Fixing and buying guide

What this product is and who needs it

This flashing is an essential weatherproofing element for anyone installing VELUX windows or doors into a timber frame building. It sits between the window or door frame and the surrounding timber structure, preventing water from penetrating the building envelope. Builders, carpenters, and experienced DIY installers working on new timber frame construction or renovation projects will need this product to ensure a durable, watertight installation.

Sizing and compatibility

The flashing measures 78 × 98 cm and is suitable for roof pitches and timber frame applications up to 9m in length. Before ordering, confirm that your VELUX window or door frame is compatible with the MK04 flashing type, and measure your installation area to ensure this size will cover the perimeter adequately. The 4mm thickness is standard for this application and provides the necessary structural support without excessive weight.

• Check your VELUX window or door documentation to confirm MK04 flashing compatibility
• Measure the installation area to ensure 78 × 98 cm coverage is sufficient
• Verify your roof pitch falls within the product's design parameters
• Confirm your total installation length does not exceed 9m

Material and durability

The flashing is manufactured from FSC-certified birch plywood, confirming sustainable sourcing. It is treated with a boron-based preservative that resists rot and insect damage, making it suitable for long-term external use in the UK climate. The 4mm thickness balances durability with workability, allowing you to cut and fit the flashing around your window or door frame whilst maintaining structural integrity.

• FSC-certified birch plywood ensures responsible forestry sourcing
• Boron-based preservative treatment provides rot and insect resistance
• 4mm thickness offers structural strength and ease of installation
• Designed for external timber frame applications in exposed conditions

Pre-installation checks and preparation

Before fixing, inspect the flashing for any damage or warping during transport. Ensure the timber frame around your window or door opening is sound, dry, and level. Have your VELUX window or door frame ready for installation, along with appropriate fixings and sealants recommended by VELUX. Clear the installation area of debris and ensure you have adequate workspace. The flashing must be installed as part of a complete weatherproofing system, so do not attempt to use it in isolation.

• Inspect the flashing for transport damage before installation
• Confirm the timber frame is dry, level, and structurally sound
• Gather all VELUX-recommended fixings and sealants before starting
• Ensure the installation area is clean and free from debris
• Follow VELUX installation instructions for your specific window or door model