Why Does My New Waterproofed Flat Roof Have Bubbles?

January 18, 2021

Why Does My New Waterproofed Flat Roof Have Bubbles?

You might have recently had your home or apartment block’s flat roof updated with new waterproof sealants in Sydney. Summer is a good time to do it. A month later, you suddenly notice that bubbles are appearing. Before your heart sinks, take a deep breath as this is not necessarily a crisis on your hands.

Sometimes bubbles manifest due to small amounts of air, vapour or moisture that have been trapped.

  1. Vapour

With flat roofs, there are often parapets. To continue the waterproofing seamlessly, membranes are used on the upstands and perimeters of the roof as well as overlapping into gutters. A solvent-based adhesive is used for its application. It is required to dry the adhesive to a state of “tackyness/tack off”. As the solvent dryness is not measured in a science laboratory but with the eye and hands-on a building site, the tack off/dryness might not be scientifically perfect when the rubberised liquid adheres to substrate. This can cause a small amount of vapour, forming bubbles, but they will more than likely disappear over time.

  1. Air

Another cause is simply air or, to be precise, expanding trapped air. If the rubberised waterproofing is bonded onto a timber deck, then sun-heated air can expand into bubbles.

Boards, beam, and concrete ribs have lots of small air pockets. These will expand after a batch of hot sunny days and will contract if the evenings are cooler.

One option that has proven successful is to paint the finished waterproofing surface with a white or pale colour acrylic roof paint. This can assist in reducing the heating up variances from as little as 5 degrees up to 15 degrees—definitely something to consider.

  1. Moisture

If your waterproofing was put on too quickly after winter or after an unexpected light shower, then you might have trapped moisture boiling and letting off steam under the membrane. A deck or surface needs a good 7 to 14 days to dry out thoroughly before being sealed if you want to ensure no moisture is trapped.

If you do have trapped moisture, there is a good chance this will reduce over time. If you have water pipes running through the deck and they have a little leak, then the problem may persist.

If you need help understanding a challenge with your waterproof sealants in Sydney, contact us today  Waterproofing Direct is a family-owned business which has been going for 20 years. Our enthusiastic team has a high level of in-depth technical knowledge in waterproofing applications of residential and commercial buildings.



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