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  • Writer's pictureSi Shen

What structural engineers need to know about waterproofing membrane

Waterproofing has always been and probably will always be a thorny issue to deal with for underground concrete structures. Waterproofing membrane (i.e. ‘tanking’) is a popular way of waterproofing solution. The structural engineer designing concrete structure does not have to be an expert in waterproofing membrane, but needs to have some basic knowledge of the requirement on the concrete structure imposed by the waterproofing membrane. the membrane is a delicate thing and requires a lot of careful detailing and handling.

It should first be noted that water always outsmarts human – waterproofing is a complete system, and regardless how strong each part is, it always fails at the shortest plank. Water typically leaks at joints, seams, cracks, etc.

What waterproofing membrane does not like in general:

  • Complex geometry and details, such as bends and curves

  • Penetrations – these are hard to seal off

  • Aggressive chemicals – these compromises durability of the membrane

  • Joints – movement joints, construction joints, etc.

Waterproofing membrane requires the substrate, which usually takes the form of blinding, shotcrete, piles, diaphragm wall etc., to have the following properties:

  • Dry – free from running water and dampness. Water behind the membrane could cause blister to the membrane, creating weak spots for leakage.

  • Clean – free from debris and grease. Any sharp objects could puncture the membrane.

  • Level – straight-line surface, free from dips, holes, cracks, which must be grouted or sealed before installing membrane.

  • Smooth – surface finish must be smooth enough to avoid sharp edges

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