How to Flash a flat roof window

22 Jan 2012
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United Kingdom
Hi all,

I have built my flat roof, and very soon need to fit and flash the Velux flat roof windows. There is no flashing kit for this, so I need to make one up from EDPM rubber (I have a roll of 300mm wide), and contact adhesive and seal.

I have never flashed a roof window before, and Google isn't very helpful. The install guide from Velux simply just shows this:


I think I need to first cur and install the lower edge, then the sides, then the top, so that the joints are the correct way. But how much should the joints lap over each other on the deck, and around the corners of the window unit?

Or, should there be a product to make this easier? Hertelan don't offer anything within the EDPM range.

Any help much appreciated!
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