Waterproof membrane is a fundamental requirement of construction. A building or structure is waterproofed with the use of membranes and coatings to protect the structural integrity. Yet every year, high numbers of households and commercial premises report damages and issues that can be related back to inadequate waterproofing and application.
Sometimes a waterproof membrane is omitted from the design completely, but this is not the leading cause behind waterproofing failure. Poor workmanship is the leading cause of waterproofing failures with 90% of all failures being due to negligent or inadequate workmanship. A waterproof membrane is required to protect a floor (particularly if there are rooms beneath) from liquid which could penetrate it and/or damage it. Therefore floor penetrations such as floor wastes and other fixtures need to be accommodated with extreme care so that the continuity of the waterproofing is not impaired and subsurface drainage (above the membrane) is provided. The application of waterproofing to specially designed drainage systems can drastically improve the integrity of the waterproof membrane into the drainage.
Builders and waterproof contractors are often guilty of not allowing sufficient time for the correct preparation before the application of the waterproofing membrane. This may include the correct installation of:
- drainage flanges
- linear strip drains
- waterstop angles
- perimeter flashings
- pressure strip flashings
- fillets and bond breakers at coves
- topping screeds for ground falls
- overflow devices
- slip joints over suspended sheet flooring systems
The second leading problem is the failure to prime the respective parts and surfaces before the application of the waterproofing membrane. Poor subsurface drainage and saturation of tiling or topping screeds can result in the failure of the waterproofing bond to substrates. Surface priming for CFC, concrete, mortar screeds and plywood substrates should always be carried out with the manufacturer’s specified primers. Surface priming will reduce porosity, dusting, air entrapment (pin holing) and high residual moisture in the substrate, which will cause blistering of the membrane after curing.
Another contributor to waterproofing failures is residual moisture in the substrate causing adhesive failure or de-bonding of the membrane. It is critical for both the builders and the waterproofing contractors to test the concrete for mortar screed substrate before the application of waterproofing and installing adequate drainage to drain the waterproof membrane.
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