The method involves rotatably gluing joint sealing tapes (3) on frame profiles before installing a frame (4). A window frame is inserted into a window opening and connected with a masonry part. Parts of the joint between window or door frames and building structure are sealed by bituminous layer made of painting, trajectories or homogeneous materials. Mountable metal sheets (1) are attached to the frame to which end regions of the bituminous layer adheres. The ends of the bituminous layer are connected with the metal sheets. An independent claim is also included for a mountable metal sheet.
