Ribbed and waffle slabs

Ribbed and waffle slabs provide a lighter and stiffer slab than an equivalent flat slab, reducing the extent of foundations. They provide a very good form of construction where slab vibration is an issue, such as laboratories and hospitals.

Ribbed slabs are made up of wide band beams running between columns with narrow ribs spanning the orthogonal direction. Normally the ribs and the beams are the same depth. A thin topping slab completes the system.

Waffle slabs tend to be deeper than the equivalent ribbed slab. Waffle slabs have a thin topping slab and narrow ribs spanning in both directions between column heads or band beams. The column heads or band beams are the same depth as the ribs.


  • Flexible
  • Relatively light, therefore less foundation costs and longer spans are economic
  • Speed of construction
  • Fairly slim floor depths
  • Robustness
  • Excellent vibration control
  • Thermal mass
  • Good for services integration
  • Durable finishes
  • Fire resistance

More information on ribbed and waffle slabs can be sourced from The Concrete Centre publication Concrete Framed Buildings.

CQ Summer 2019

CQ archive

View 'Return of the Rib' article in CQ summer 2019

Concrete Frames Explained