A concrete building panel has a slab and a plurality of ribs and beams. A series of horizontal holes in the end ribs are spaced at a selected constant spacing such that adjacent panels may be fastened together through them. In one type of panel, the slab is separated from the ribs to provide an air gap. Connections between holes in two adjacent concrete wall panels are made by a hollow conduit having an abutment at either end to engage the concrete wall panels. Other connections between adjacent panels involve a stitch with legs which extend through holes in the beams. Other connections involve a space made by vertical channels of horizontally adjacent panels. A plate fitted into the space aligns the adjacent panels and may extend upwards to align upper panels. Load bearing horizontal holes through the ribs are reinforced with reinforcing bar in the concrete arranged in generally triangular shapes. The concrete panels are formed vertically in a gang form. Connections between a roof panel and another roof panel or a wall panel are described.