At Zondo Roofing, we specialize in commercial roofing systems that are built to last. One of the most popular materials we work with is TPO (Thermoplastic Polyolefin) — and for good reason. TPO roofing is energy-efficient, durable, and cost-effective. But like any roofing system, its performance depends heavily on proper installation. One of the most critical steps in the process is heat welding the seams.

When done right, heat welding creates a waterproof, long-lasting bond that will protect your building for years. When done wrong, you’re looking at leaks, premature failure, and costly repairs. In this post, we’re walking you through the proper way to weld TPO on a commercial roof, based on years of hands-on experience in the field.

Step 1: Surface Preparation Is Key

Before you even power up a heat welder, make sure the surface is clean and dry. Dirt, dust, moisture, or debris can compromise the weld. We always:

• Sweep the membrane thoroughly
• Wipe seams down with a clean rag
• Use a cleaner or primer if needed (especially in humid or dusty conditions)

Even new TPO sheets can have residue from the factory, so don’t assume it’s clean just because it’s fresh out of the wrapper.

Protecting Your Home and Your Investment

Your roof is your home’s first line of defense against the elements. Homeowners must be proactive in cities like McAllen, Pharr, Mission, Edinburg, Mercedes, Weslaco, La Feria, Brownsville, and Harlingen, where tropical storms are frequent. Storm-damaged roofs affect home resale value, insurance coverage, and even health, especially if mold grows due to trapped moisture.

At Zondo Roofing, we understand residents’ unique weather challenges in South Texas. That’s why we provide fast, reliable roof replacement and repair services using high-quality materials designed to withstand Rio Grande Valley weather conditions.

Step 2: Test Your Welder Temperature

Heat welding isn’t a “set-it-and-forget-it” process. Ambient temperature, wind, and sunlight all affect how your equipment performs.

At Zondo Roofing, we always start by doing test welds on scrap TPO. This lets us dial in:

• Temperature (typically between 900°F–1100°F)
• Pressure
• Speed (depending on hand welder or automatic machine)

We test each morning and whenever weather conditions shift. A good weld will show a solid, consistent bond — no voids or skips. The seam should tear internally before the weld gives out.

Step 3: Overlap and Alignment

The TPO sheets need to overlap at least 1.5 inches to 2 inches at the seams. For machine welding, we often mark a chalk line to keep things straight.

Proper alignment ensures:

• The hot air gets where it needs to go
• The pressure roller doesn’t roll off-center
• A consistent seal is formed across the entire seam

Step 4: Heat Welding the Seams

Depending on the project, we use a robotic welder (for long straight runs) or a hand welder with a roller (for corners, penetrations, or small areas).

With a robotic welder:

• Feed the membrane into the nozzle evenly
• Walk alongside to monitor the weld
• Watch for wrinkles, smoke, or uneven speed

With a hand welder:

• Insert the nozzle between the two TPO layers
• Move the nozzle steadily while applying pressure with a silicone roller
• Maintain consistent speed — too fast, and the weld won’t bond; too slow, and you risk burning the membrane

The goal is a glossy, tight seam with no gaps, air bubbles, or cold spots.

Step 5: Seam Inspection and Probe Testing

After welding, allow the seam to cool for a few minutes. Then we use a seam probe — a rounded metal tool — to check every inch. We’re feeling for:

• Gaps or voids
• Incomplete welds
• Areas where the probe slips between the layers (a sure sign of a missed weld)

Any issues are marked and repaired immediately using the hand welder and roller.