Structure / Concrete / Slabs and Footings / Waffle Raft

1 min read 26 November 2023

Engineers apply clever science and can use concrete efficiently on poor quality soils.

These slabs are very stiff and use low cost polystyrene blocks to create deep ribs throughout. However, with anything difference we need to learn new stuff including:

  • careful placement of reo in the ribs achieves compliant concrete cover
  • coordinate all services especially sewer drainage. I like to minimise pipes under slabs on reactive clays. And if there are any, they must be able to move with any extreme soil movement. TIP Install a flexible joint (repair socket) under outside of slab.
  • vibrate the ribs carefully too. Don’t be lazy!
  • the face of perimeter beam is part of the termite barrier – make sure this is also carefully vibrated and minimum Class 2 finish
  • joints in larger slabs exactly as specified to accommodate the intense stresses going on under the slab.


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