According to the structural form stress characteristics, stair forms can be divided into plate type, beam type, cantilever (scissor) type spiral type. The first two belong to plane stress system, the last two belong to space stress system.

The plate stairs are composed of stair section plate, platform plate platform beam. The step board is an inclined board with steps, which is supported on the upper lower platform beams, the lower end of the bottom layer is supported on the ridge wall. The advantage of the slab stairs is that the lower surface of the slab is flat the formwork is simple; the disadvantage is that when the span of the slab is large, the thickness of the inclined slab is large the amount of structural materials is large. Therefore, the slab stairs are suitable for the case of small variable load the span of slab is generally more than 3m.