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The best way to waterproof your concrete roof or balcony (part 2)

Pre-formed sheet membranes are an excellent choice for waterproofing your roof and there are two versions available in the market. Atactic Polypropylene Plastic (APP) and Styrene Butadiene Styrene (SBS). They are likely foreign terms to you. If you’re not involved in the waterproofing industry, then you’re likely unaware of what torch on membrane waterproofing is. Basically, torch-on membrane waterproofing is a modern technique that involves a membrane, consisting of bitumen that is modified with asphalt, being heated and therefore activated to cover whatever shape, material and size area.

Particularly in concrete waterproofing, the torch on membrane method has a number of great features. The asphalts used to modify the bitumen are usually either APP or SBS. APP is a plastic modified asphalt, and SBS is a rubber modified asphalt.


As mentioned previously, APP is a plastic modified asphalt. It melts quickly when it is heated and flows quite quickly like liquid wax. Due to this, it is fairly easily installed and doesn’t take a lot of time to do so. It is, however, not as resilient to being stretched as SBS.


A rubber-modified asphalt, SBS doesn’t torch as well as APP, and it, therefore, takes longer to install. It is a lot more malleable though and is therefore ideal for tight areas that require flexibility, as well as for wall flashings. SBS membranes can resist a lot of stress, are more resilient to tears and punctures, and tend to last longer.

When deciding on the modified asphalt to use, it largely comes down to the nature of the job. Both APP and SBS have advantages and disadvantages, so the choice is purely dependant on the area that requires waterproofing.
Concrete roofs have been an integral part of modern architecture for decades. Although they are typically seen as rooftops for commercial buildings, with changes to styles and architecture for residential buildings, homes are now also being constructed using this roofing method, with concrete shingles also starting to become popular in residential home structures. Even though concrete has been chosen as a superior material for both housing and commercial structures, it doesn’t mean that it is not susceptible to damage from the elements.

Waterproofing is one way you can help avoid damage from occurring earlier than anticipated and will inevitably help your concrete roof to last a lot longer. Adding waterproofing to your roof is a great way to protect your building and is well worth the investment.

Take measures to prevent concrete cancer
Concrete cancer can be devastating, but what causes it? The term itself is a bit of a catch-all for a variety of problems associated with concrete embedded with steel.

During construction, concrete is reinforced with steel bars or, in some cases, mesh. As a metal, steel can corrode after exposure to elements, like water or air. Steel that is corroding is forced to expand. This expansion causes the surrounding concrete to crack and even break. Cracking exposes even more of the steel which leads to increased oxidation and further damage to the concrete.

The belief that steel rods won’t come in contact with water because they’re surrounded by concrete is simply wrong. It’s important to understand that concrete is porous, and can absorb water. Also, a failure to adequately waterproof can increase the likelihood of concrete cancer. That’s why it’s essential to take the proper precautions to prevent concrete cancer. In situations that demand remediation, there are also things you can do.

The phases of concrete cancer

According to the Australian Concrete Repair Association (ACRA), there are four stages of concrete cancer progression. In general terms, the cost to fix concrete cancers multiples by roughly five through each stage of cancer’s progression in the concrete.
Design, construction, and curing of concrete
Corrosion has initiated, but damage propagation hasn’t started.
Deterioration begins to propagate through the concrete.
Advanced propagation concrete cancer and significant damage.
By the fourth stage, a complete knockdown of the structure might be the only solution. So remember to act early and if you think your premises has concrete cancer.

Concrete cancer assessment

In circumstances where concrete cancer is potentially affecting your structure, it’s best to call a professional. The first step in preventing or repairing concrete cancer is to have the structure analysed by a specialist. From here, recommendations can be made for remediation of the structure and ongoing prevention. In most cases, if you act early enough, the structure won’t need to be knocked down.

Choosing the proper sealer for your concrete

All exposed concrete should be protected with a sealer. A failure to use the right sealer, or to properly apply the sealer, increases the risk of concrete cancer to your structure, leading to expensive maintenance, repairs and replacements down the track. Sealers protect from moisture and prevent the build-up of mold and fungus on the concrete.

How long should a sealer last?

A good concrete sealer will last around five years before a reapplication is required. Resealing should be completed as regularly scheduled maintenance works and prioritized to prevent damage.

How does the concrete sealer work?

When waterproofing concrete, a topical sealer is applied to the surface of the concrete. The sealer is impermeable (provided it is applied correctly) and forms a waterproof membrane around the concrete, preventing moisture from entering the concrete. Topical sealers can be made from acrylic, epoxy and polyurethane-based materials. Many are decorative in colour and style.

Are there permanent sealers?

Permanent sealers do exist, though they leave a matte finish and are not available in decorative colours. Permanent sealers work by filling all the tiny holes in the concrete. They are made from silicate, silanes or siliconate and are also referred to as penetrating concrete sealers.

Concrete flat roof construction and issues

It is now more common to see home designs that incorporate a flat roof in order to make it look both appealing and elegant in style. However, proper design of such a roof style is required in order to ensure rainwater is drained away from the roof as soon as possible. ‘Water-ponding’, or the stagnation of water due to rainfall on such roofs, is the leading cause of the deterioration of concrete materials in roofing.

Variations in both temperature and moisture levels can lead to differential thermal movement. Combined with the potential acids left by rain that has evaporated, this can lead to the serious deterioration of what should be a stable, concrete roof.

Protecting your rooftop

Concert rooftops are exposed to the elements 24/7, so it’s essential that they are properly designed and waterproofed to prevent leaks through the roof. Rooftop leaking can cause ongoing issues in the home. Beyond water damage to the interior, it can also affect electrical components, lighting, and insulation. Ideally, you want preventative measures in place from the get-go, but if you think your concrete rooftop could be leaking or letting moisture in, it’s better to take action sooner rather than later.

Waterproofing a concrete roof for safety and longevity

Whether it’s a concrete rooftop that you’re concerned about, or perhaps there are other construction materials you want to ensure are stable and waterproof for years to come, there’s no doubt that investing in superior waterproofing systems is the best way to protect your assets. Not only can you protect your roof from the extreme climates Singapore endures, you can also have the peace of mind that you are doing the best that you can to protect your building and constructions from unnecessary damage.

And remember, if you’re having any other water problems in the home it’s best to consult with a plumber before taking action.

Need to waterproof the concrete in your home? It’s time to talk to Le Fong
Water damage to concrete in your home can lead to expensive consequences down the line. Why delay, when a solution could be as easy as contacting the experts. With extensive experience in waterproofing commercial, industrial and residential builds, Le Fong is ready to help you. Contact us today.