Abstract: A construction system for constructing multistory buildings is disclosed. Concrete joists are poured in place, using high-strength concrete. The concrete is poured into a removable, reusable ganged-form structure. The sides of the joist forms swing away from the joists after the concrete is set. Monolithic slab soffits, comprising an underlayer of gypsum board and an overlayer of concrete are pre-cast and moved into place to connect the joists before pouring of the joist concrete. The combination of pre-cast soffits and poured-in-place joists permits rapid and inexpensive construction of the multiple floors of a building. Alternatively, the slab soffit may be poured in place, in the same pour as for the joists, by placing fire-resistant boards between adjacent joist forms, thereby eliminating the need for cleaning any form work in those areas.