Fixing and buying guide

What this product is and who needs it

This is a roof flashing designed to seal the gap between your roof structure and a ventilation opening. You need it when installing VELUX roof vents or compatible ventilation systems on any roof type. The twin design makes it suitable for both new installations and replacements where you need a reliable, long-lasting weatherproof seal.

Compatibility and sizing

The flashing is sized at 78cm × 140cm and is compatible with timber grades F16 and F24, which covers standard structural timber used in UK construction. It works with VELUX roof vents and standard compatible ventilation systems. The generous dimensions provide ample working space during installation, reducing the risk of installation errors. Check your roof pitch type before ordering: this flashing suits flat roofs, pitched roofs, and roof pitch transitions.

• Size: 78cm × 140cm (47 inches × 55 inches)
• Material: PVC for durability and weather resistance
• Compatible timber grades: F16 and F24
• Suitable for: flat roofs, pitched roofs, and transitional roof applications

Pre-installation checks

Before fitting, confirm your roof structure uses F16 or F24 timber and verify your ventilation system is VELUX or a compatible standard system. Measure your roof opening to ensure the 78cm × 140cm flashing provides adequate coverage for your installation. Check that your roof type matches the flashing's application range: flat, pitched, or transitional. Inspect the roof area for any damage or deterioration that should be addressed before installation.

• Verify timber grade compatibility (F16 or F24)
• Confirm ventilation system compatibility with VELUX or standard systems
• Check roof type matches flashing application
• Inspect roof structure for damage before fitting

Pack contents and installation

Each pack contains one Twin and Combination Flashing unit sized 78cm × 140cm. The PVC construction ensures the flashing resists weather and UV exposure. The twin design allows you to connect to both sides of the ventilation opening simultaneously, streamlining the installation process. The ample dimensions reduce the risk of poor sealing or gaps during fitting.