Membrane
There are various types of rubber or plastic sheet-type single-ply membranes available for low-pitch and flat roof installations. Some are mechanically fastened and incorporate a slip-sheet or separation sheet, while others are fully adhered to the roof substrate. The PVC (polyvinyl chloride) and TPO (thermoplastic olefin) membrane seams are generally heat-welded using hot air, although there are self-adhering products available. The EPDM (ethylene propylene diene M-class) membrane seams are sealed using an adhesive and roller. Some of these products have built-in UV protection, while others require subsequent coatings as they age. These products offer the building owner and contractor a significant advantage in the area of lessened liability because they require no open flame on the roof. Some of the available membrane roof systems are:
| Type | Heat Welded | UV Protection | Ponding Water Exclusion | Manufacturer's Warranty (Years) |
| EPDM | No | No | Yes | 10 |
| PVC | Yes | Yes | No | 15 - 25 Commercial Lifetime - Residential |
| TPO | Yes | Yes | Yes | 10 |
Pros
No tear off required for mechanically fastened systems
Built-in UV protection for PVC and TPO products
Long warranty for PVC in residential applications
Ease of maintenance
No open flame on roof
Cons
Relatively high installation cost
High installation skill level for heat-welded products
Limited number of skilled installers
Short life expectancy for EPDM and TPO and products
The membrane roof systems are generally considered to be the most advanced roofing systems available for low-pitch and flat roofs. The PVC roof system in particular, with its ability to withstand ponding water and its resistance to UV rays, may well provide something that has been long missing from the flat roof industry –a permanent roof system. Although the up-front cost is clearly greater, it is difficult to overstate the value to the homeowner of removing themselves from the 10- to 15-year roof replacement cycle.
