Permeable interlocking concrete pavement (PICP) cross-section
PICP is the opposite of a sand-set patio: the joints are open and filled with No.8 chip stone (no sand), and the base is an open-graded No.57 / No.2 stone stack that stores rain and lets it infiltrate the subgrade through a geotextile.
What this diagram shows
A cross-section of a permeable interlocking concrete pavement (PICP) stack, which has no sand. From the top: open-graded pavers with wide joints filled with No.8 chip stone instead of sand; a 2-inch No.8 bedding-stone layer; a 4-inch-minimum No.57 base; an 8-to-12-inch-minimum No.2 open-graded subbase that acts as a water reservoir; a geotextile over the subgrade; and an uncompacted subgrade that lets water infiltrate. Arrows show rain soaking straight down through the open joints.
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