There are different types of low-slope roof membranes and you should be aware of the difference between them. Understanding the materials and differences between membranes makes for more efficient maintenance and upkeep so you can get the best out of your roof.
What Do You Need To Know About Low-Slope Roof Membranes?
TPO roof membranes are usually all white and can be attached a number of ways. They can be ballasted, mechanically attached or fully adhered although the majority is mechanically attached. TPO has become more common in the industry over the last few years because of its thermoplastic properties. This membrane also has seams that are welded together to provide a mostly homogeneous membrane.
PVC membranes are similar in appearance to TPO membranes and are also usually a shade of white. They also are thermoplastic but are more pliant than TPO membranes as they conform with substrate changes more readily.
EPDM is a black synthetic rubber roof membrane and there are several methods of securing these. One method uses large stones or concrete pavers (ballast) to cover the EPDM membrane.
The ballast weight secures the above-deck roof insulation and roof membrane. If there is no ballast, then the system is mechanically attached or adhered. If you drag your foot across the membrane and it wrinkles, then the system likely is mechanically attached. An adhered system is different and will show the joints in the substrate. EPDM membranes typically are joined at the seams with two-sided adhesive tapes. If a roof system is not a single-ply roof membrane, then it is most likely a bituminous membrane. Bituminous membranes are usually built-up roof (BUR) membranes or polymer-modified bitumen membranes. They can be hot asphalt-applied or coal tar pitch membranes.
These systems are also multi-ply roof systems, constructed on the roof by a roofing crew. BUR membranes are most often surfaced with bitumen and gravel, mineral-surfaced cap sheets or a liquid-applied roof coating. Polymer-modified bitumen membranes have an unsurfaced base layer of polymer-modified bitumen membrane adhered to a substrate. The three most common application methods for polymer-modified bitumen membrane are hot (asphalt)-applied, cold (adhesives)-applied, or torch-applied. You can also choose to apply a protective aluminum coating, over the cap sheet.
Once you know the differences between the available low-slope roof membranes, you can make an informed decision about roofing maintenance and design. Just be sure to discuss everything with your roofing professional first.