An impervious membrane should always be applied as a Damp Proof Membrane (DPM) above or below a ground floor slab to stop ground moisture reaching the upper surface of the floor.
See Also
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DPM’s can be applied to either a suitable blinding layer under the slab or internally to the top of the slab. Consideration shouldbe given to applying the DPM to the top of the slab, as the installation and moisture sensitive internal finishes are then protected from any residual moisture in the concrete.
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Saturated bricks below the DPCFind a suitable waterproofing solution for this or any application below:
