What Coil Size Do I Need for Side Wall Flashing?

Side Wall Flashing Coil Size Guide (Before Forming)

Side wall flashing is installed where a roof meets a vertical wall, providing a watertight seal that prevents water from entering the building. It is commonly used in metal roofing systems, extensions, and industrial buildings.

The most important starting point in production is selecting the correct coil size before forming — especially the coil width, which defines how the flashing fits both the roof panel and the wall.

For side wall flashing, coil size directly affects:

• Coverage along the roof and wall junction
• Profile fit and sealing performance
• Overlap and fixing areas
• Hem and edge formation
• Production efficiency

This guide explains exactly what coil size you need before forming side wall flashing.

What Is Included in “Coil Size”?

Coil size includes:

• Coil width (most critical)
• Thickness (gauge)
• Coil weight
• Coil inside diameter (ID)
• Coil outside diameter (OD)
• Material type and coating

All must match both flashing design and forming equipment.

1. Coil Width (Primary Factor)

The most important factor is the coil width before forming, based on the developed strip width.

For side wall flashing, this includes:

• Roof flange (over or under roof panel)
• Vertical wall leg (upstand)
• Overlap sections
• Hemmed edges (if included)
• Bend allowances

Typical coil width ranges:

• 250 mm – 400 mm → small residential flashing
• 400 mm – 650 mm → standard applications
• 650 mm – 1000 mm+ → large or commercial systems

👉 Coil width must match roof coverage + wall height + hems

2. Thickness (Gauge)

Side wall flashing uses light to medium gauge materials.

Typical ranges:

• 0.3 mm – 0.5 mm → aluminum flashing
• 0.4 mm – 0.6 mm → standard steel flashing
• 0.6 mm – 1.0 mm+ → heavy-duty or industrial applications

Thickness affects:

• Formability
• Rigidity
• Durability
• Sealing performance

3. Coil Weight

Coil weight depends on production setup.

Typical coil weights:

• 0.5 – 2 tons → small/manual production
• 2 – 5 tons → standard roll forming
• 5 tons+ → high-volume systems

4. Coil Inside Diameter (ID)

The coil ID must match the uncoiler.

Common sizes:

• 300 mm – 400 mm → small coils
• 508 mm (20”) → standard
• 610 mm (24”) → larger systems

5. Coil Outside Diameter (OD)

OD depends on coil weight and thickness.

Typical OD:

• 800 mm – 1500 mm+

Must match:

• Uncoiler capacity
• Handling systems
• Production layout

6. Material Type and Coating

Material selection is critical for weather resistance and compatibility with building materials.

Common materials:

• Pre-painted galvanized steel
• Aluminum
• Coated steel

Material affects:

• Corrosion resistance
• Flexibility for forming
• Appearance

Why Coil Size Is Critical for Side Wall Flashing

Side wall flashing must create a tight seal between roof and wall.

If coil size is incorrect:

• Coverage may be insufficient
• Water may penetrate the joint
• Profile geometry may be inaccurate
• Hems may not form correctly
• Installation issues will occur

Accuracy is critical for weatherproofing and durability.

Sealing and Profile Geometry (Key Feature)

Side wall flashing includes:

• A horizontal section covering the roof panel
• A vertical section against the wall
• Overlaps for sealing
• Optional hems for strength

These require:

• Precise coil width
• Accurate bending
• Consistent forming

Incorrect coil size affects:

• Sealing performance
• Alignment with roof panels
• Installation quality

Common Coil Size Mistakes

Incorrect width

• Flashing does not cover both surfaces properly

Not allowing for overlaps and hems

• Poor sealing and weak edges

Wrong thickness

• Too flexible OR difficult to form

Incorrect material

• Reduced durability or corrosion resistance

Poor slitting quality

• Edge defects and finish issues

Machine Matching (Critical)

Before ordering coil, confirm your machine supports:

• Coil width range
• Thickness range
• Maximum coil weight
• Hemming capability
• Material compatibility

👉 Coil size must match machine + flashing design

What Buyers Must Confirm Before Ordering Coil

Always confirm:

• Side wall flashing design (dimensions and overlaps)
• Developed strip width
• Thickness
• Material type and finish
• Coil weight
• Coil ID / OD
• Machine limits

Never estimate — always ensure roof-to-wall compatibility.

Final Thoughts

For side wall flashing, the coil size before forming defines sealing performance, fit, and durability.

Getting the coil size right ensures:

• Proper coverage of roof and wall junction
• Accurate profile dimensions
• Clean hems and edges
• Reliable water protection
• Efficient production

Side wall flashing is critical for leak prevention — coil size accuracy is essential.

FAQ

What coil size do I need for side wall flashing?

You need the correct coil width, thickness, weight, ID/OD, and material type based on the flashing design.

What is the most important factor?

Coil width — it defines coverage and sealing.

Why is side wall flashing important?

It prevents water ingress where the roof meets a wall.

Does thickness affect performance?

Yes — it affects durability and rigidity.

Can coil size be adjusted during production?

No — it must be correct before forming.