Fixing and buying guide

What this product is and who it is for

Twin and combination flashings are essential sealing components that sit between a roof window frame and the roof structure, preventing water ingress at the point where the window penetrates the roof. These flashings are designed for pitched roof installations in the UK where reliable weather protection is critical. They suit experienced DIY installers and professional roofers working on new builds or retrofit installations.

Compatibility and sizing

This 134x140cm flashing is sized for standard UK roof window openings and roof configurations. Before purchase, confirm that your roof pitch falls within the 30° to 90° range and that your roof structure uses timber graded F16, F24, or F36. Check your roof window specifications and opening dimensions against the 134x140cm size to ensure correct fit. Incorrect sizing or pitch will compromise the weather seal.

• Suitable roof pitch: 30° to 90°
• Compatible timber grades: F16, F24, F36
• Size: 134 x 140cm
• Material: Vinyl-coated polyester

Pre-installation checks

Before fixing, verify that your roof structure and timber grades match the product specification. Inspect the roof opening to confirm dimensions align with the 134x140cm flashing. Check that the roof pitch is within the 30° to 90° range using a pitch gauge or architectural drawings. Ensure the roof surface is clean and free from debris, and that you have appropriate fixings and sealants suitable for vinyl-coated polyester materials. Have a clear understanding of the installation sequence, as these flashings must be positioned correctly relative to roof covering materials to achieve a proper weather seal.

• Confirm roof pitch is between 30° and 90°
• Verify timber grades are F16, F24, or F36
• Check opening dimensions match 134x140cm size
• Inspect roof surface condition and cleanliness
• Gather appropriate fixings and compatible sealants before starting

Installation suitability

These flashings are suitable for experienced DIY installers and professional contractors. Installation requires understanding of roof construction, correct positioning relative to roof coverings, and proper sealing techniques. If you are unfamiliar with roof window installation or roof sealing, consult a qualified roofer or the VELUX installation documentation. Incorrect installation will result in water ingress and potential structural damage.