed possible due to simple geometry.

1️⃣5️⃣ Tolerance Requirements

Typical tolerances:

Angle ±1°
Leg length ±1–2 mm
Length ±2–3 mm

Angle accuracy critical for flush installation.

1️⃣6️⃣ Code Requirements

In many countries:

Drip edge is required by building code.

Code may define:

✔ Minimum flange size
✔ Fastener spacing
✔ Installation method

Always confirm local building regulations.

1️⃣7️⃣ Common Specification Mistakes

❌ Not specifying profile type
❌ Not matching fascia size
❌ Ignoring wind zone
❌ Using too thin material
❌ Not defining hem
❌ Guessing coil width

Drip edge mistakes often cause water damage issues.

1️⃣8️⃣ Developed Width Reminder

Developed width must include:

✔ Roof flange
✔ Fascia leg
✔ Hem allowance
✔ Bend allowance
✔ Thickness compensation
✔ Springback correction

Even simple trims require proper calculation.

1️⃣9️⃣ Final Drip Edge Specification Checklist

Before tooling or machine approval:

✔ Confirm profile type
✔ Confirm roof flange length
✔ Confirm fascia leg height
✔ Confirm hem detail
✔ Confirm thickness range
✔ Confirm material type
✔ Confirm coating
✔ Confirm wind zone requirement
✔ Confirm installation position (eave or rake)
✔ Calculate developed width
✔ Confirm coil availability
✔ Confirm production speed target

Only then proceed.

FAQ Section

Is drip edge mandatory?

In many regions, yes.

Should drip edge match roof thickness?

Usually similar or slightly thinner.

Is aluminum better for coastal?

Yes — corrosion resistance is superior.

Does hem matter?

Yes — improves stiffness and water drip.

Can drip edge be press-braked?

Yes for low volume.

Is coil width small?

Yes — typically narrow trim width.