Construction of a new office building for the American Concrete Institute presents some unusual and difficult problems for the contractor. Exposed concrete was expressed structurally in the cantilever folded plate roof; exterior decorative concrete included thin precast, exposed aggregate panels set in aluminum window frames and heavier grade-level precast grills; interior decorative concrete treatment included two types of continuous fluting on the structural bearing walls. The plan showed a reversed fold, folded plate roof cantilevered from each corridor wall. Deep X-shaped beams with diamond-shaped openings for skylights formed the tie across the corridor. The design was for cast-in-place construction but specifications permitted precasting at the contractor's option. Knowing that the architect set high standards for finish appearance, the general contractor, Pulte-Strang Co., Ferndale, Michigan, selected the precast option for the folded plate roof principally because precasting the sections upside down permitted achieving sharp, formed lines for the surfaces to be exposed. Roof units were erected as simple beams on falsework at the window line and the corridor bearing wall. Two steel shims 4 inches high on the bearing walls plus the point support on falsework gave a stable three-point bearing that permitted adjustment to match adjoining units. After completing main welds above the corridor and tie down welds to dowels in the bearing wall, a non-shrink grout was used to complete the center joint and bearing on the wall. Transverse roof joints above the welds were completed to sharp edges with a patching grout containing a polyvinyl acetate emulsion as an admixture and as a bonding coat. A camber of 1 and one-fourth inches was provided at the window line; immediate deflections averaged five-sixteenths of an inch. The windows are fixed by a sliding joint for live load and creep deflections. The exposed roof slabs are covered only by a sprayed vinyl treatment so that the architectural integrity of a concrete surface is retained.