TPO - Single Ply Membranes
TPO (Thermoplastic Olefin/Polyolefin) Thermoplastic, PVC (Polyvinyl Chloride) roof membranes, commonly referred to as single-ply membranes, are flexible sheet materials that are used in one-ply or one-layer configurations. Constructed from ethylene propylene rubber, the thermoplastic roof membrane's chemical and physical characteristics allow it to repeatedly soften when heated and harden when cooled.
In addition, because of the chemical nature of thermoplastic membranes, the sheets are typically seamed by heat welding with hot air.
Properly installed TPO roof systems have service lives ranging from about 10 to 20 years, depending on the type of installation. When deciding whether a single ply membrane roofing system is right for you, it is important to first consider whether the building is suited for a single ply membrane at all.
Generally, single ply membrane roofing is appropriate when weight is a consideration, the roof has adequate slope, structural movement is expected, re-covering an existing membrane or installing in cold weather, among other factors. The two installation alternatives of TPO membranes are: fully-adhered and mechanically-attached.
Points to Consider For Installing A TPO Roofing System
- Fully-adhered means that the roof is "glued" to the substrate using a special adhesive where the glue creates a chemical bond with the membrane
- Mechanically-attached membranes are those that use some type of special screw-type fastener to secure it. The type of fastener will depend on the type of substrate but all fasteners are generally screw-type fasteners.
Advantages of TPO Roofing Systems
- Energy-efficient (when cleaned annually)
- TPO is often one of the most economical options for a large low slope roofing areas with no rooftop equipment to maintain (no foot traffic)
Limitations of TPO Roofing Systems
- (Due to it's single-ply nature) Is highly susceptible to foot traffic damage resulting in tears, impacts, cigarette burns, punctures, etc.
- Because TPO is fairly new roofing material. Developed in the early 1990’s many manufactures had their own unique formulations. This lead to great inconsistency in the performance of roof especially the weld points
- Because of faulty chemical formulas, many TPO roofs have failed and needed to be recalled. Reported problems included seams coming apart, leaks and membrane failures, especially when exposed to excessive heat over a prolonged period of time. The good news is that reputable manufacturers have taken care of these issues and ASTM standards have been critical in achieving a base line of minimal acceptable performance and features
- Bottom line; if you choose to purchase a TPO roofing membrane, you are getting a product that does not have a long track record of flawless performance, but instead has a long track record of revisions and improvements
- TPO roofing is not effective for flat roofs without slopes; they must have a slope to maintain proper drainage
- This is NOT a do it yourself project and professional installation is nearly mandatory. You do not want a “NEW” company or installer welding TPO
- Many of the problems associated with TPO were related to not looking into the TPO roofing details and spec’s required by the manufacturer