Roof Waterproofing

Roofs are a critical point of a building which is subject to the elements. Expansion and contraction of exposed concrete can lead to cracks, water penetration and concrete cancer. Waterproofing your roof with a durable long lasting membrane will protect your building from costly premature degradation.

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Torch-on Membranes

Where possible we prefer to use bitumen torch-on membranes. These membranes are a 2 layer system that consist of;

  • Substrate preparation.
  • Priming the roof area.
  • Applying a 3mm base sheet.
  • Applying a 4mm UV stable cap sheet.
  • Dressing with flashing and UV stable granules.

Torch-on membranes have been around for many years and are a reliable long lasting roofing membrane.
The product warranty for bitumen torch-on membrane is 20 years.

Bitumen torch-on membranes are applied using an LPG gas blowtorch to heat both the substrate and waterproofing membrane causing a molten bitumen to form. Once the molten bitumen is formed the membrane is then rolled onto the substrate to penetrate into the concrete surface and cool leaving a very strong waterproof bond.

Polyurethane roof waterproofing

Polyurethane is a simpler process to apply but can be a little more technical in regards to preparation, priming and weather conditions.

The main factor that can influence the quality of a polyurethane waterproofing membrane on a roof are;

  • High Wind
  • High temperatures
  • Forecast rain

We tend to only apply polyurethane membranes on a roof if the conditions are perfect to do so or if the area has a lot of machinery or sensitive materials that do not allow for torch-on or PVC Sheet membrane.

The usual warranty period for a UV stable polyurethane waterproofing membrane is 10 years although when applied with a fleece layer impregnated within the polyurethane the warranty can be extended to 15 years.

Some polyurethane products state that they are self priming and a primer is not needed on the substrate before application. While this can work we always use a 2 part EPOXY primer to seal the substrate before applying the membrane.

The reason for this is there are unknown factors such as residual moisture that can be trapped within the substrate,  chemicals and oils that could also be present in the substrate. If the polyurethane is applied to a substrate and there are contaminants then the membrane can fail prematurely (i.e instead of 10 years we have seen roofs fail after just 3-4 years).

Once a membrane begins to fail by cracking or peeling then water is able to enter the substrate and soak the substrate up to 30cm from the entry point. Once the water has seeped under the membrane due to capillary action it causes a situation where heat from the sun can cause the moisture to evaporate and detach the membrane outwards from the original failure point causing the full failure of the waterproofing membrane.

We do apply polyurethane membranes when necessary but we prefer to use factory manufactured sheet membranes such as PVC heat welded membranes which can carry a product warranty up to 20 years or the bitumen torch-on membranes which also carry a product warranty up to 20 years depending on the system chosen.

PVC Sheet Membrane

PVC Sheet waterproofing membrane is a highly durable membrane that can be used in harsh demanding situations.

PVC sheet waterproofing membranes come in the form of a factory manufactured roll and are adhered together using a heat gun to weld the sheets together creating a seamless bond.

Some PVC sheet membranes are also rated to withstand chemical spills and situations where a membrane is needed in industrial situations and locations where spillage may occur from air-conditioning units, swimming pools and commercial kitchens.

PVC sheet membranes can also be used in bathroom situations where there is no room for failure. For example, bathrooms in shopping centres.

If you are looking for the most durable long lasting membrane then PVC sheet membrane may be something to consider.