Fixing and buying guide

What this product is and who needs it

A twin and combination flashing is the weatherproofing interface that sits between your roof and the VELUX skylight frame. It bridges the gap created when a skylight penetrates the roof, directing water away from the frame and into the roof drainage system. You need this flashing if you are installing a new VELUX skylight or replacing an existing one. It is equally suitable for domestic loft conversions, garage roof lights, workshop ventilation, and commercial building installations.

Compatibility and sizing

This flashing is specifically engineered for VELUX skylights and measures 55 × 118 cm, which suits most standard VELUX skylight installations. Before purchasing, confirm that your skylight model is compatible with this size. Check your VELUX documentation or the existing flashing dimensions if you are replacing a unit. If your skylight is a non-standard size or a different manufacturer, this product may not be suitable.

• Size: 55 × 118 cm
• Material: Grade A timber with weather-resistant finish
• Designed for VELUX skylight frames
• Verify compatibility with your specific skylight model before ordering

Pre-installation checks and preparation

Before fixing, inspect the flashing for any damage to the timber or finish during delivery. Check that your roof opening dimensions match the flashing size and that the roof structure is sound and level. Ensure you have the correct roofing materials and sealants to hand, as the flashing must be bedded securely into the roof surface and sealed against the skylight frame to achieve a watertight joint. If you are replacing an old flashing, remove it completely and clean away old sealant and debris from the roof opening.

• Inspect timber and finish for transport damage
• Verify roof opening size matches 55 × 118 cm flashing
• Check roof structure is level and sound
• Remove old flashing and clean the roof opening thoroughly
• Gather roofing sealant and fixings before starting work

Installation and aftercare

The flashing must be positioned so that it sits flush with the roof surface and the skylight frame, creating a continuous weatherproof seal. Bed it into roofing cement or appropriate sealant and secure it according to your roof type and local building regulations. The Grade A timber and weather-resistant finish require no special maintenance, but inspect the seal annually to ensure it remains intact and free from cracks or gaps. In areas of heavy rainfall or extreme weather, check the flashing more frequently.