Fixing and buying guide

What this product is and who needs it

This is a twin and combination flashing designed specifically for VELUX skylights of 78cm x 98cm dimensions. It is essential for anyone installing or replacing a VELUX skylight of this size, whether you are a professional installer or an experienced DIY builder. The flashing sits between the skylight frame and the roof structure, creating a weathertight barrier that is critical to the long-term performance of your installation.

Compatibility and sizing

This flashing is sized exclusively for VELUX skylights measuring 78cm x 98cm. It is compatible with timber structural grades F16, F24 and F32, covering the most common load-bearing timber specifications used in UK construction. Before ordering, confirm that your VELUX skylight matches these dimensions exactly and that your roof structure uses one of these compatible timber grades. Using the wrong size flashing will compromise the watertight seal.

• Size: 78cm x 98cm only
• Compatible timber grades: F16, F24, F32
• Check your skylight dimensions and roof timber grade before purchase

Material and durability

The flashing is manufactured from plastic with a powder coat finish, which delivers superior corrosion resistance and weathering protection. This finish is designed to withstand exposure to rain, UV light and temperature fluctuations, ensuring reliable performance throughout the service life of your skylight installation. The powder coat also provides a neat, professional appearance once installed.

Installation and pre-install checks

Before installation, inspect the flashing for any damage to the powder coat finish or cracks in the plastic. Ensure the roof opening is cut to the correct dimensions and that the surrounding timber structure is sound and level. The flashing must be positioned to overlap roof tiles or slates correctly to direct water away from the skylight frame. Follow VELUX installation instructions carefully to ensure the flashing is secured properly and bedded in appropriate sealant to maintain the watertight seal.

• Inspect flashing for damage before installation
• Verify roof opening dimensions match 78cm x 98cm
• Check that surrounding timber structure is level and sound
• Ensure correct overlap with roof covering material
• Use appropriate sealant to bed the flashing securely