Foundation Design – Raft Slab

Foundation Design – Raft Slab

Waffle SlabRaft slab foundations, or waffle slabs as they are sometimes called, were developed in the 1980s as a response to more traditional strip footing foundation failures in expansive clays. These have since been adopted in Christchurch following the earthquakes as they are much stiffer and less likely to fail during earthquakes.

In Warkworth, Ashby Consulting Engineering spent time developing the tools and expertise to design strong, cost effective stiffened raft slab foundations for domestic and commercial projects. This expertise has since been adapted to suite liquefaction prone soils in the Christchurch Area.

As they are specifically engineered for each structure it is not “one size fits all”. Accurate numerical loading calculations and rib placement are critical.

Ashby Consulting Engineering can provide the following Raft Slabs Designs which are suitable for most properties:

  • Standard Waffle Slab – typically suitable for TC1 sites and TC2 sites
  • Enhanced Waffle Slab – (TC3)
  • Piled Waffle Slab – might remove the need to strength then near surface material
  • Relevellable Waffle Slab – We are an approved designer for Firth’s Relevellable System

Typically Raft Slabs do not require excavation and are specifically designed for each building, they can be more robust, quicker to build and often less expensive than traditional foundations.

Contact Ashby Consulting Engineering re Raft Slab Foundations. Phone us now on 03 383 0514 or send us an email about your foundation requirements.