Slab depth is typically 75 mm (3 in) to 130 mm (5 in) thick.[5][2] As a rule of thumb, the depth should be ​1⁄24 of the span.[5] The width of the ribs is typically 130 mm (5 in) to 150 mm (6 in), and ribs usually have steel rod reinforcements.[5] The distance between ribs is typically 915 mm (3 ft).[3] The height of the ribs and beams should be ​1⁄25 of the span between columns.[3] The width of the solid area around the column should be ​1⁄8 of the span between columns.