Flat roofs are a common feature across New Zealand homes, commercial buildings, and industrial facilities. When it comes to waterproofing these surfaces, torch-on roofing has long been a trusted solution. But what exactly is torch-on roofing, how does it work, and is it the right choice for your property? This guide covers everything you need to know.
What Is Torch-On Roofing?
Torch-on roofing — also known as torch-applied membrane roofing — is a bitumen-based waterproofing system applied using an open-flame torch. The heat melts the underside of the membrane, bonding it directly to the roof substrate. The result is a seamless, watertight layer that resists water penetration, UV exposure, and the kind of temperature swings common across New Zealand's varied climate zones.
There are typically two layers in a torch-on system: a base layer and a cap layer. The cap layer is often finished with mineral granules that reflect UV rays and add durability.
Why Torch-On Roofing Suits NZ Conditions
New Zealand's climate presents unique challenges for roofing. From the humid, wet winters of Auckland and Northland to the freeze-thaw cycles of the South Island, roofing membranes need to be flexible, durable, and resistant to moisture.
Torch-on membranes are specifically engineered to handle these conditions:
- Flexibility in cold temperatures: Modified bitumen membranes remain pliable even in sub-zero conditions, reducing the risk of cracking.
Common Applications in New Zealand
Torch-on roofing is used across a wide range of building types in NZ:
- Residential flat roofs and low-pitch roofs on modern homes and extensions
The Installation Process
Proper installation is critical to the performance of a torch-on roof. Here's what a professional installation typically involves:
1. Substrate preparation: The existing roof surface is cleaned, repaired, and primed to ensure good adhesion. 2. Base layer application: The base membrane is torched down, creating the first waterproofing layer. 3. Cap layer application: The cap sheet is applied over the base, overlapping seams to eliminate weak points. 4. Detailing: Flashings, penetrations, and edges are carefully sealed to prevent water ingress at vulnerable points.
This is not a DIY job. Torch-on roofing requires specialist equipment and training. Improper application — particularly around seams and flashings — is the leading cause of premature failure.
Signs Your Torch-On Roof Needs Attention
Even the best torch-on roofs require periodic inspection and maintenance. Watch for these warning signs:
- Blistering or bubbling on the membrane surface, which can indicate trapped moisture
Catching these issues early can prevent costly structural damage and extend the life of your roof.
Torch-On vs. Other Flat Roof Systems
New Zealand building owners often compare torch-on roofing with alternatives like TPO (thermoplastic polyolefin) membranes and butynol (EPDM). Each has its place:
- Torch-on is ideal for large commercial areas and where a proven, long-lasting system is required.
The right choice depends on your building type, budget, and long-term maintenance plans. A qualified roofing specialist can assess your specific situation.
Maintenance Tips for NZ Building Owners
To maximise the lifespan of your torch-on roof:
- Inspect twice a year — ideally before and after winter — and after any major storm.
Get Expert Advice from Membrane Roofing Applicators
If you're considering torch-on roofing for a new build or replacement, or if your existing flat roof is showing signs of wear, the team at Membrane Roofing Applicators is here to help. We specialise in flat roof waterproofing systems across New Zealand, including torch-on, TPO, and butynol membranes.
Contact us today for a free assessment and quote. Our experienced applicators will recommend the right solution for your building and ensure it's installed to the highest standard.