A plurality of wall cells rest upon an underlying cementitious foundation and form a perimeter of the vault. Each wall cell has two lateral sides with mating surfaces thereon which are of complementary undulating shape with adjacent lateral surfaces of adjacent wall cells. The wall cells have different thicknesses and widths to provide desirable wall thickness for a different portions of the oncology vault. A door assembly formed of specialized wall cells and with a pivoting door element are also included within the wall. A ceiling is provided above space inboard of the wall cells. This ceiling is formed of separate ceiling slab elements. The slabs are stacked in at least one layer. In one embodiment, multiple layers of slabs are stacked with seams between slabs of each layer offset from each other. In another embodiment, lateral sides of the slabs have a complementary undulating shape.

A rectangular block having a front surface, a rear surface, a bottom surface, a top surface defined by a pair of lengthwise edges and a pair of side edges connecting the lengthwise edges, the rectangular block including: a first channel disposed along a left side surface, the first channel extending in a direction from the front surface to the rear surface; and a second channel along a plane parallel to the left side surface, the plane disposed at an offset distance from the left side surface, the second channel extending in a direction from the front surface to the rear surface, wherein the left side surface is configured to be positionable so as to mate with a left side surface of an adjacently disposed block to form a full channel to receive a rebar, whereby walls are constructible from a plurality of such blocks.

A building block system of a plurality of transportable, lightweight, and reusable hollow prefabricated non-masonry interlocking mortarless building blocks that have corresponding mating formations being protuberances and concavities that run vertically up the building blocks being joined together and when aligned in a staggered manner upwardly are held together with threaded reinforcement rods extending vertically between and connected to the top and bottom channels through connectable couplings and capped off with complementary cap attachments.

A building block system of a plurality of transportable, lightweight, and reusable hollow prefabricated non-masonry interlocking mortarless building blocks that have corresponding mating formations being protuberances and concavities that run vertically up the building blocks being joined together and when aligned in a staggered manner upwardly are held together with threaded reinforcement rods extending vertically between and connected to the top and bottom channels through connectable couplings and capped off with complementary cap attachments.

A construction element includes at least one module with a rectangular parallelepiped shape, hollow and made of a composite material. The module is delimited by an enclosure with four panels, two first opposing parallel panels and two second panels perpendicular to the first panels. The second panels include at least one groove parallel to the first panels. Each second panel is extended on one side by an L-shaped profile and on the other side by a flat profile. The profiles are elements protruding outwards, parallel to the groove.

A construction element includes at least one module with a rectangular parallelepiped shape, hollow and made of a composite material. The module is delimited by an enclosure with four panels, two first opposing parallel panels and two second panels perpendicular to the first panels. The second panels include at least one groove parallel to the first panels. Each second panel is extended on one side by an L-shaped profile and on the other side by a flat profile. The profiles are elements protruding outwards, parallel to the groove.