Fixing and buying guide

What this product is and who needs it

Twin and combination flashings are essential components for installing VELUX roof windows on pitched roofs. Unlike single-function flashings, this product integrates both weatherproofing and structural support, managing water shedding whilst distributing the window load across the roof structure. It is designed for builders, roofers, and experienced DIY installers working on new roof window installations or replacements on pitched roof properties with tile or slate finishes.

Sizing and compatibility

This flashing measures 55x78cm and is sized for standard pitched roof applications. It is compatible with VELUX roof window ranges and suits both tile and slate roof finishes. Before purchasing, confirm that your VELUX window model is compatible with the EBW CK02 0021C flashing code, as different window sizes and roof types may require different flashing specifications. Check your window documentation or contact VELUX technical support if you are unsure of the correct size for your installation.

• Dimensions: 55cm wide by 78cm high
• Suitable for tile and slate pitched roofs
• Verify VELUX window compatibility before ordering
• One flashing per roof window installation

Pre-installation checks and preparation

Inspect the flashing on arrival for any damage to the metal or seals. Check that your roof structure is sound and that the roof opening is correctly sized and positioned for this flashing. Ensure you have the correct VELUX window model to hand and review the installation instructions supplied with both the window and flashing. Prepare the roof area by removing old flashing if replacing an existing window, and ensure the roof deck and surrounding tiles or slates are clean and in good condition.

• Inspect flashing for damage before installation
• Confirm roof opening dimensions match flashing size
• Have VELUX window installation instructions available
• Clean roof area and remove old flashing if applicable
• Check roof structure is sound and properly ventilated

Installation overview

The twin and combination design simplifies installation by combining weatherproofing and support functions. Position the flashing around the roof window opening, ensuring it sits correctly on the roof deck and integrates with the surrounding tile or slate courses. The integrated design reduces the number of separate components to install and seal, streamlining the process whilst maintaining weather resistance. Follow VELUX installation guidance closely, as correct positioning and sealing are essential for long-term roof integrity and water resistance. This is a specialist task; if you are not experienced in roof work, engage a qualified roofer or installer.