Raft, pile, pier and beam foundations

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4.4.4Hazardous ground

Raft, pile, pier and beam foundations shall take account of ground conditions and hazards. Where hazardous ground has been identified, notice shall be given to NHBC before work commences.

Where there is hazardous ground, the design of foundations must be carried out by an engineer in accordance with Technical Requirement R5.

Where hazardous ground has been identified, NHBC should be notified in writing at least eight weeks before work on site begins, in accordance with NHBC Rules.

Where toxic materials, or those likely to present a health hazard are found, all available information should be supplied to NHBC, together with proposals for remediation.

Sulfate and acids
Sulfates and other chemicals can cause expansion and disruption of concrete. High acidity, for example in peat, or permeable soil with acidic ground water can cause damage to concrete. Where sulfates or high acidity in ground or ground water are present, reference should be made to Chapter 3.1 ‘Concrete and its reinforcement’ for guidance concerning acceptable concrete mixes.

Where concrete is at risk from chemical attack from the ground, or where the ground water is highly mobile, the level of sulfate and other chemicals should be determined in terms of the ACEC class (aggressive chemical environment for concrete class), in accordance with BRE Special Digest 1.