Fixing and buying guide

What this product is and who needs it

This is a purpose-made flashing kit for VELUX roof windows being installed into slate tile roofing. It is essential if you are fitting a roof window into an existing slate roof or new slate tile installation. The integrated 3-in-1 design means you receive the flashing, thermal insulation collar, and underfelt collar as one unit, eliminating the need to source and fit these components separately on site.

Compatibility and sizing

This flashing is compatible with VELUX roof windows and is specifically engineered for slate tile applications. It will work with slate tiles up to 8mm in thickness. The 188mm × 118mm dimensions suit standard roof window openings. Before ordering, confirm your roof window model and measure your slate tile thickness to ensure this product matches your requirements. If your slate exceeds 8mm or your window opening differs from these dimensions, you will need an alternative flashing kit.

• Maximum slate tile thickness: 8mm
• Flashing dimensions: 188mm × 118mm
• Includes BDX 2000 insulation collar and BFX underfelt collar
• Grey finish suitable for most slate roof colours

What is included and pre-installation checks

You receive one complete 3-in-1 flashing unit ready to install. The integrated design means all three components—flashing, insulation collar, and underfelt collar—are supplied as a single assembly. Before installation, verify that your slate tiles are 8mm or thinner, check that the roof window opening matches the 188mm × 118mm dimensions, and ensure the roof structure is sound and properly prepared. Inspect the flashing for any damage in transit and confirm it matches your roof window model.

• Single integrated 3-in-1 unit—no separate collar assembly required
• Confirm slate thickness does not exceed 8mm
• Verify roof window opening dimensions match 188mm × 118mm
• Check roof structure is sound before fitting

Installation benefits

The 3-in-1 integrated design reduces installation time and complexity on site. Because the flashing, insulation collar, and underfelt collar are combined into one unit, you handle fewer components and eliminate multiple assembly steps. This also reduces material waste and the risk of missing or misaligning individual collar elements. The BDX 2000 insulation collar is built in, ensuring consistent thermal performance around the window opening.

• Fewer on-site assembly steps
• Reduced material handling and waste
• Thermal insulation integrated into the flashing
• Consistent performance with no missing components