Step-block precast stair

A construction unit comprising:

• a wall system having a plurality of T-shaped wall blocks arranged in a plurality of horizontal courses in Flemish bond, each of the T-shaped wall blocks having a main body portion, a side body portion and first and second intersecting corners, the main body portion having a rectangular cross section, a central portion, a first arm and a second arm extending horizontally from the central portion in opposing directions,
• wherein:
• the side body portion has a square cross section emanating vertically from the central portion;
• the first and second intersecting corners are disposed between the main body portion and the side body portion on both sides of the side body portion;
• each of the T-shaped wall blocks, through the first and second arms, connects securely with the intersecting corners of two adjacent T-shaped wall blocks that are in the opposite orientation in the horizontal courses so that alternate T-shaped blocks in the horizontal courses have rectangular side surfaces and square side surfaces facing outward and square side surfaces in a first horizontal course are disposed in the middle of rectangular side surfaces of a second horizontal course below the first horizontal course;
• and
• a stair system having a plurality of precast concrete steps, each of the precast concrete steps including a generally horizontal tread portion, a riser portion connected integrally to the tread portion and a T-shaped connecting portion connected integrally to the tread portion and the riser portion, the T-shaped connecting portion having dimensions equal to the T-shaped wall blocks, each of the precast steps being installed by substituting a T-shaped wall block having the rectangular side surface outward with the T-shaped connecting portion so that the tread portion and the riser portion project perpendicularly out of the wall system.