Have you ever seen contractors on a building’s roof using flames while laying materials on the internal structure? If so, you might have just been witnessing torch-on waterproofing works. For the vast majority of us, the term “torch-on waterproofing” would be foreign.

Torch-on waterproofing is a technique used by waterproofing contractors to waterproof both commercial and domestic properties’ exteriors. Known for its effectiveness and durability, it is strictly a professional technique. Most suppliers of components of this approach will only sell required materials to professional waterproofing specialists.

In this article, we will walk you through everything you need to know about torch-on waterproofing.

Introducing Torch-On Waterproofing

The term “Torch-on” is derived from the way roofers apply it. It is one of the most used waterproofing techniques that involve using a blowtorch to melt modified asphalt along with viscous organic liquids onto the area.

Predominately used for flat and slightly angled roofs, it is an excellent waterproofing solution that could last for over 20 years depending on the numbers of layers used. Other common uses of torch-on waterproofing include that of decks, balconies and planter boxes. This is a testament to its versatility and applicability.

Technique and Material Used

Torch-on roofing involves the usage of the specially modified asphalt — bitumen. Essentially, bitumen is a hydrocarbon that is derived from crude oil. A less spoken benefit of using bitumen is that it is non-harmful to the environment while remaining highly resistant to water.

The combination of synthetic rubberized polymers and asphalt creates a perfect waterproofing material that is flexible while resisting brittleness. With proven waterproofing capabilities, this method also has special insulation characteristics that will help maintain a more stable indoor temperature.

Typically, this technique begins with a layer of fiberglass felt as a base sheet for the roofing material to be torched on. Next, the bitumen layer is rolled out. A torch is involved to melt the asphalt, effectively sealing the layers via heat.

Depending on needs, the last step would be to lay more layers or different type of layers depending on needs.

Types of Torch-On Membranes

There are two main types of torch-on membranes that contractors use – APP & SBS. It should be noted that contractors avoid ever combining or cross over these two types of torch-on membranes.

Atactic Polypropylene Plastic (APP)

Atactic Polypropylene Plastic modified asphalt is the most commonly used type of torch-on membrane. Most notably, it melts well when heated with a torch and thus gives contractors the flexibility and ease required for their projects.

Styrene Butadiene Styrene (SBS)

Styrene Butadiene Styrene, as a rubber modified asphalt, in contrast does not torch well. As such, it is mainly used in wall flashings or regions that require a highly flexible sheet.

Advantages of the technique

High Reliability

This is a proven technique that is usable for a lot of different scenario. The torch-on process creates a surface that is perfectly waterproof. On top of that, it is puncture-resistant which means you won’t need to worry about any sudden roof leakage.


As one of the most durable materials in the market, it is able to last more than ten years depending on the number of layers used. Furthermore, torch on systems help to reflect harmful sun rays while also being non-water soluble, non-biodegradable and non-carcinogenic.

Safe to Use & Environmentally Friendly

Any fumes released during the torch-on application are not harmful to our respiratory systems and have relatively low carbon footprint.

Does not Require the Removal of Existing Roof

Different from most waterproof techniques, the torch-on roofing can be applied on current roofs. This allows for a speedy process and the special needs of unique cases. However, it is most recommended to remove your existing roof so that the torch-on roofing will last longer.

Suitable for Other Application Areas

Torch-on waterproofing is a suitable technique for full water immersion and sub-soil applications. This makes it an ideal choice for sealing areas like balconies, roofs, decks, box gutters and planter boxes.

Disadvantages of the Technique

Professional Installation Required

Due to the special set of expertise required, torch-on roofing requires waterproofing specialist to carry out the installation. This is because it is a tedious process involving multiple layers and a blowtorch. Whenever fire is involved, it is always best to leave it to professional as they are trained to manage fire hazard risks.

Slightly Costly

Due to the extensive process to apply torch-on waterproofing roofs, it is expected to be steeper in cost. However, the offset is that torch-on roofing last for a really long time (>10 years) and is extremely durable. Ultimately, it is a cost-effective long-term solution that only requires a little bit more of initial investment.

Starting the Torch-On Waterproofing Process

Now that you have learned all that you need to know for the torch-on waterproofing process, you are already better equipped to make an informed decision for your waterproofing needs. The first thing you should always do is to engage a waterproofing contractor in Singapore for a free consultation and quotation.

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