VELUX Flashings Guide

House roofing generally comprises the combination of a number of materials and surfaces aimed at maintaining a barrier between inside the house and the external weather. The hardest weather element to control is water since water is particularly invasive. Roof flashing is generally used as the final barrier against water penetration.

Flashing comprises the intersections and terminations of roofing systems and surfaces to prevent water penetration.


Roof flashing is generally installed around roof windows valleys, chimneys, eaves, rakes, skylights, ridges, and at roof to wall intersections. In all cases, effective flashing should resist all three drivers of water penetration: gravity, surface tension and wind pressure. As a result, flashing materials must be durable, low maintenance, weather resistant, able to accommodate movement and maintain compatibility with adjacent materials.

Roof flashing materials generally fall into one of two categories: membrane or sheetmetal. Commonly used roof flashing materials include aluminium, copper, lead-coated copper, lead, stainless steel, galvanized steel, zinc, and Galvalume.


VELUX Roof Window Flashings


As mentioned, flashings are required for roof windows. Roof window flashings come in grey aluminium as standard to match the window profile, with the options of copper, titanium zinc and coloured aluminium.

  • What is the pitch of the roof, ie. the angle of the roof's slope?
  • What is the existing roof made of? Eg. is the roof made of tile or slate?
  • How thick are the existing roof tiles?


The following table illsutrates which flashings will be required depending on your style of roof:-



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