Castlerock partners with objective, third-party organizations that continuously test our products and verify that we meet the highest standards of performance, quality, value and safety.

The Vinyl Siding Institute (VSI) sponsors independent, unbiased testing, inspection and certification of vinyl siding performance. Castlerock siding has been certified under a VSI program to meet or exceed the rigorous battery of tests known as ASTM D3679, the accepted standard for vinyl siding quality.

Thanks to this certification program, you can rest assured that, when installed according to our instructions, Castlerock siding will meet or exceed industry standards for quality and performance. You can also be confident that your siding will maintain a uniform color over time, lay straight on a flat wall and withstand the effects of normal seasonal temperature fluctuations.

UL Classified is a name consumers have come to trust over the generations. Products that display the Underwriters Laboratories logo have been strenuously tested to ensure that they are safe for everyday use.

Underwriters Laboratories applies these same safety considerations to manufacturers of building materials, including vinyl siding. We voluntarily submit to annual UL testing and quarterly inspections to assure you that our siding products are UL Classified to ASTM E84.

StayRight™ PVC Stabilizers help to prevent heat degradation during the manufacturing process and after installation.