Ribraft foundations, Christchurch.

When a slab job goes wrong, it is rarely a concrete problem. It is a coordination problem: a slab poured before the plumber finished, penetrations in the wrong place, no set-downs where the tiler needed them, levels the framing crew spent their first day packing out.

The other Christchurch classic is the wrong system for the ground: a standard raft on land that needed engineering, because nobody checked the TC class before quoting cheap. That one does not show up until it is the most expensive problem the house has.

A ribraft floats the house on an engineered concrete raft instead of digging strip footings into ground you cannot trust. Polystyrene pods grid out the floor, steel mesh and reinforced ribs run between them, and the whole thing pours as one slab: stiff, light on the ground, and fast.

That is why it took over Christchurch after the ground moved: a raft spreads load across the whole footprint, so it rides ground movement instead of cracking along it. On good TC1 gravel it is simply the quickest, cleanest way to a finished floor. On harder ground it is the starting point the engineered systems build from.

We pour these week in, week out. Boxing day one, pods day two, mesh day three. Concrete docketed from the plant, screeded and finished the day it goes down, not rushed.