Technical Booklet C Site Preparation and Resistance to Contaminants and Moisture·Page 22·5.4(c)
Damp Proof Membrane positioning and sulfate protection
The DPM should be positioned above or below the concrete or insulation and continuous with damp proof courses in walls. If ground contains water soluble sulfates or risk of contamination, the membrane must be placed at the base of the concrete slab.
DPM above or below the concrete or insulation, and continuous with the damp proof courses in walls, piers and the like. If the ground could contain water soluble sulfates, or there is any risk that sulfate or other deleterious matter could contaminate the hardcore, the membrane should be placed at the base of the concrete slab (see BRE Special Digest SD 1 Concrete in aggressive ground: assessing the aggressive chemical environment: Part 1).
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