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Concrete Slab Solution for Marginal or Expansive Ground Conditions

Groundscrew piling is a highly efficient way to mitigate poor ground conditions. Underslab Piling is used as a ground improvement method, combining a standard 'good ground' raft slab design with perimeter and/or point load piling. This removes the need to excavate poor ground and reinstate engineered fill, reducing cost and waste, and therefore speeding up the construction programme.

Key Features
  • Eliminates expensive cantilever slab design, or large quantities of concrete for deep edge thickening
  • Groundscrews extend beyond the influence of the shrink / swell zone for expansive ground and support the slab edge
  • Groundscrews can extend down through ground with poor bearing capacity, or non-engineered fill into dense, stable zones below
  • Can provide underslab bridging to allow construction over deep buried services like water pipes
  • Groundscrews can provide slab edge piling close to existing retaining walls removing the need for alteration or improvement work to existing retaining by allowing the load to be transferred below the zone of influence
  • Groundscrew underslab piling provides a low impact, zero waste solution to eliminate removal of sub optimal soils from site
NZ-Owned Business
NZ-Owned Business
Scope of Use

Underslab piling as a ground improvement method for all types of structures. These include residential housing and commercial buildings with pile design loads of up to 150kN.

CodeMark certification simply calls for individual pile design loads and positions to be identified by the project structural engineer or slab designer on the slab layout plan. See CodeMark Certificate CMSNZ70132 for full Conditions and Limitations of Use.

StopDigging! provide on site static pile testing to verify what size and length of pile is required to achieve the necessary design loads.  Testing is performed in accordance with the recommendations of the geotechnical report for minimum embedment depths.

This allows formal fixed price quotations after testing has been completed, and eliminates any potential for onsite variations during installation/construction.

Limitations on Use

This application is specified to suit the site and structural requirements so a geotechnical report is required to determine the limitations of the ground conditions.

NZS 3604 Corrosion Zone D suitable
Corrosion Exposure Zone D
NZS 3604 Earthquake Zone Very High suitable
Very High Earthquake Zone
NZS 3604 Wind Zone Extra High suitable
Extra High Wind Zone
NZS 3604 Wind Zone Specific Design suitable
Specific Design Wind Zone
Statement of Building Code Compliance

The StopDigging groundscrew system is certified with a CodeMark certificate and complies or contributes to (where used as part of a system) the following performance clauses of the New Zealand Building Code:

  • Clause B2 – DURABILITY Performance B2.3.1 
  • B1 Structure: B1.3.1, B1.3.2, B1.3.3 (b, f, g, h), B1.3.4 B2 Durability: B2.3.1 (a), B2.3.2 (a)
  • F2 Hazardous building materials: F2.3.1

See CodeMark Certificate CMNZ10132 for full information.

In-Service History

Screw piles are not a new concept, they were first used in the 1850s. StopDigging! (a Swedish company, started in the early 2000s) moved into the New Zealand market in 2017 and have completed thousands of projects throughout the country.

Other Performance Attributes

StopDigging! Groundscrews have a design life in excess of 100 years in this application.

The StopDigging groundscrew system is certified with a CodeMark certificate which is the highest form of product assurance available in New Zealand.

B1 Structure compliant
B2 Durability compliant
Technical/Design Manual


StopDigging! Design Guide


Design Pathway


CodeMark: StopDigging! Ground Screw Foundation System

CMNZ70132 (Version: Aug 2023)

Design Declaration: Groundscrew Foundation System


Flyer: Concrete Slab Foundations in Expansive Soils
Installation Details
Standard Pod-Raft System Detail

The StopDigging groundscrew foundation system is a CodeMark certified and highly sustainable pile system for multiple applications.

Product Enquiries

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