Comparing The Different Single-Ply Roofing Membranes
Commercial roofing managers and owners in the East Texas region are typically overwhelmed by the many options available for low-slope roofs. Single-ply roofing membranes have three main group types. All of them are fairly complex systems and some have complex names or abbreviations to cause even more confusion.
Group 1: Thermoset Membranes
The polymer materials in these single-ply roofing membranes chemically crosslink. This means that chemical adhesives applied at the seams cures or vulcanizes the membrane strips into one giant membrane. There are several players in this category, which is also defined as the synthetic rubber membrane group.
There are five common subcategories of thermoset roof membranes:
- Ethylene propylene diene terpolymer (EPDM)
- Chlorosulfonated polyethylene (CSPE)
- Epichlorohydrin (ECH)
- Neoprene (CR)
- Polyisobutylene (PIB)
The most common thermoset roof membrane is EPDM. This frontrunner of the pack will be our comparison product. Note EPDMs main characteristics:
- Sheet widths range from 7.5 feet to 50 feet wide.
- Sheets are typically 45 millimeters and 60 millimeters thick.
- Seams are sealed using liquid adhesives or special formulated tape.
- The membranes commonly are black, but white is available.
Group 2: Thermoplastic Membranes
This family of single-ply roofing membranes are like the thermosets, but there’s no chemical cross-linking or vulcanization. The membrane strips are heat or chemical welded to create a single ply. Proper welds are as strong as the material. There are four common subcategories of thermoplastic roof membranes.
- Thermoplastic Olefin (TPO)
- Chlorinated Polyethylene (CPE)
- Polyvinyl Chloride (PVC)
- PVC Alloys or Compounded Thermoplastics
- Copolymer Alloy (CPA)
- Ethylene Interpolymer (EIP)
- Nitrile Alloys (NBP)
- Tripolymer Alloy (TPA)
The most common thermoplastic roof membranes are PVC (chemical weld) and TPO (heat weld). PVC is common simply because it was the frontrunner until TPO came into its own with more adopters. Thus, for this group, we will look at TPO when comparing single-ply roofing membranes.
TPO membranes are produced by calendering with lamination, extrusion with lamination, or extrusion-coating techniques. TPO sheets are a blend of polypropylene and ethylene propylene polymers and usually are reinforced with polyester. Note EPDMs main characteristics:
- Sheet widths range from 6 feet to 12 feet wide.
- Sheets are typically 40 millimeters to 100 millimeters thick.
- Seams are sealed by heat welding with hot air.
- TPO membranes commonly are white, but can allow for a colorant.
- Flame retardants are added.
- UV absorbers and other proprietary substances are added as needed.
Group 3: Modified Bitumen Membranes
These membranes combine asphalt with modifiers and reinforcement materials. They are often a ‘sandwiched’ roofing material. These materials can perform well, but they are not as advanced as the other two groups. Many roofers refer to modified bitumens as ‘torch-down’ roofs because a large flame-throwing torch melts the asphalt so that seams can be joined together.
There are two types of modified bitumen (MB) roofing membranes:
- SBS polymer-modified bitumen membranes commonly are installed via hot mopping asphalt (similar to BUR systems) or cold adhesive. Some SBS modified membranes are self-adhering and contain an adhesive backing.
- APP polymer-modified bitumen membranes typically are heat-welded or torch-applied. Consumers should be cautioned that NRCA does not recommend torch-applying a modified bitumen membrane sheet directly to a wood deck.
Generally, APP modifiers impart a ‘plasticized’ quality to asphalt, and SBS modifiers impart a ‘rubberized’ quality to asphalt. MB membranes and EPDM, a thermoset membrane, often are confused by consumers because of colloquialisms used by roofing contractors. MB and EPDM membranes are sometimes called “rubber roofs.”
Modified bitumen is inexpensive, easy to apply in the case of SBS, and great for DIY types. This combines with its short lifespan make it a non-competitor for larger commercial roofing spaces.
Comparing TPO & EPDM
These two membrane types are the ones you’ve likely heard the most about. If you have a low-slope (flat) commercial roof, it most likely has a leading thermoset or thermoplastic membrane on it. Our head-to-head comparison takes into account a range of good-to-top tier products per each single-ply membrane type. We awarded each a +1 or -1 to give a final tally of overall prowess of each membrane type, if it gave more options or value, or had a deficit or negative detractor.
| ——————– | EPDM | TPO |
| Warranty Timespan | 10-35 Years | 10-35 Years |
| Warranty Value | Average | Wide |
| Cost Effective | Yes | Yes |
| Lifespan | 20-50 Years | 15-50 Years |
| Thickness | 45-60 Millimeters | 40-100 Millimeters +1 |
| Maintenance Costs | Medium -1 | Low |
| Energy Savings | Little to None | Light to Significant +1 |
| Summer Heat Buildup | Yes -1 | Little |
| Suitable Climate | Colder -1 | Most |
| Environmentally Friendly | Yes: Recycled Materials | Yes: 100% Recyclable |
| Color Options | Black & White | Many +1 |
| Inexpensive Repairs | Typically | Yes +1 |
| Track Record | Solid +1 | Short -1 |
| Sheet Size | Medium to Huge +1 | Small to Medium |
| Chemical Resistance | Very Poor -1 | Excellent +1 |
| Requires Skill to Install | Yes | Yes |
| Pollution From Runoff | None | None |
| Shrinkage With Heat | Some | Some |
| Failure After 10 Years | Moderate to Low -1 | Very Low to None |
| Installation Speed | Average | Below to Above Average -1 |
| Weather Rating | Average | Average to Very Good |
| Final Tally | -3 | +3 |
When we’re comparing EPDM and TPO products, we get a six-point spread in favor of TPO. As a GAF Master Elite roofing contractor, Stonewater Roofing uses the top-rated TPO lines made by GAF. When you combine the best products, top notch installations and the best warranty, TPO picks up two or three more points over EPDM.
Call the commercial roofing professionals at Stonewater Roofing to learn more about upgrading your flat roofing to a TPO membrane from GAF. We can perform a free in-depth inspection of your roof, let you know its condition and provide a free estimate for its replacement.