Pyrite contamination

Applicable sections of the Technical Manual

Section 1 - Ground Conditions

Appendix C.1 – Materials, Products, and Building Systems

Performance requirements

The designer shall ensure the suitability of the ground conditions for the purpose of supporting the development, by carrying out necessary site investigations including chemical analysis of soils to ensure that there are no harmful contaminants or hazards, which could cause deterioration of any element of the development.

Further information can be found within the ‘Ground Conditions’ section of our Technical Manual.

Guidance

Where backfill is specified it should be certified by a competent laboratory that they are of a suitable nature and quality in relation to the purpose and conditions of their use. They should be chemically analysed to check if such materials contain any chemicals, which should also include the petrographic indicator of swelling potential.

The Petrographic Swelling Potential Indicator (PSPI) varies from 0 to 100 but is not a percentage. It is intended to be a visual evaluation of the sulphatic swelling potential of the materials used.

The following figures present the petrographic swelling potential that may generally be associated with the different PSPI values:

• 0  – 10  Negligible
• 11 – 20  Low
• 21 – 40  Low to medium
• 41 – 60  Medium to high
• 61 – 80  High
• 81 – 100 Very high

Any materials with a PSPI in excess of 20 will not be acceptable for warranty purposes.

Additional References

Building Regulations: 

• Regulation 7: Materials and Workmanship.
• Approved Document C

Technical Manual:  

• Ground Conditions

BRE Digest DG 522:  

• Hard-core for supporting ground floors of buildings:
• Part 1: Selecting and specifying materials
• Part 2: Placing hard-core and the legacy of problem materials. (Replaces BRE Digest 276 which has been withdrawn.)