An external screening arrangement for a roof window, the roof window having a window opening, a frame structure and a sash structure extending in parallel to the roof surface, each with top (3a, 4a) and bottom members (3d, 4d) and two mutually parallel side members (3b, 3c, 4b, 4c), where the screening arrangement comprises: a screening body having two side edges and a predefined length between a first end portion and a second end portion, said screening body being movable in a longitudinal direction between a non-screening position and a number of screening positions in which the screening body at least partially covers the window opening, the screening body comprising a screening cloth and a set of lamellas comprising a plurality of lamellas of which each lamella extends substantially from one side edge to the other of the screening body and defining a lamella length in the longitudinal direction of the screening body, a top casing configured to be rotatably connected to or fixed to the frame structure and to extend substantially in parallel with the top member of the frame, a roller shaft accommodated in the top casing and connected to drive means, the drive means being configured to rotate the roller shaft in a winding direction and an unwinding direction, the first end portion of the screening body being connected to the roller shaft such that the screening body is wound on the roller shaft in the non-screening position, a bottom profile extending substantially in parallel with the top casing between two ends and connected to the second end portion of the screening body, two side rails (21, 22) configured to extend substantially in parallel with a respective side member of the frame and sash structure in the mounted condition to guide at least the ends of the bottom profile, each side rail being at a first end fixedly or rotatably connected to the top casing and at a second end slidably and rotatably connected to the sash structure by means of a fitting, in the mounted condition of the screening arrangement, each lamella of the set of lamellas comprising a top element positioned on a first side of the screening cloth and a bottom element positioned on a second, opposite side of the screening cloth, characterised in that the top element and the bottom element are held together by means of a mechanical connection forming a releasable connection without the use of adhesion in the form of glue or bonding and comprising non-cloth penetrating, non-adhesive connection means, sandwiching the screening cloth between them, and allowing the top element and the bottom element to maintain their respective positions relative to the cloth, and that two adjacent lamellas of said set of lamellas are positioned at a distance (A, B) from each other, in the longitudinal direction of the screening body, exceeding the lamella length. a screening body having two side edges and a predefined length between a first end portion and a second end portion, said screening body being movable in a longitudinal direction between a non-screening position and a number of screening positions in which the screening body at least partially covers the window opening, the screening body comprising a screening cloth and a set of lamellas comprising a plurality of lamellas of which each lamella extends substantially from one side edge to the other of the screening body and defining a lamella length in the longitudinal direction of the screening body, a top casing configured to be rotatably connected to or fixed to the frame structure and to extend substantially in parallel with the top member of the frame, a roller shaft accommodated in the top casing and connected to drive means, the drive means being configured to rotate the roller shaft in a winding direction and an unwinding direction, the first end portion of the screening body being connected to the roller shaft such that the screening body is wound on the roller shaft in the non-screening position, a bottom profile extending substantially in parallel with the top casing between two ends and connected to the second end portion of the screening body, two side rails (21, 22) configured to extend substantially in parallel with a respective side member of the frame and sash structure in the mounted condition to guide at least the ends of the bottom profile, each side rail being at a first end fixedly or rotatably connected to the top casing and at a second end slidably and rotatably connected to the sash structure by means of a fitting, in the mounted condition of the screening arrangement, each lamella of the set of lamellas comprising a top element positioned on a first side of the screening cloth and a bottom element positioned on a second, opposite side of the screening cloth, characterised in that the top element and the bottom element are held together by means of a mechanical connection forming a releasable connection without the use of adhesion in the form of glue or bonding and comprising non-cloth penetrating, non-adhesive connection means, sandwiching the screening cloth between them, and allowing the top element and the bottom element to maintain their respective positions relative to the cloth, and that two adjacent lamellas of said set of lamellas are positioned at a distance (A, B) from each other, in the longitudinal direction of the screening body, exceeding the lamella length.