The object of the invention is a sandwich panel (1) comprising a mineral wool core (2) placed between and fixed to a first shell element (7a) and a second shell element (7b), wherein each shell element in one end of the panel (1) is formed into or is provided with a tongue or groove (3a, 3b or 8a, 8b), and in the opposite end of the panel (1) is formed into or provided with a tongue or groove (3a, 3b or 8a, 8b). At least one of said two shell elements (7a, 7b) is in at least one of the ends of the panel, where the shell element is not formed into or provided with a tongue or groove (3a, 3b or 8a, 8b), provided with a waterproof and concurrently vapor permeable band (6), which partly is fixed (6a) on top of the shell element (7b) such that it covers the shell element (7b) in a longitudinal area extending along the edge of the entire shell element and in addition at least some way over at least one of the tongues or grooves and which partly has a freestanding portion (6b) extending along said longitudinal area
