TPO Roofing: Advantages and Disadvantages for Commercial Flat Roofs

TPO Roofing for Commercial Roofs 

A Thermoplastic Polyolefin, or a TPO roofing system, installed on commercial flat roofs, consists of a laminated vinyl membrane that comes in 2 thickness options; .045 and .060 thousandths of an inch, which is only equivalent to the thickness of a quarter.

TPO Roofing Advantages:

• The seams are welded, rather than glued, so they are less prone to separation if adequately heated.

• Contractors are certified by the manufacturer to install the membrane, and the manufacturer honors the warranty.   

• TPO’s white surface reflects much of the ultraviolet light, keeping the structure below cooler.

TPO Roofing Disadvantages:

• The system is relatively new to the roofing industry; only about 15 years, with a long track record of revisions and improvements due to surface and seam failures.

• Repairs are part of maintenance due to shrinkage from prolonged exposure to harmful UV rays causing stress on seams and flashing.

• Contractors must calibrate the welding machine correctly; otherwise, seams may come loose during the first freeze/thaw cycle and lead to water infiltration.

• The manufacturer’s warranty is only for 15-20 years.

• After both the walk-behind and hand-held welding, a seam probe is needed to check the welds. If the welding did not take, it would require patching.

• *Different welders must be used on long seams and short seams.

*It has been our experience that TPO seams are not welded uniformly, which causes the seams to fail and the roof to leak. The walk-behind welder that welds lengthy seems, cannot weld the short seams around skylights, vents, drains, and a/c units. A hand-held heat gun welds these tight areas, and the transition from where the larger heat welder left off to where the handheld heat gun welds become an issue because the applied heat differs. A good read is GAF’s study on TPO.

TPO Roofing Membrane

TPO is a single ply vinyl membrane, as thick as a single quarter, and comes in wide rolls of between 8 and 16 feet. A glue down process adheres the membrane to a substrate. The seams are welded with a walk-behind welder and a hand-held heat gun. When seams are heat-welded, it is of the utmost importance that the heat is correctly calibrated throughout the day of installation; otherwise, cold, wind and humid weather conditions will affect the quality of the welded seams. When TPO roofing has been installed, a tool must be used to check the quality of the seams to ensure that the heat-weld has taken.

TPO Roofing – Surface Preparation

Before installing a TPO roofing system, the substrate must be free of dust, dirt, and debris to provide a smooth surface for the gluing process, however, installing a recovery board over an existing roof, can also provide a flat surface. Regardless of the type of surface preparation, the TPO roofing system is still a single ply membrane that will not last as long as a two-ply Modified Bitumen Torch Down Rubber Roof Membrane System.

Summary

Although TPO is a good roofing system, there are still many inconsistencies with the heat-welded seams. Seam separation is prominent in cold weather climates. Also, the thin laminated membrane is very susceptible to punctures due to foot traffic, which is not covered by the manufacturer’s warranty. A good read is GAF’s study on TPO.