Pros and cons: torch-on vs single ply membranes

Flat roof installation with propane blowtorch

At Danrae Group, we have decades of waterproofing experience. Our exceptional in-house team provides comprehensive services, including leak detection, solution design, remediation and preventative maintenance.

We know that delivering expert waterproofing solutions requires a thorough understanding of materials, brands and best applications. It means knowing the most suitable membrane type for diverse properties and environmental conditions.

Torch-on bitumen and single ply, for instance, are two membranes we frequently use – and each has properties that make it the ideal choice for certain projects. Here’s our guide to torch-on and single ply… including pros, cons and potential uses.

Man using torch

About torch-on bitumen

Torch-on is a dual-layer flexible sheet system composed of bitumen and selected polymers. The two primary types are Styrene Butadiene Styrene (SBS), a rubber modified asphalt, and Atactic Polypropylene Plastic (APP), a plastic modified asphalt.

Torch on membranes have a number of benefits, including UV-reflective properties, high tensile and tear strength, root resistance and puncture and fatigue resistance. They’re robust, durable and impervious to vapour pressure. As they are also non-water soluble, they can be a very good option for damp areas such as basements, lift pits or swimming pools.

Torch-on is a heat-applied membrane system. During installation, we move a blow torch over the entire membrane to bond the material to the surface and seamlessly blend edges. We may or may not use a primer, depending on installation location, and we do generally add a layer of polymer to enhance structural integrity.

Residential building under construction

Understanding single ply

The term single ply can describe a number of single layer waterproofing membranes, including EPDM, PVC and TPO. We install single ply membranes, reinforce with polyester and seal at the seams to form a continuous waterproofing layer across an entire site.

Every single ply membrane has unique traits that determine its suitability for particular spaces and environments.

They include CPE and EPDM (both flexible and bitumen compatible), FPO (suitable for use with aged bitumen; recyclable), PVC (compatible with PVC downpipes and fittings, can be laid over damp substrates), TPE (high UV/Ozone resistance) and VET (bitumen compatible).

In general, single ply membranes are lightweight, flexible, UV resistant, fire and chemical resistant and suitable for extreme climates. They have a lifespan of between 30 and 50 years.

Man fixing a cracked wall

Pros, cons and potential uses

Torch-on flexible roof systems are tested and proven for long-term durability, UV stability – and given they have two layers – extra security at edges and laps. Installation is not recommended over wet substrates and torch-on bitumen is not compatible with PVC fittings.

Torch on membranes can be sensitive to heat so may not be our first choice for extremely hot climates, but we may use them for areas such as planter boxes and flat roofs.

Given single ply membranes are environmentally friendly and aesthetically pleasing, they are quite popular for new constructions and public spaces, including strata rooftops. We may also use single ply membranes for sloping roofs and internal areas.

Danrae Group truck

Expert and advice installation

There is no one-size-fits-all waterproofing membrane. The Danrae team always recommends membranes after we’ve met with our customers, inspected the site and considered a whole range of factors, including area usage, environment and budget.

Installation is definitely not DIY. With torch-on systems for instance, waterproofers require stringent training and skill. It’s expertise that is not widely available in Australia, but we have team members qualified and experienced in exceptional torch-on installation – and in every other type of membrane.

At Danrae Group, we’re committed to first-class waterproofing and tailored solutions. Contact us for quality waterproofing diagnostic, design and remediation. Read more articles about membrane waterproofing.

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