Waffle pod slab
A waffle pod slab uses polystyrene void formers to create a concrete rib grid, preferred on highly reactive (H1/H2) clay sites in Australian residential construction.
Ask Chalkline about this →A waffle pod slab is a type of slab on ground that uses polystyrene void formers (pods) placed on the prepared subgrade to create a grid of concrete ribs. Rather than bearing directly on the soil, the slab sits on the rib grid with the pods leaving a void beneath the flat panel. This void allows reactive soil to move without lifting the slab.
Waffle pod slabs are the preferred system on highly reactive sites (Class H1 and H2 under AS 2870:2011) and are increasingly common in Victoria and Queensland. The rib grid provides greater bending stiffness than a conventional stiffened raft for the same concrete volume, making them efficient on difficult sites. They require a full engineering design and are more costly to form up than a stiffened raft on a lower-reactivity site.
Also known as: Waffle slab, void form slab, rib and pod slab.
Category: Structural.
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Last updated: 2026-05-07. Verified: 2026-05-07. Quarterly review for currency.