SpecTopics: Understanding ASTM Standards for Roofing Membranes

ASTM International, formerly known as American Society for Testing and Materials, the world’s largest developer of standards, is an international organization that develops and publishes voluntary, consensus-based technical standards for a wide range of materials, products, systems, and services.

When it comes to single-ply roofing membranes, the following are the primary standards for each membrane type:
TPO – ASTM D6878 Standard Specification for Thermoplastic Polyolefin Based Sheet Roofing
EPDM – ASTM D4637 Standard Specification for EPDM Sheet Used in Single-Ply Roof Membrane
PVC – ASTM D4434 Standard Specification for Poly(Vinyl Chloride) Sheet Roofing

Each of these standards was reviewed and approved by the entire ASTM membership, which includes roofing membrane manufacturers, building scientists, consultants, and raw material suppliers.

When reviewing or comparing products with properties tested to a prescribed standard, it’s helpful to understand how these standards are constructed and organized for accurate comparisons and/or product selection.

At a high level, each of the single-ply standards listed above can be thought of as the overarching guidelines for the designated membrane. The standard prescribes minimum performance or physical property requirements and refers to more specific ASTM standards or test methods that outline how to test a given property or characteristic of the membrane.

The following are some examples of specific testing standards which will be referenced in the membrane test standard:
- ASTM D7635 Standard Test Method for Measurement of Thickness of Coatings Over Fabric Reinforcement
- ASTM D751 Standard Test Methods for Coated Fabrics
- ASTM D1004 Standard Test Method for Tear Resistance (Graves Tear) of Plastic Film and Sheeting
- ASTM D2136 Standard Test Method for Coated Fabrics – Low-Temperature Bend Test
- ASTM D1204 Standard Test Method for Linear Dimensional Changes of Nonrigid Thermoplastic Sheeting or Film at Elevated Temperature

The following is an example of a membrane test referencing another specific test standard:
The PVC membrane standard – ASTM D4434 – requires membranes to have a minimum of 16 mils (.40 mm) of material over the scrim (thickness over scrim). The standard states that test method ASTM D7635 must be followed to take this thickness over scrim measurement. This second standard – D7635 – specifically outlines the equipment and procedures that should be used for measuring thickness over scrim. This standard will then likely reference several other ASTM standards that are to be followed based on the testing procedures to prevent rewriting procedures that already exist.

In the example described above, one manufacturer may list a thickness over scrim measurement in accordance with D4434, and another may list it in accordance with D7635. Technically, both were tested to the exact same standard.

What is important to understand is that these ASTM standards are organized into a hierarchy. When comparing test results, look for the reference to the primary membrane standard to trust that each of the appropriate tests were followed as detailed in the overarching membrane standard.

For more information on specific tests for membranes, refer to their Product Data Sheets which list typical properties and characteristics for the specific membrane. Product Data Sheets for a few membranes are linked below:
TPO (Reinforced)
EPDM (Non-Reinforced)
PVC (Reinforced)

Contact Taylor Gingerich with questions.