Fixing and buying guide

What this product is and who needs it

This underfelt collar is a flashing component that sits beneath the roof covering at the point where a VELUX roof window or Sun Tunnel penetrates the roof structure. It creates a weather-tight seal and directs water away from the opening. You need this collar if you are installing a compatible VELUX roof window or Sun Tunnel system in either a new build property or during a refurbishment project. It is a professional-grade component that forms part of the complete VELUX installation system.

Compatibility and sizing

This collar is sized at 780 × 1400mm and is designated as BFX MK08 1000. It is compatible with standard VELUX roof window and Sun Tunnel ranges. Before ordering, confirm that your VELUX window or Sun Tunnel model matches the MK08 specification. Check your product documentation or contact VELUX technical support if you are unsure which collar size your installation requires, as using an incorrectly sized collar will compromise the weather-tight seal.

• Collar dimensions: 780 × 1400mm
• Product code: BFX MK08 1000
• Verify compatibility with your specific VELUX window or Sun Tunnel model before purchase

Installation and preparation

This collar is designed for installation during new build construction or refurbishment work. It must be positioned at the roof penetration point before the roof covering is laid, allowing the underfelt and transverse drainage gutter to function correctly. The integrated drainage gutter directs water laterally away from the window opening, protecting the installation from weather damage. Proper positioning and securing of the collar is critical to achieving a weather-tight seal that will perform reliably over the long term.

• Install before roof covering is applied
• Position the collar at the roof penetration point
• Ensure the transverse drainage gutter is clear and unobstructed
• Follow VELUX installation guidance for your specific window or Sun Tunnel model

Pre-installation checks

Before fitting, inspect the collar for any damage sustained during delivery or storage. Verify that the underfelt collar and drainage gutter are intact and free from debris. Confirm that the roof opening dimensions and structure are compatible with the 780 × 1400mm collar size. Check that you have all other required components for your VELUX installation system, as this collar is one element of a complete assembly. Ensure the roof structure is prepared and ready to receive the collar at the correct stage of your build or refurbishment project.