Substructure and ground-bearing floors

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Substructure and walls below DPC level shall use mortar which is suitable for the location and intended use. Issues to be taken into account include:

  1. mortar mix
  2. sulfate resistance.

Mortar mix

Mortar should comply with the design and should take account of the strength, type and location of the masonry. The selection of mortar for use below the DPC should follow the recommendations given in BS EN 1996-1-1.

The use of proprietary mortars and admixtures should:

  • account for the type of masonry unit and its location
  • only be used in accordance with the manufacturer’s recommendations.

For non-clay bricks or blocks, mortar should be used in accordance with the brick manufacturer’s recommendations.

Sulfate resistance

Sulfate-resisting cement should be used where:

  • sulfates are present in the ground, ground water or masonry
  • recommended by the brick manufacturer.

In such cases, sulfate-resisting cement to BS EN 197-1 should be used.