Fixing and buying guide

What this product is and who needs it

This flashing is a weatherproofing component that sits between your VELUX roof vent and the surrounding roof tiles or slates. It prevents water ingress at the critical junction where the vent penetrates the roof. The twin and combination design means a single flashing can be configured to suit different roof layouts and vent positions, reducing the need to stock multiple flashing types.

Compatibility and sizing

This 55 × 98 cm flashing is engineered for VELUX roof vents and is compatible with FSC 184 timber grades or equivalent. It is rated for roof pitches up to 30 degrees; if your roof pitch exceeds 30 degrees, you will need a different flashing specification. Before ordering, confirm your roof pitch and that your timber frame meets FSC 184 standards or equivalent.

• Size: 55 × 98 cm
• Maximum roof pitch: 30 degrees
• Timber grade: FSC 184 or equivalent
• Material: UV-stabilised PVC

Pre-installation checks

Inspect your roof vent opening and surrounding timber to ensure they are in good condition and free from rot or damage. Verify your roof pitch does not exceed 30 degrees using a pitch gauge or spirit level. Check that the vent frame is square and level before fitting the flashing. Ensure you have adequate roof space around the vent opening to accommodate the full 55 × 98 cm flashing without obstruction from rafters, joists, or other structural elements.

• Confirm roof pitch is 30 degrees or less
• Inspect timber for rot or structural damage
• Check vent frame is square and level
• Verify sufficient space around the vent opening

Installation and fixing

The twin and combination design allows you to configure the flashing to suit your specific roof layout. Position the flashing around the vent opening, ensuring it sits flush against the roof surface and timber frame. The PVC material is durable and UV-stabilised, so it will not degrade under sun exposure. Secure the flashing according to VELUX installation guidance, using appropriate fixings for your roof type. Ensure all edges are sealed to prevent water penetration, and check that the flashing sits correctly under the upper roof tiles or slates and over the lower ones to direct water away from the vent opening.