A structural two-way truss slab of egg-crate form is provided with manufactured pans that have openings in the sidewalls thereof with interconnecting members between the openings. The arrangement is such that the pan can remain in place and thus provide a finished ceiling effect. The system further provides an ability to run air-conditioning, electrical, plumbing and other conduits through the slab itself after the slab has been poured. The slab is structurally equivalent to conventional two-way slabs but is of less gross weight.