A method for constructing a multi-story building having floor shelves to support floors, comprising: assembling a plurality of wall trusses, each consisting of a plurality of vertical members (101 - 105), adjacent ones of which are interconnected at the top and bottom by horizontal beams (111 - 114, 121 - 124), spanning the space between adjacent vertical members and connected to a respective side of the vertical members (101 - 105), the interconnection being fixed joints, wherein at least two vertical members (101 - 105) of the wall truss comprise hollow columns (301 - 309, 311-319); for at least two floors of the multi-story building: inserting a mating member (341 - 350) into the hollow columns (301 - 309, 311-319) of at least two of the vertical members for each wall truss (1, 2) and additional wall truss (3, 4), where the mating member (341 - 350) extends into both the hollow columns (301 - 309) of each wall truss (1, 2) and the hollow columns (311 - 319) of the additional wall truss (3, 4); affixing floor shelves, each including an upper horizontal element, on a top horizontal beam of a wall truss, wherein the floor shelf also includes a substantially planar surface extending in a horizontal direction perpendicular to the horizontal beam to which it is affixed into the interior of the multi-story building; and stacking additional wall trusses (3, 4) on top of the plurality of wall trusses (1, 2) installed for the floor below, by setting the bottom of the hollow columns of the vertical members (311 - 319) of a set of wall trusses (3, 4) on the vertical members (301 - 309) of the existing wall trusses (1, 2) of the floor below. assembling a plurality of wall trusses, each consisting of a plurality of vertical members (101 - 105), adjacent ones of which are interconnected at the top and bottom by horizontal beams (111 - 114, 121 - 124), spanning the space between adjacent vertical members and connected to a respective side of the vertical members (101 - 105), the interconnection being fixed joints, wherein at least two vertical members (101 - 105) of the wall truss comprise hollow columns (301 - 309, 311-319); for at least two floors of the multi-story building: inserting a mating member (341 - 350) into the hollow columns (301 - 309, 311-319) of at least two of the vertical members for each wall truss (1, 2) and additional wall truss (3, 4), where the mating member (341 - 350) extends into both the hollow columns (301 - 309) of each wall truss (1, 2) and the hollow columns (311 - 319) of the additional wall truss (3, 4); affixing floor shelves, each including an upper horizontal element, on a top horizontal beam of a wall truss, wherein the floor shelf also includes a substantially planar surface extending in a horizontal direction perpendicular to the horizontal beam to which it is affixed into the interior of the multi-story building; and stacking additional wall trusses (3, 4) on top of the plurality of wall trusses (1, 2) installed for the floor below, by setting the bottom of the hollow columns of the vertical members (311 - 319) of a set of wall trusses (3, 4) on the vertical members (301 - 309) of the existing wall trusses (1, 2) of the floor below. inserting a mating member (341 - 350) into the hollow columns (301 - 309, 311-319) of at least two of the vertical members for each wall truss (1, 2) and additional wall truss (3, 4), where the mating member (341 - 350) extends into both the hollow columns (301 - 309) of each wall truss (1, 2) and the hollow columns (311 - 319) of the additional wall truss (3, 4); affixing floor shelves, each including an upper horizontal element, on a top horizontal beam of a wall truss, wherein the floor shelf also includes a substantially planar surface extending in a horizontal direction perpendicular to the horizontal beam to which it is affixed into the interior of the multi-story building; and stacking additional wall trusses (3, 4) on top of the plurality of wall trusses (1, 2) installed for the floor below, by setting the bottom of the hollow columns of the vertical members (311 - 319) of a set of wall trusses (3, 4) on the vertical members (301 - 309) of the existing wall trusses (1, 2) of the floor below.