Fixing and buying guide
VELUX Underfelt Collar 94x160cm BFX PK10 1000
What this product is and who needs it
The underfelt collar is an essential flashing component for anyone installing or replacing VELUX roof windows or Sun Tunnels. It sits between the window frame and the roof structure, providing a weather-tight seal that prevents water penetration and wind infiltration. The integral drainage gutter channels water safely away from the frame. This product is suitable for both new build installations and refurbishment work, making it essential for roofers, builders, and serious DIY installers working with VELUX systems.
- Weather-tight flashing collar with integral transverse drainage gutter
- Designed for VELUX roof windows and Sun Tunnel systems
- Pack of 10 units – ideal for multiple installations
- Suitable for new build and refurbishment projects
Compatibility and sizing
This underfelt collar is compatible with standard VELUX roof window and Sun Tunnel ranges. The 940 x 1600mm dimensions are the industry standard size for these systems. Before ordering, confirm that your VELUX windows or Sun Tunnels use the BFX collar specification. Check your product documentation or contact VELUX technical support if you are unsure whether this collar matches your specific window model or installation.
- Dimensions: 940 x 1600mm
- Compatible with standard VELUX roof window ranges
- Compatible with VELUX Sun Tunnel systems
- Verify compatibility with your specific window model before purchase
Pack contents and preparation
Each pack contains 10 underfelt collars, providing enough for multiple window installations. Before fitting, inspect all collars for damage in transit and ensure you have the correct size for your windows. Lay out the collars and familiarise yourself with the drainage gutter orientation – this must face downslope to function correctly. Have your roof opening prepared to the correct dimensions and ensure the roof structure is clean and dry before installation begins.
- Pack quantity: 10 underfelt collars
- Inspect for transit damage before use
- Confirm drainage gutter orientation before fitting
- Ensure roof opening is clean and dry
Pre-installation checks
Before fixing the collar, verify that your roof opening matches the 940 x 1600mm collar dimensions and that the VELUX window frame is ready for installation. Check that you have all necessary fixings and sealants specified by VELUX for your roof type and pitch. Ensure weather conditions are suitable – avoid installation in heavy rain or high winds. Confirm that the roof structure can support the window assembly and that any structural work has been completed. Have your installation instructions for the specific VELUX window model to hand, as the collar must be fitted in the correct sequence with the window frame and roof membrane.
- Verify roof opening dimensions match 940 x 1600mm collar size
- Confirm VELUX window frame is ready for installation
- Check you have correct fixings and sealants for your roof type
- Ensure roof structure is sound and prepared
- Have VELUX window installation instructions available