By Dymon Brady

Q) What precautions do Heating and Cooling technicians need to take when working on a roof?

A) When we have completed a TPO membrane roof, we inspect it for voids in the seams and for punctures. We usually don’t find anything during these inspections (called probing) but it is a helpful assurance against a leak.

Often we get a call from a building owner four months to several years after the roof has been completed and they report a sudden leak in the roof. This is usually due to a puncture from someone on the roof. It does take a lot of pressure to make a hole in a roof, unless one is dealing with sharp tools or edges of panels from an HVAC unit or swamp cooler. Technician awareness when working on roof top units is simple and helps prevent leaks.

Small TPO Puncture

One example of a leak in a TPO membrane roof caused from a rooftop A/C unit installation occurred about two years ago. We installed a nice white, energy efficient TPO membrane roof on a condominium complex in Saint George in 2004. In 2008 I got a call from the management company reporting a leak in one of the units. Amid my suspicion, I took a trip down to investigate the problem. When I got there, I saw that a new A/C unit had been installed over this condo unit. I took some membrane cleaner and started wiping the membrane clean. It didn’t take long to find several holes in the membrane caused by fragments of hot solder from the installation process.

TPO Puncture

The best precaution against this is for the HVAC technician to place a 3’ x 3’ piece of OSB or plywood down under the welding area. This will prevent any extremely hot fragments of solder from coming in contact with the membrane.

Fortunately, the repair was simple. I just heat welded a new peice of TPO over the area and their problems were solved.

Quick TPO Repair

That is one beautiful characteristic about this product. It does not lose it’s weld ability like PVC and EP Sheets do. I was just on an extremely large food processing plant roof yesterday that was done about 15 years ago in an EP Sheet. A general contractor just put two new exhaust units on the roof. As we tried to weld new membrane flashing around these units, we found it had lost its weld ability. We have found a solution that I won’t go into now, but the fact is it couldn’t be welded in a quick time frame like a TPO membrane could.

It made me all the more comfortable installing roofs for our customers!

TPO Punctures

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