A precast concrete step unit formed of left and right sidewalls, risers, and treads, wherein left and right sidewalls are assembled from a plurality of pre-cast sidewall panel modules, with a stepped panel module with two or more steps. Pre-cast concrete riser modules and tread modules extend between the right and left sidewalls. Reinforcing cross brace members are fastened to the inside distal surfaces of the left and right sidewalls where they are bolted into screw anchors embedded into the sidewalls. There are also screw anchor inserts embedded into the proximal ends of the sidewalls and into the ends of a first or lowest of the risers, and adapted for affixing the riser and sidewalls using clip angles or right-angle brackets. After alignment, the treads and remaining risers are installed using a construction adhesive which may be applied using a caulk gun. The precast modules each weight about 200 pounds or less, with none exceeding 250 pounds, and most much less. The installation can be carried out by an installation team of two workmen. One-piece concrete footing pieces can be used to support the lower edges of the sidewall panel modules.

A curved staircase including a double helix form with no center support column includes a plurality of stair segments, wherein each of the stair segments is formed from a plurality of rods coupled to a plurality of connecting nodes. The plurality of rods are arranged in a skewed tetrahedral geometry, which causes the plurality of stair segments to form a helical structure when the plurality of stair segments are coupled together. The plurality of rods form a spine on an underside of the plurality of stair segments. A tread is coupled to each of the stair segments. In alternate embodiments, the curved staircase may be formed from sheet metal creased to form a plurality of linear support locations and connecting nodes.

A curved staircase including a double helix form with no center support column includes a plurality of stair segments, wherein each of the stair segments is formed from a plurality of rods coupled to a plurality of connecting nodes. The plurality of rods are arranged in a skewed tetrahedral geometry, which causes the plurality of stair segments to form a helical structure when the plurality of stair segments are coupled together. The plurality of rods form a spine on an underside of the plurality of stair segments. A tread is coupled to each of the stair segments. In alternate embodiments, the curved staircase may be formed from sheet metal creased to form a plurality of linear support locations and connecting nodes.

A precast concrete step unit formed of left and right sidewalls, risers, and treads, wherein left and right sidewalls are assembled from a plurality of pre-cast sidewall panel modules, including at least one stepped panel module and at least one rectangular panel module. The panel modules are joined edge-to-edge at seams, with cement and/or with hardware. Pre-cast concrete tread modules extend at least between the left and right sidewalls and are mounted onto respective stepped edge surfaces of the right and left sidewalls. Pre-cast concrete riser modules also extending at least between the right and left sidewalls and mounted onto tread modules. These each extend vertically to successive stepped edge surfaces. Reinforcing cross brace members are fastened to the inward surfaces of the left and right sidewalls and extend at crossed diagonals between them. The precast modules each weight about 200 pounds or less and can be carried by two workmen. One-piece concrete footing pieces can be used to support the lower edges of the sidewall panel modules.

A precast concrete step unit formed of left and right sidewalls, risers, and treads, wherein left and right sidewalls are assembled from a plurality of pre-cast sidewall panel modules, including at least one stepped panel module and at least one rectangular panel module. The panel modules are joined edge-to-edge at seams, with cement and/or with hardware. Pre-cast concrete tread modules extend at least between the left and right sidewalls and are mounted onto respective stepped edge surfaces of the right and left sidewalls. Pre-cast concrete riser modules also extending at least between the right and left sidewalls and mounted onto tread modules. These each extend vertically to successive stepped edge surfaces. Reinforcing cross brace members are fastened to the inward surfaces of the left and right sidewalls and extend at crossed diagonals between them. The precast modules each weight about 200 pounds or less and can be carried by two workmen. One-piece concrete footing pieces can be used to support the lower edges of the sidewall panel modules.

A stair system according to one illustrative embodiment comprises: a support body mountable in a wall and comprising a connecting region; a stair body; and a mounting apparatus. The mounting apparatus comprises: a connector connectable to the connecting region of the support body in any one of a plurality of different positions in the connecting region of the support body; and a holder configured to hold the stair body such that when the connector is connected to the connecting region of the support body, the stair body is spaced apart from the support body to permit a wall panel between the stair body and the support body. Wall assemblies comprising such stair systems are also disclosed.

A stair system according to one illustrative embodiment comprises: a support body mountable in a wall and comprising a connecting region; a stair body; and a mounting apparatus. The mounting apparatus comprises: a connector connectable to the connecting region of the support body in any one of a plurality of different positions in the connecting region of the support body; and a holder configured to hold the stair body such that when the connector is connected to the connecting region of the support body, the stair body is spaced apart from the support body to permit a wall panel between the stair body and the support body. Wall assemblies comprising such stair systems are also disclosed.

A stair system according to one illustrative embodiment comprises: a support body mountable in a wall and comprising a connecting region; a stair body; and a mounting apparatus. The mounting apparatus comprises: a connector connectable to the connecting region of the support body in any one of a plurality of different positions in the connecting region of the support body; and a holder configured to hold the stair body such that when the connector is connected to the connecting region of the support body, the stair body is spaced apart from the support body to permit a wall panel between the stair body and the support body. Wall assemblies comprising such stair systems are also disclosed.

Level access structures including a first module and a second module. The first module includes first sidewalls defining a first open shaft with a first top end and a first bottom end opposite the first top end. The second module includes second sidewalls defining a second open shaft with a second top end and a second bottom end opposite the second top end. The second module is complementarily configured with the first level access module. The second module is configured to selectively couple to the first module with the second open shaft aligned with the first open shaft to define a continuous open shaft. The continuous open shaft is configured to contain a level access system.

Level access structures including a first module and a second module. The first module includes first sidewalls defining a first open shaft with a first top end and a first bottom end opposite the first top end. The second module includes second sidewalls defining a second open shaft with a second top end and a second bottom end opposite the second top end. The second module is complementarily configured with the first level access module. The second module is configured to selectively couple to the first module with the second open shaft aligned with the first open shaft to define a continuous open shaft. The continuous open shaft is configured to contain a level access system.