A seal is installed to a seal supporting surface of a vehicle pillar structure. A door assembly has an inner panel and a window sash section with an attachment area at an intersection between the inner panel and the window sash section. A trim panel has a main body covering at least a portion of an inboard surface of the inner panel and a flange that extends along an upright edge of the main body. The flange has an upper end covering the attachment area and a lower end of the window sash section. The window sash section and the flange define a sealing surface extending from an upper end of the door assembly to a lower end of the door assembly. The seal contacts the sealing surface with the door assembly in the closed position.