Why waterproofing fails

12 March 2023
By Chris Jakovljevic

On the east coast of Australia, we are – if you can believe the weather pundits – coming out of the latest La Nina event. Over two years we have seen torrential rain, devastating floods and buildings ruined. For the most part, the CBD regions have faired better than inland areas, however, at Remedial, we have seen unprecedented demand for waterproof inspection services for high-rise structures as more people have seen their existing waterproofing fail.

Flat roof structures are widely used in various buildings, including residential, commercial, and industrial, due to their functional (ability to put items such as air conditioning units on them) and aesthetic advantages. However, flat roofs are more prone to water infiltration and damage than pitched rooftops due to the fact they do not drain as quickly as an angled roof. Therefore, it is essential to apply appropriate waterproofing systems to prevent water penetration and protect the building from moisture-related problems such as mold, decay, and structural damage. Whilst concrete is solid and strong, it has been proven time and time again to be a poor insulator from water. Instead, bitumen-based, rubber, and cementitious waterproof membranes are some of the most common waterproofing materials used on flat roofs.

Here is the catch though, over time, these materials can degrade and lose their effectiveness, which can lead to costly and disruptive repair or replacement projects.

Why does Bitumen Waterproofing fail?

Bitumen-based membranes are made of a blend of asphalt, polymers, and solvents, and they are applied in layers on the roof surface. The upper layer of the membrane is typically covered with a mineral or aluminum finish to protect it from the sun’s harmful UV rays. However, over time, this protective layer can wear off, exposing the underlying bitumen to UV radiation. This exposure can cause the bitumen to dry out, crack, and lose its flexibility, leading to water infiltration through the minute, yet numerous cracks that now exist.

Another factor that can contribute to bitumen-based waterproofing degradation is thermal expansion and contraction. Being as exposed to the sun as they are, there can be wide fluctuation in temperature between day and night, with seasonal fluctuations causing even higher swings. High temperatures cause the roofing material to expand and contract, and with sudden wild rain (such as our summer storms) rapid cooling, which leads to cracks and gaps in the membrane. This can allow water to penetrate the roof structure and cause damage.

Why does Rubber Waterproofing fail?

Rubber roofing is another popular option for flat roofs, but it can also degrade over time due to UV exposure and temperature fluctuations. Rubber roofing is made of ethylene propylene diene monomer (EPDM), a synthetic rubber that is highly resistant to heat, cold, and moisture. However, EPDM can become brittle and shrink over time due to exposure to UV radiation, causing cracks and gaps to form in the roofing material. Additionally, EPDM can also be damaged by chemicals and pollutants in the environment, which can break down the material and compromise its waterproofing properties. Another issue comes from mechanical damage. Over time, tradespeople drop tools, screw into the membrane or cut it (whether accidentally or by design to attach something) meaning that the integrity of the surface is compromised.

Once there is an area for water to seep in, it will, causing large water bubbles under the surface, finding cracks and causing ongoing structural damage to the building.


Why does Cementitous Waterproofing fail?

Cementitious waterproofing was often used in large industrial and commercial buildings due to its durability and resistance to water penetration. However, even concrete can degrade over time, particularly if it is not properly maintained. One of the most common causes of concrete degradation is freeze-thaw cycling, which occurs when water seeps into the concrete and freezes during cold weather. The frozen water expands, causing the concrete to crack and spall. This can lead to water infiltration and structural damage, particularly in large concrete slabs such as flat roofs. Whilst this type of waterproofing is no longer employed, older buildings are susceptible still.

Damage caused by waterproofing failure

The reasons for waterproofing degradation can be complicated and various, but the impacts are all similar. Water infiltration can cause a range of problems, from cosmetic issues such as staining and discoloration to more serious structural damage such as rot and decay, concrete cancer and electrical issues. Additionally, water infiltration can create an environment conducive to mold and mildew growth, which can compromise indoor air quality and pose health risks to building occupants. And something not many people will tell you, but water ingress may also cause insulation to become wet, reducing its effectiveness and leading to higher energy bills.

What you can do

If you have noticed that you have even small areas where water is dripping, or where it is ponding on the flat roof surface, acting sooner than later could save you months of remedial rectification work, and huge repair bills.  Waterproofing is an essential component of flat roof structures, and there are various materials available to provide effective protection against water infiltration.  In other words, ongoing maintenance and inspection will help identify potential issues early and prevent costly and disruptive repair or replacement projects.

Over time, even the most durable materials can degrade and lose their effectiveness due to exposure to environmental factors such as UV radiation, temperature fluctuations, and chemicals.  If you have concerns about your building and where water is getting in, give us a call, we have a team of experts ready to help identify the issue and then provide advice on the best way to remedy it for you.