Frequently Asked Questions About Polypropylene Siding


1. What is the VSI Product Certification Program?

Since 1998, manufacturers have been able to certify that their vinyl siding products and, later, colors meet or exceed ASTM standards through the VSI Product Certification Program. In 2010, VSI added polypropylene siding to its certification program, allowing participating manufacturers to certify, with independent third-party certification, that their polypropylene siding meets or exceeds the ASTM D7254 Standard Specification for Polypropylene (PP) Siding.

2. What is ASTM?

ASTM International is one of the largest voluntary standards development organizations in the world for materials, products, systems, and services. Known for high technical quality and market relevance, ASTM International has helped guide product design, manufacturing, and trade in the global economy for more than 100 years.

ASTM D7254 Standard Specification for Polypropylene (PP) Siding is one of the technical standards for products developed by some of the more than 30,000 ASTM members, who represent producers, users, consumers, government, and academia. The ASTM D7254 standard includes performance tests for impact resistance, weathering, windload resistance, and flame spread.

3. How does the certification process work?

VSI’s third-party Administrator, Architectural Testing, Inc. (ATI), an accredited quality control agency, conducts twice yearly, unannounced inspections and additional tests to evaluate polypropylene siding products for adherence to ASTM D7254, including tests for:

  • Weatherability
  • Impact resistance
  • Windload resistance
  • Flame spread

4. What is the goal of polypropylene siding certification?

The goal of polypropylene siding certification is to set a benchmark for minimum polypropylene siding performance and to foster continued improvement as product performance and technology advance.

5. Why is it important to certify polypropylene siding?

Manufacturers of polypropylene siding may say they meet the performance requirements of ASTM D7254, but only products certified through VSI’s Program have been verified by an independent, accredited quality control agency to meet or exceed ASTM D7254.

6. What does polypropylene siding certification mean for homeowners?

Not only does polypropylene siding certified through VSI’s Program meet or exceed the industry standard for performance (ASTM D7254), but it also has been verified by an independent, accredited quality control agency to:

  • Weather the elements over time without cracking, chipping, flaking, pitting, or peeling.
  • Meet impact resistance requirements.
  • Withstand wind pressures equivalent to 110 mph or more.
  • Demonstrate flame spread performance equivalent to or better than wood materials commonly used in building construction.

7. How can you identify certified polypropylene siding products?

VSI has created a Label and Logo for certified polypropylene siding, which can be found on product promotional literature, websites, and packaging. VSI’s Official List of Certified Products allows customers to search and verify certified siding and is updated regularly.

8. How does VSI ensure that certified products remain in compliance withASTM D7254?

ATI conducts twice yearly, unannounced inspections at polypropylene siding manufacturing plants to ensure compliance with the standard. Should a product fail to meet the requirements, it will be removed from the Official List of Certified Products and will need to requalify before it can be put back on the list.

9. Is polypropylene siding different from vinyl siding?

Vinyl and polypropylene siding are two different types of polymeric siding, each with its own unique performance characteristics. Both can be certified through the VSI Product Certification Program with independent, third-party verification to meet or exceed the relevant ASTM performance standards.