Fixing and buying guide

What this product is and who needs it

This is a PVC flashing kit engineered to seal the gap between a VELUX skylight and your timber roof structure. It prevents water ingress and protects against wind-driven rain penetration at the critical junction where the skylight frame meets the roof. You need this flashing if you are installing a new VELUX skylight, replacing an existing flashing, or carrying out retrofit work on a timber roof. The twin and combination design provides flexibility for different installation scenarios and roof configurations.

Compatibility and sizing

This flashing is designed for VELUX skylights with a maximum size of 78cm × 118cm. It is compatible with timber roof construction using structural grades F16, F24, and F36. Before purchasing, confirm your skylight dimensions and check that your roof timber meets one of these grades. If your skylight exceeds these dimensions or your timber grade differs, you will need a different flashing specification. The flashing integrates with standard VELUX skylight kits but can also be used as a standalone component for replacement or retrofit applications.

• Maximum skylight size: 78cm × 118cm
• Compatible timber grades: F16, F24, F36
• Material: PVC
• Suitable for new installations, replacements, and retrofit work

Pre-installation checks

Before fitting, verify that your VELUX skylight dimensions fall within the 78cm × 118cm maximum size and that your roof timber is graded F16, F24, or F36. Inspect the roof structure around the installation area for any damage, rot, or structural weakness that must be addressed before flashing installation. Ensure the roof opening is clean and free from debris. Check that you have all components in your flashing kit and that the PVC material is undamaged. Have appropriate tools ready for on-site adjustment and fixing, as the twin and combination design allows for straightforward fitting but requires careful alignment to achieve a weather-tight seal.

• Confirm skylight size and timber grade compatibility
• Inspect roof structure for damage or weakness
• Clean the roof opening thoroughly
• Check all flashing components are present and undamaged
• Prepare tools for on-site adjustment and fitting

Installation overview

The twin and combination design of this flashing allows for straightforward installation with on-site adjustment. Position the flashing around the skylight frame to create a secure, weather-tight seal. The combination design delivers robust protection against wind-driven rain ingress. Follow the alignment carefully to ensure the flashing sits correctly against both the skylight frame and the roof structure. The PVC material can be adjusted on site to accommodate minor variations in roof pitch or structure. Once positioned correctly, secure the flashing according to the installation instructions provided with your VELUX skylight kit. Proper sealing at this junction is critical to prevent water penetration and maintain the integrity of your roof.