houses, Renovations

Waterproofing a Roof

Warren Heath

A leaking roof can really take the joy out of cuddling up inside on a cold, drizzly day. Similarly, mould due to moisture is just plain unsightly. The good news is that such problems are entirely avoidable if you invest in a good protective system that will keep the elements at bay. We asked Sonia Nogueira, Operations Manager of Coprox International for a few tips on how best to waterproof your roof:

Step 1:

  • Apply a new screed over the existing roof using Coprox Waterproof Cement Additive in the mix according to the following instructions: 1) Add 2.5kg of the Waterproof Cement Additive to every 50kg of cement used. 2) Mix dry ingredients thoroughly. 3) Add required quantity of water to the dry mixture using recognized building mix ratios. 4) Mix wet ingredients thoroughly before use.
  • Allow the screed to dry and cure for a minimum of 21 - 28 days before proceeding with the next step.

Step 2:

  • A two-coat brush-on application using Cobond as a Seamless Waterproofing Membrane system should be applied onto the surface of the screed. Mix the application according to the following instructions: 1) Decant 5 litres of Coprox Cobond into a clean plastic container and stir thoroughly. 2) Slowly sprinkle 5kg of the desired colour Coprox Masonry Waterproofing into the container. 3) Mix, preferably using a mechanical device, until smooth and free of lumps. 4) Stir the solution frequently throughout the application.

First Coat

  • Use the Cobond solution immediately following mixing. However, delay application if rain is imminent, during high winds or freezing temperatures.
  • Make sure that the screed has properly cured and is free of moisture. Remove any dust, dirt or foreign matter.
  • Apply the first coat using a suitable brush. Brush strokes should be applied in one direction to a thickness not exceeding 1.5mm.
  • Thoroughly cover depressions, fine cracks and pinholes.
  • Ensure that, when bridging joints or abutments of slabs and walls, the application covers the joint by at least 75mm on either side.
Second Coat
  • Ideally, the second coat should be applied after approximately 30 minutes, as soon as the first coat is dry to the touch.
  • If the second coat can only be applied later, ensure that the first is free of moisture prior to commencing application.
  • Apply the second coat  at right angles to the first coat, again to a thickness of 1.5mm.
  • Keep the application protected from rain and allow it to dry for at least 48 hours.
For more advice on waterproofing visit the Coprox International website, drop them a mail at or call them on 011-579-4300.