Roof structure for vehicle

A vehicle comprising a roof structure, wherein the roof structure comprises:

• a main roof module as a fixed module element including a main roof panel;
• an extension roof module as a variable module element that is connected to a rear of the main roof module along a vehicle body front-back direction and includes an extension roof panel;
• a roof module mounting portion at the rear of the main roof panel;
• and
• a drain path disposed at a connection between the main roof panel and the extension roof panel, wherein the drain path comprises:
• a main drain flange section extending in a first downward step from a rear end of the main roof panel, wherein the main drain flange section is fluidly connected to the roof module mounting portion, and
• an extension drain flange section extending in a second downward step from a front end of the extension roof panel and connected to the main drain flange section, wherein the main drain flange section and the extension drain flange section overlap each other in a vertical direction, wherein the main drain flange section and the extension drain flange section are disposed along a vehicle width direction.

A method of assembling a vehicle, comprising:

• assembling a main roof unit including a main roof panel, main transverse direction roof rails, a bridge roof rail, and main longitudinal direction roof rails, wherein the main roof panel includes a main drain flange section recessed at a rear end of the main roof panel, wherein the main roof panel includes a roof module mounting portion at a rear end portion of the main roof panel, and wherein the assembling of the main roof unit comprises:
• connecting the main longitudinal direction roof rails to the main transverse direction roof rails and the bridge roof rail along a vehicle body front-back direction, and
• connecting the main roof panel to the main transverse direction roof rails, the bridge roof rail, and the main longitudinal direction roof rails;
• selecting a usage type of the vehicle;
• selecting and assembling an extension roof unit including an extension roof panel, an extension transverse direction roof rail, and extension longitudinal direction roof rails, based on the selecting of the usage type of the vehicle, wherein the extension roof panel includes an extension drain flange section recessed at a front edge of the extension roof panel, wherein the assembling of the extension roof unit comprises:
• connecting the extension transverse direction roof rail to the extension longitudinal direction roof rails, and
• connecting the extension roof panel to the extension transverse direction roof rail and the extension longitudinal direction roof rails;
• overlapping and welding the main drain flange section and the extension drain flange section to form a drain path extending along a vehicle width direction, such that the roof module mounting portion is fluidly connected to the drain path;
• connecting the extension longitudinal direction roof rails to the bridge roof rail and the extension transverse direction roof rail along the vehicle body front-back direction;
• and
• attaching the main transverse direction roof rails, the bridge roof rail, and the extension transverse direction roof rail to upper portions of side structures of the vehicle.