Uncut pods and narrow beams in Werribee waffle slabs
What a pre-pour inspection checks in a waffle slab, and why beam width matters on reactive clay.
In short: A waffle slab is a grid of beams formed between polystyrene pods. If a pod moves or is left whole, the grid changes.
How a waffle slab works
Pods sit on the ground and the concrete fills the gaps between them, forming a grid of beams. The width of those beams and the steel inside them are what the engineer designed for the movement expected on your lot.
Pods that should have been cut
Sometimes the engineering calls for pods to be cut back to make room for a wider beam or a load point. We have found pods left whole in Werribee slabs where the drawings showed them cut.
Beams squeezed under their minimum
When a pod shifts or something sits in the trench, an internal beam can end up narrower than the 110mm minimum. It looks like a small gap, but it is part of the slab's stiffness.
Steel, chairs and cover
Mesh and bars have to sit at the right height on chairs, with enough concrete around them to stop rust. Bars resting on the ground or touching a pipe will not perform as designed.
Fixed in hours, not years
Almost all of these items are corrected before the pour on the same day. After the pour, the slab you have is the slab you keep.
Written by our local inspection team from work carried out in Werribee. Licensed building practitioners, Building & Plumbing Commission registration CDB-U 53425.
