Method for enlarging the volumetric load space of a cabin of a vehicle comprising the following steps: - arranging a vehicle of the van type with an interior cabin comprising a front driver's cabin, an intermediate passenger cabin and a rear cargo cabin; said interior cabin being bounded at the front by a bonnet area for housing the engine, at the sides by a first and second side wall (12,13), at the bottom by an underbody, at the top by a roof and at the rear by a hatch; said hatch being openable and closable by a first hinge connection with the roof; said roof having within it a first, a second reinforcing bar (141, 142) and being the first bar, crossing the vehicle transversely from a first sidewall to a second side wall, located in an intermediate position between the front driver's cabin and the intermediate passenger cabin, and being the second bar, crossing the vehicle transversely from a first to a second side wall (12,13), placed in an intermediate position between the intermediate passenger cabin and the rear cargo cabin; - cutting the roof of the vehicle in order to obtain on the same an opening obtained by means of a first pair of cutting lines (31,32), parallel to each other and extending from the rear cargo cabin to the intermediate passenger cabin, and a second cutting line, substantially transversal with respect to the first pair of cutting lines (31,32) and made between the front driver's cabin and the intermediate passenger cabin; said opening being made while leaving the hatch intact; - providing a covering element having a concave box shape and having a top wall, substantially quadrangular in shape, from which develop a pair of side walls connected to each other at the front with a spoiler wall and at the rear with a rear wall; said rear wall being connected to the top wall by a second hinge connection; said covering element being internally provided with a first pair of uprights, placed in an intermediate position with each upright respectively close to a side wall, and with a second pair of uprights, placed in a position close to the rear wall with each upright respectively also close to a side wall; - coupling the covering element to the roof of the vehicle by placing it with the concavity facing the roof of the vehicle; this coupling being of the fluid-tight type; characterised by the fact that said coupling phase includes a sub-phase of joining the rear wall of the covering element to the hatch of the vehicle, making the two elements integral so that, when the hatch of the vehicle is opened or closed, the rear wall of the covering element is opened or closed at the same time. - arranging a vehicle of the van type with an interior cabin comprising a front driver's cabin, an intermediate passenger cabin and a rear cargo cabin; said interior cabin being bounded at the front by a bonnet area for housing the engine, at the sides by a first and second side wall (12,13), at the bottom by an underbody, at the top by a roof and at the rear by a hatch; said hatch being openable and closable by a first hinge connection with the roof; said roof having within it a first, a second reinforcing bar (141, 142) and being the first bar, crossing the vehicle transversely from a first sidewall to a second side wall, located in an intermediate position between the front driver's cabin and the intermediate passenger cabin, and being the second bar, crossing the vehicle transversely from a first to a second side wall (12,13), placed in an intermediate position between the intermediate passenger cabin and the rear cargo cabin; - cutting the roof of the vehicle in order to obtain on the same an opening obtained by means of a first pair of cutting lines (31,32), parallel to each other and extending from the rear cargo cabin to the intermediate passenger cabin, and a second cutting line, substantially transversal with respect to the first pair of cutting lines (31,32) and made between the front driver's cabin and the intermediate passenger cabin; said opening being made while leaving the hatch intact; - providing a covering element having a concave box shape and having a top wall, substantially quadrangular in shape, from which develop a pair of side walls connected to each other at the front with a spoiler wall and at the rear with a rear wall; said rear wall being connected to the top wall by a second hinge connection; said covering element being internally provided with a first pair of uprights, placed in an intermediate position with each upright respectively close to a side wall, and with a second pair of uprights, placed in a position close to the rear wall with each upright respectively also close to a side wall; - coupling the covering element to the roof of the vehicle by placing it with the concavity facing the roof of the vehicle; this coupling being of the fluid-tight type;