Flashing device and a method of mounting a flashing device at a roof window

A method of mounting a flashing device at a roof window comprising a frame and mounted in a roof structure, comprising the following steps:

• A) providing a flashing device comprising a first flashing member and a second flashing member both extending in a length direction of the flashing device, and two sealing members arranged at opposite ends of the flashing device seen in the length direction, where an upwards portion of the first flashing member and a downwards portion of the second flashing members are interconnected in sliding engagement allowing the relative position between the first and second flashing members to be adjusted during mounting of the flashing device, where the first flashing member further comprises a outward portion extending at an angle in relation to the upwards portion and being configured for extending over the roof structure away from the roof window, where the second flashing member further comprises an inward portion extending at an angle in relation to the downward portion and being configured for engagement with the frame of the roof window, and where each sealing member includes a first sealing portion and a second sealing portion, said first sealing portion being positioned substantially in parallel with the inward portion and said second sealing portion being positioned substantially in parallel with the downward portion, characterized in that the sealing member further comprises at least one frame attachment portion configured for attachment of the sealing member to the frame of the roof window, where the at least one frame attachment portion comprises a flange extending from the first sealing portion and being configured for sliding engagement with a groove in the frame and where the flange comprises a first flange leg extending from the first sealing portion away from the second sealing portion and a second flange leg extending substantially perpendicular to the first flange leg and substantially in parallel with the first sealing portion,
• B) arranging the flashing device on the roof structure and at an outer side of the frame of the roof window facing away from a frame opening defined by the frame,
• C) connecting the sealing member to the frame using the at least one frame attachment portion.