THE SMALL FASTENER THAT PLAYS A CRITICAL ROLE IN METAL ROOFING SYSTEMS

When discussing metal roofing systems, attention is often focused on the primary roofing screws that secure the roof sheet to the steel purlin.

However, experienced roofing contractors know that another fastener is equally important for ensuring the strength, weather resistance, and appearance of a roofing system:

The Stitch Screw.

Although much smaller than standard self drilling screws, stitch screws play a vital role in connecting overlapping metal sheets and finishing accessories. Selecting the correct stitch screw can significantly improve the durability and performance of an entire roofing installation.

WHAT IS A STITCH SCREW?

DESIGNED TO FASTEN SHEET TO SHEET

A Stitch Screw, also known as a Lap Screw or Side Lap Screw, is a self-drilling or self-tapping fastener specifically designed to connect two thin metal sheets together, rather than fastening steel sheets to structural members.

Unlike conventional roofing screws, stitch screws are not intended to drill into thick steel purlins. Their primary purpose is to secure overlapping metal panels and roofing accessories, ensuring a tight and stable connection.

Think of it as the fastener that “stitches” two sheets together—hence the name Stitch Screw.

WHY ARE STITCH SCREWS IMPORTANT?

MORE THAN JUST HOLDING TWO SHEETS TOGETHER

Metal roofing systems naturally expand and contract due to temperature changes.

If side laps are not securely fastened, several issues may occur:

• Panel vibration during strong winds
• Water penetration at overlapping joints
• Roof noise caused by sheet movement
• Loose flashing or ridge capping
• Reduced structural stability

A properly installed stitch screw keeps adjacent panels tightly connected, improving both appearance and long-term performance.

COMMON APPLICATIONS

Stitch screws are widely used throughout modern roofing and cladding systems.

METAL ROOF SIDE LAPS

The most common application is fastening overlapping roof sheets to minimise movement and prevent wind uplift.

WALL CLADDING PANELS

Used to secure vertical and horizontal panel overlaps while maintaining a clean exterior appearance.

RIDGE CAPS

Fastening ridge caps to roof sheets without penetrating structural steel.

FLASHINGS

Ideal for:

• Valley Flashings
• Apron Flashings
• Barge Flashings
• Corner Flashings

where only sheet-to-sheet fastening is required.

GUTTER ACCESSORIES

Used to assemble lightweight sheet metal components in drainage systems.

TYPICAL HEAD TYPES

Several head designs are available depending on the installation requirements.

HEX WASHER HEAD

The most common choice for roofing applications.

Advantages:

✔ High driving torque

✔ Easy installation

✔ Compatible with power tools

PAN HEAD

Suitable where a lower-profile appearance is preferred.

Commonly used for cladding and interior sheet metal applications.

WAFER HEAD

Provides a larger bearing surface for thin metal sheets, helping distribute clamping force more evenly.

COMMON DRIVE TYPES

Depending on market preference, stitch screws are available with:

• Phillips Drive
• Square Drive
• Torx Drive
• Hex Drive

Torx and Hex drives are increasingly popular due to their superior torque transfer and reduced driver slippage.

STANDARD SIZES

The most common stitch screw diameters include:

• ST4.2 (#8)
• ST4.8 (#10)

Typical lengths include:

• 13 mm (1/2″)
• 16 mm (5/8″)
• 19 mm (3/4″)
• 20 mm
• 25 mm

Since stitch screws are designed for thin sheet materials, they are generally shorter than standard roofing screws.

DRILL POINT OPTIONS

The drill point should match the total thickness of the metal sheets being joined.

SELF-DRILLING POINT

Suitable for thin steel sheet connections.

Ideal for:

• Metal roofing
• Steel cladding
• Flashings

SHARP POINT

Used where pre-punched holes or light-gauge materials are involved.

SHOULD STITCH SCREWS INCLUDE A WASHER?

IT DEPENDS ON THE APPLICATION

WITH EPDM BONDED WASHER

Recommended for:

• Roof side laps
• External cladding
• Weather-exposed installations

Benefits include:

✔ Improved waterproofing

✔ UV resistance

✔ Long-term sealing performance

WITHOUT WASHER

Suitable for:

• Interior installations
• Decorative panels
• Sheet metal assemblies where waterproofing is not required

SURFACE FINISH OPTIONS

To match different environments, stitch screws are commonly available in:

ZINC PLATED

Suitable for indoor applications.

YELLOW ZINC PLATED

Provides moderate corrosion resistance while maintaining an attractive appearance.

RUSPERT® CERAMIC COATING

Recommended for:

• Roofing systems
• Outdoor structures
• Industrial buildings

Offers outstanding corrosion resistance for long-term outdoor performance.

STAINLESS STEEL 304

Ideal for:

• Coastal environments
• Marine projects
• High-humidity regions

Provides excellent corrosion resistance throughout the service life of the building.

RECOMMENDED INSTALLATION SPACING

The required spacing depends on:

• Roof profile
• Wind load
• Panel design
• Local building regulations

As a general guideline:

• Install stitch screws at every overlap rib or as specified by the roofing system manufacturer.
• Do not overtighten, as excessive compression may deform the sheet or damage the EPDM washer.

Always follow the roofing manufacturer’s installation recommendations and local building codes.

COMMON INSTALLATION MISTAKES

USING ROOFING SCREWS INSTEAD OF STITCH SCREWS

Standard roofing screws are designed to penetrate structural steel and are often unnecessarily long for sheet-to-sheet connections.

USING STITCH SCREWS TO FASTEN INTO PURLINS

Stitch screws are not intended for structural fixing.

Roof sheets should always be secured to the purlins using appropriately sized roofing self-drilling screws.

INCORRECT TORQUE

Overtightening may:

• Damage the coating
• Distort the sheet
• Reduce waterproof performance

Proper torque ensures a secure connection without compromising the roof system.

DD FASTENERS STITCH SCREW SOLUTIONS

DD Fasteners offers a comprehensive range of Stitch Screws designed for professional roofing and cladding applications.

Our range includes:

• Hex Washer Head Stitch Screws
• Pan Head Stitch Screws
• Wafer Head Stitch Screws
• EPDM Bonded Washer Options
• Zinc Plated
• Ruspert® Ceramic Coating
• Stainless Steel 304
• Colour-Matched Painted Heads
• OEM & Private Label Packaging

Every product is manufactured to ensure consistent quality, reliable installation, and long-term performance in demanding construction environments.

FINAL THOUGHT

While Stitch Screws may be among the smallest fasteners in a roofing system, their contribution is anything but small.

They secure overlapping panels, improve wind resistance, reduce vibration, and help maintain a watertight building envelope.

A high-quality roofing system depends not only on the primary fasteners—but also on the details that hold everything together.

In roofing, every connection matters, and the right Stitch Screw makes all the difference.

CONTACT DD FASTENERS

For more information about:

• Stitch Screws
• Lap Screws
• Roofing Self Drilling Screws
• Cladding Fasteners
• OEM Fastening Solutions

Website: www.ddfasteners.com

E-mail: dd@ddfasteners.com

DD Fasteners
Professional Self Drilling Screw Manufacturer & Global Fastener Supplier