How and where to use guide
VELUX Twin and Combination Flashings 78x140cm EKL MK08 0021E
Typical applications and suitability
These flashings are specifically designed for sealing around chimneys, roof vents, and skylights on timber frame construction. They are suitable for use on roofs pitched between 30 and 60 degrees, which covers the majority of UK domestic pitched roofs. The 78 × 140cm dimensions make them appropriate for standard penetration sizes and extended coverage where needed. They are compatible with felt, metal, and tile roofing materials, allowing flexibility across different roof types. The FSC-certified softwood construction provides durability in harsh UK weather conditions.
- Chimneys, roof vents, and skylights on timber frame buildings
- Roof pitches from 30 to 60 degrees
- Compatible with felt, metal, and tile roofing
- Extended coverage up to 140cm length
- Domestic and light commercial applications
Installation and on-site guidance
Install flashings before final roofing material is laid where possible, ensuring the upper edge sits beneath the roofing material and the lower edge overlaps it. The flashing must be securely fixed to the timber frame around the penetration, with all joints sealed to prevent water ingress. Ensure the roof pitch falls within the 30–60 degree range for optimal performance. Check that the flashing sits flush against the penetration and roofing surface with no gaps. On felt roofs, bed the flashing in bitumen or appropriate adhesive. On tile or metal roofs, ensure proper overlap and secure fixing through the roofing material into the timber frame.
- Install upper edge beneath roofing material, lower edge overlapping it
- Secure firmly to timber frame around the penetration
- Seal all joints to prevent water ingress
- Verify roof pitch is between 30 and 60 degrees
- Ensure flush contact with no gaps at penetration or roofing surface
Maintenance and durability
FSC-certified softwood flashings require periodic inspection to maintain their watertight performance. Check annually for signs of movement, gaps, or deterioration, particularly after severe weather. Inspect joint seals and re-seal if necessary using appropriate roofing sealant. Keep gutters and roof surfaces clear of debris to prevent water pooling around the flashing. The timber will weather naturally over time; this is normal and does not affect performance if the seal remains intact. Do not paint or treat the flashing unless using products specifically approved for use on roofing flashings, as this may compromise the seal.
- Inspect annually for gaps, movement, or deterioration
- Check and reseal joints with appropriate roofing sealant as needed
- Keep roof surface and gutters clear of debris
- Natural weathering of timber is normal and does not affect performance
- Do not paint or treat unless using roofing-approved products
Limitations and important considerations
These flashings are designed specifically for roof pitches between 30 and 60 degrees; use outside this range may compromise the watertight seal and is not recommended. The 78 × 140cm size is fixed and may require cutting or joining for non-standard penetrations; ensure any modifications maintain the integrity of the seal. Flashings are not suitable for flat roofs or pitches below 30 degrees. Ensure the timber frame is sound and properly prepared before installation. Do not install on damaged or deteriorating roofing materials; repair the roof surface first. These are timber-based products and should be stored dry before installation to prevent warping.
- Not suitable for roof pitches below 30 degrees or above 60 degrees
- Fixed size may require modification for non-standard penetrations
- Not suitable for flat roofs
- Requires sound, properly prepared timber frame
- Store dry before installation to prevent warping