Continuing Professional Development: Waterproofing below-ground structures

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  1. I have installed the Sika waterproofing systems on a number of different jobs from retaining wall, subways and ground slabs for buildings. With careful preparation and installation from a competent approved, trained sub-contractor the risk of water egress is minimized therefore prolonging the whole life of the builds.

  2. It was interesting to see that the article stated, “An external membrane is the most effective barrier.” When indeed the most effective barrier to water penetration is to ensure that, the water or hydrostatic pressure has somewhere to dissipate.

    In the 1999 court case of Outwing vs Weatherald, where Phil Hewitt Associates were the expert witnesses, the presiding Judge stated,“that overlapping self-adhesive membranes could not be expected to achieve a total or absolute watertight bond capable of resisting penetration by water pressure”. Another of his comments was “it is not realistic or reasonable to expect a bonded sheet membrane to be applied without any defects at all”. In my opinion the designer should always take into account less than adequate workmanship and to rely on better is at best unwise. I would recommend that any basement designer should read this judgment carefully before putting pen to paper.

    I along with many others take the view that the best method of avoiding hydrostatic pressure is to create a ventilated void surrounding and below any structure, where the hydrostatic pressure can either drain naturally or be pumped away. It is by far the simplest method, giving many years of life without issue. It’s funny… but that is what many historical builders taught us and it seemed to work pretty well for them.

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