Over the past 35 years, single-ply thermoplastic membranes—such as TPO and PVC—have grown in popularity as an effective alternative to asphalt-based commercial and industrial roofing systems. This shift is largely due to single-ply’s ease of installation, relatively low cost, durability, and its energy-cost saving potential.
However, a singly-ply roofing system is only as good as its seam welds. To consistently create durable, watertight seams that can withstand heavy weathering (i.e. wind, rain, snow, standing water and sun), you’ll need to invest in the right equipment.
Following is an overview on the type of equipment needed for quality single-ply roof seam welding.
1. Automatic Walk Welder
Automatic walk welders are designed to roll along straight seams while applying consistent heat and pressure. The result is a quality, reproducible weld. When purchasing, look for a welder with:
- Digital display that shows both set and actual temperatures, giving you more control over heat output. These displays should also alert you of any malfunctions, such as a faulty heating element.
- Drive motor powerful enough to handle slight roofing inclines.
- Silicon-based pressure roller to ensure even pressure is applied to a seam despite small surface inconsistencies.
- Guide bar that will allow you to steer the machine without having to bend over, limiting fatigue and increasing daily output.
- Option to add extra weight over the pressure roller for greater seam pressure.
- Forward driving is a new feature found only in the Seamrover DD. Unlike other automatic welders, roofers can walk forward along the path of the seam versus backwards, where the potential of tripping is greater.
2. Hot-Air Hand Tool
Hot-air hand tools enable you to weld seams in corners or confined areas, and on curbs or vertical surfaces. When purchasing a heat gun, look for:
- Lightweight and ergonomic design to reduce muscle strain while holding it in various positions, or for extended periods of time.
- Heat-protection tube to avoid accidental burns.
- Overlap, or slot, welding nozzle attachment—these are specifically designed for welding two pieces of overlapped material.
3. Hand Pressure Roller
When welding with a hot-air hand tool, you’ll need a hand pressure roller to evenly press the heated material together and form a strong bond. Make sure your roller is:
- Made of silicone to ensure consistent pressure is applied despite surface inconsistencies.
- Approximately three inches wide for greater surface area coverage.
4. Wire Brush
When welding plastic materials, it is likely that some of the plastic will stick to the welder’s nozzle. A build up of this plastic can restrict airflow and potentially damage the heating element or the tool itself. Use a stainless steel or brass wire brush to scrape away the melted-on plastic while it is still hot, to keep your equipment in peak operating condition.
Poor power supply can impact a hot-air welder’s heat output, which can lead to inconsistent seam welds. For this reason, when possible, avoid relying on the building’s power outlets, and instead utilize a power generator.
To determine the generator power capacity you need, consider the electrical requirements of the tools being used and how may of these tools are operated simultaneously. Make sure the generator you select is available with a dolly cart for easy maneuvering. If possible, also get a hoisting kit, to simplify lifting the generator to the roof.
6. Extension Cords
Invest in extension cords to avoid having to repeatedly interrupt work to relocate or change your power source. Roofing power cords should offer the current carrying capacity required by your welder—for example, a 240-Volt automatic walk welder needs a 50 Amp/ 250 volt cord. The cord should also be:
- 10 gauge 3 wire
- 100 feet or less in length
- Design and Installation Tips for Single-Ply Roofing Systems from Roofing Contractor Magazine