Paver sand — two different sands: polymeric in the joints, ASTM C33 bedding under the pavers

A paver job uses two different sands. Fine polymeric sand (sand + polymer binder) fills the joints between pavers; a nominal 1″ bed of coarse ASTM C33 concrete sand — never mason sand — sets the pavers over a compacted gravel base. Swap them and it fails: polymeric hardens under the pavers, mason sand ruts.

A cross-section of a paver installation showing the two different sands that must never be swapped. Fine polymeric jointing sand (fine sand plus a polymer binder) fills the narrow joints between the pavers on top. Directly under the pavers is a nominal 1-inch bed of coarse ASTM C33 concrete sand — not mason sand, which is too fine and lets the pavers rut. Below the bedding sand is a compacted gravel base over the subgrade. Polymeric sand belongs only in the joints; used as bedding it hardens into a rigid, non-draining slab. — Source: ASTM C33 (bedding) / ASTM C144 (jointing base); ICPI/CMHA Tech Spec 2

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A cross-section of a paver installation showing the two different sands that must never be swapped. Fine polymeric jointing sand (fine sand plus a polymer binder) fills the narrow joints between the pavers on top. Directly under the pavers is a nominal 1-inch bed of coarse ASTM C33 concrete sand — not mason sand, which is too fine and lets the pavers rut. Below the bedding sand is a compacted gravel base over the subgrade. Polymeric sand belongs only in the joints; used as bedding it hardens into a rigid, non-draining slab.

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