8 include hand rails 12 the base panels 2 can be mounted directly onto bedrock onto a concrete slab or onto footing panels 13 provided the interlocking ceiling panels 4 are mounted on the upper ends of the ground wall panels 3 providing cantilevered arms extending outwardly therefrom ceiling slab panels 14 are attached to the cantilever arm extending into the building while specialized exterior panels e g shade panels 16 and hand rail panels 17 are mounted on the cantilever arm extending outwardly from the side of the building 1 the interlocking roof panels 5 are mounted on the upper ends of the second floor wall panels 3 providing cantilevered arms extending outwardly and upwardly therefrom roof slab panels 18 are attached to the cantilever arm extending over the building 1 while specialized exterior panels e g shade panels 19 can be mounted on the cantilever arm extending away from the building 1 while only a two story building is illustrated any number of floors can be constructed with the building system according to the present invention typical wall panels 3 illustrated in fig3 and 4 include an upper end 22 a lower end 23 a front face 24 and a back face 25 the wall panels can be.