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To Weld or not to Weld?

Posted: 6/20/2022

Can pre-taped (pressure-sensitive) EPDM accessories be used to flash details on a TPO roofing system?

The short answer is “Yes.” Today’s primer technology makes it possible, and it is a great option in some circumstances. It is not, however, a universal solution.

The advantages of using pre-taped accessories are obvious. It is fast, easy and cost-effective; just clean, prime, peel and stick. The roofing system will still be warranty-eligible. And – to the relief of the roofing crew – there is no need to haul welders, generators and extension cords up to the rooftop.

Those benefits make pre-taped accessories ideally suited for repair jobs or for when returning to a jobsite to wrap up the project after other tradespeople finish their work. (A common example would be installing a new TPO roofing system, then going back a few weeks later to install a pipe boot around plumbing stacks that were just added.) In these scenarios, pre-taped accessories make sense; they get the job done effectively and with less hassle, and the crew can move on to the next project.

And when flashing some TPO details, such as scuppers, EPDM tape products are required to complete the detail.

But pre-taped accessories have their limitations, and contractors must be aware of them.

Strength and durability are why contractors sell, and building owners buy, heat-welded TPO systems. When two sheets of TPO membrane are welded together, they essentially become one. If pulled from both ends, the sheets will tear before the weld breaks. Pre-taped accessories seal tightly, but primer and tape simply cannot compete with welding. That is why the warranty is limited to 20 years when pressure-sensitive products are used.

Roofing contractors take pride in their work and want to leave a job knowing they provided the best solution to meet the building owner’s needs. Pre-taped accessories have a place in achieving that goal with TPO systems. They are a great choice for making repairs or when returning to a jobsite to flash final details after other tradespeople complete their work. As a front-line solution, however, heat welding will deliver a more durable roofing system … and a happier building owner.

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