Chassis with raised rear floor and method of assembly

A method for assembling constituent elements of a motor vehicle chassis comprising:

• providing a lower chassis part, the lower chassis part comprising two longitudinal members covered at the front by two plates forming lateral floor reinforcements and comprising a rear central crossmember joining the longitudinal members and flush in the region of the lateral floor reinforcements, the lateral reinforcements having an internal edge comprising a welding strip;
• assembling a raised floor area on the lower part, forming both a seat and a housing for an energy storage tank, by fixing by welding to the two lateral floor reinforcements a raiser plate forming a transverse reinforcement between the two lateral reinforcements, by fixing by welding to the rear central crossmember a rear raiser part, by fixing by welding two plates forming lateral raiser parts, each along one of the welding strips of a lateral reinforcement, and by assembling a plate forming a seat-cushion support of the floor by welding to the two lateral raiser parts, to the rear raiser part and to the transverse reinforcement, above the three raiser parts and above the transverse reinforcement.