A site classified as Technical Category 2 (TC2) means that minor to moderate land damage from liquefaction is possible in future significant earthquakes.

Liquefaction is the term used to describe the temporary loss of strength and stiffness (bearing capacity) which can occur in soils that are subjected to strong shaking during an earthquake. The foundation system needs to comply with the design rules developed for TC2 floor systems as summarised in the MBIE technical document.

A Firth Codemark Ribraft foundation cannot be used for sites that are classified as TC2. Firth has two Ribraft solutions for TC2 ground conditions and both require specific engineering design by a CPEng to meet the TC2 design rules. A Firth Ribraft foundation can be engineered to withstand the temporary loss of support and differential settlement during and after an earthquake event.

The TC2 Ribraft foundation will require supplementary reinforcing and or fibres in the concrete and is sometimes achieved with 300mm pods, with an overall thickness of 400mm.