How and where to use guide
VELUX Twin and Combination Flashings 94x140cm EBL PK08 0021B
Suitable applications and roof specifications
These flashings are designed for pitched roof installations where roof windows or multiple roof penetrations need a secure, weather-resistant seal. They are compatible with softwood timber grades F16, F24 and F36, which are standard structural timbers used in UK roof construction. The flashings work effectively on roof pitches between 30 and 60 degrees; outside this range, water drainage and seal integrity may be compromised. The 140cm maximum length means they can accommodate twin window installations or combination penetrations within this dimension.
- Suitable for roof pitches 30–60 degrees only
- Compatible with timber grades F16, F24 and F36
- Maximum installation length 140cm
- Designed for both single and multiple roof penetrations
Installation and on-site use
Install the flashings where the roof window frame or penetration meets the roof surface, ensuring the vinyl material sits flush against both the window frame and the roof slope. The vinyl construction provides a durable, weather-resistant barrier that must be properly seated to prevent water pooling or wind-driven rain bypass. Position the flashing so that the upper edge is tucked under the roof covering above the penetration and the lower edge overlaps the roof covering below, following the natural water run-off direction down the pitch. Secure according to the window manufacturer's instructions and ensure all joints are sealed to prevent water ingress at the edges.
- Position upper edge under roof covering above the window
- Ensure lower edge overlaps roof covering below the window
- Seat vinyl material flush against frame and roof slope
- Seal all joints and edges to prevent water bypass
- Follow roof pitch direction for water drainage
Maintenance and durability
The vinyl construction offers long-term weather resistance without the need for regular treatment or repainting. Inspect the flashing annually, particularly after severe weather, to ensure the seal remains intact and no debris has accumulated around the edges. Check that the overlap with roof covering has not shifted and that no gaps have opened at joints. Clear any moss, lichen or debris that may trap moisture against the vinyl. The durable vinyl material resists UV degradation and temperature cycling typical of UK roof environments.
- Inspect annually for seal integrity and debris
- Clear moss, lichen and debris from edges
- Check overlaps remain secure after severe weather
- No painting or treatment required
Limitations and important considerations
These flashings are designed specifically for roof pitches between 30 and 60 degrees; installation outside this range will not provide adequate weather protection. The 94 × 140cm size is fixed and cannot be cut or extended, so measure your penetration length carefully before ordering. The flashings are designed for use with the specified timber grades; use on other materials or grades may compromise the seal. Installation must follow the window manufacturer's instructions to ensure warranty validity and proper performance. These flashings are not suitable for flat roofs or pitches below 30 degrees where water drainage cannot be guaranteed.
- Not suitable for roof pitches below 30 degrees or above 60 degrees
- Fixed size 94 × 140cm; cannot be cut or extended
- For use with F16, F24 and F36 timber grades only
- Installation must follow window manufacturer's instructions