Fixing and buying guide

Who this is for and what it does

This flashing is for builders, roofers, and serious DIY customers installing or replacing VELUX roof ventilators. It creates a watertight seal around the ventilator unit where it penetrates the roof, preventing water damage to the roof structure and interior whilst allowing the ventilator to function correctly. The flashing is a critical weatherproofing component and must be fitted correctly to avoid leaks.

Compatibility and sizing

This flashing is sized at 134 × 98 cm and is designed specifically for VELUX roof ventilator units. It is compatible with timber roof structures graded F16, F24, and F36. The product suits roof pitches between 30 and 60 degrees; if your roof pitch falls outside this range, a different flashing type will be required. Confirm your ventilator model and roof pitch before purchase to ensure correct fit.

• Dimensions: 134 × 98 cm
• Roof pitch range: 30–60 degrees
• Compatible timber grades: F16, F24, F36
• Designed for VELUX roof ventilators only

Pre-installation checks

Before fitting, verify that your VELUX ventilator unit is compatible with this flashing size and that your roof pitch falls within the 30–60 degree range. Inspect the roof structure to confirm timber grade and check that the area around the ventilator opening is sound and free from rot or damage. Ensure you have the correct flashing for your specific ventilator model, as VELUX produces different flashings for different units.

• Check roof pitch is between 30 and 60 degrees
• Confirm timber grade is F16, F24, or F36
• Verify VELUX ventilator model compatibility
• Inspect roof structure for damage before installation

Installation overview

The twin and combination design allows straightforward installation and adjustment to suit your specific roof pitch and angle. The flashing should be positioned around the ventilator opening and secured to create a complete watertight seal. Follow VELUX installation instructions carefully to ensure proper sealing and weatherproofing. The combination style accommodates the range of roof pitches within the 30–60 degree specification, reducing the need for multiple flashing types on varied roof geometries.