Soil Testing for Building Control and Warranty (NHBC) Requirements

Fast, reliable soil plasticity testing — helping you meet building control and NHBC standards

If you’ve been asked to provide Atterberg Limits or Plasticity Index (PI) test results for your site, you’re in the right place.


At Impact Geotechnical, we carry out laboratory testing to determine your soil’s plasticity index — providing clear, professional reports accepted by Building Control, NHBC, and other building warranty providers across the UK.

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Why Building Control and NHBC Require Plasticity Index Testing

When building on clay or mixed soils, foundations must be designed to prevent damage from shrink/swell movements caused by seasonal moisture changes.


Building Control officers and NHBC inspectors use Plasticity Index results to:

  • Classify the soil type (low, medium, or high shrinkage potential)
  • Determine minimum foundation depths
  • Assess the risk of heave or settlement
  • Confirm compliance with NHBC Chapter 4.2 (“Building near trees”) and related guidance



Without this data, your site investigation report or foundation design may be rejected or delayed.

Our Soil Shrinkage Potential Testing Service

Impact Geo provides a complete Atterberg Limits testing service, ideal for small developers, self-builders, and consultants who need quick, accurate results.


What’s included:

  • Testing carried out by experienced geotechnical technicians
  • Liquid Limit, Plastic Limit, and Plasticity Index calculations
  • Professional report with results summary and soil classification (in line with BS EN ISO 17892-12 / BS 1377-2)
  • Turnaround times typically 5-10 working days from sample receipt
  • Results suitable for Building Control, NHBC, and warranty providers


If required, we can also arrange soil sampling on site or guide you on how to collect and label samples correctly.

How to Book a Test

  1. Contact us with your site details and number of samples.
  2. Send or deliver your soil samples to our laboratory (we’ll provide instructions).
  3. We’ll carry out the tests and email you a certificate and report ready to send to your Building Control officer or NHBC representative.


Need your results fast? Express testing options are available on request.

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