CMHA Releases New FAQ on Interlocking Concrete Pavers on Open-Graded Aggregates

HERNDON, Va. (March 17, 2026) — The Concrete Masonry & Hardscapes Association (CMHA) has released its new FAQ: “Installing Standard Interlocking Concrete Pavers on Open-Graded Aggregates,” establishing a research-backed position for one of the industry’s most popular, and debated, installation methods. Developed after three years of rigorous testing and evaluation, this resource provides guidance professionals can use to design, specify and build open-graded systems.

“Installing pavers over open-graded bases and bedding has grown in popularity for its drainage and frost-heave resisting benefits, but it has also raised questions about long-term performance,” said Rob Bowers, P.Eng., CMHA’s vice president of engineering, hardscapes.

“The use of dense graded bases are considered industry best practice, but the recommendations show open-graded base and bedding can be used as an effective alternate for some projects. This FAQ gives contractors and installers the confidence to specify and build with open-graded systems, knowing the guidance is backed by data, testing and long-term performance monitoring.”

What the Research Confirmed 

CMHA’s recommendations are based on full-scale load testing and monitored field sections that evaluated:

• Comparative results — Benchmarking open-graded systems against dense-graded bases for strength, settlement and long-term integrity.
• Joint behavior — Documented joint material settlement over the pavement’s life, which will require ongoing monitoring and possible maintenance.
• Hydraulic response — Open-graded aggregates used are minimally affected by water (30%–40% void space), allowing construction to proceed in wet weather and making it resistant to frost-heave movement.

The FAQ is available now on CMHA’s website: masonryandhardscapes.org/resource/pav-faq-002.

The Concrete Masonry & Hardscapes Association (CMHA) is the national trade association representing producers, contractors, suppliers and industry professionals in the concrete masonry and hardscapes industry. Through research, technical expertise and advocacy, CMHA advances the use, performance, and understanding of concrete masonry and hardscape products across North America