Paver bedding sand — screed a uniform 1″ over a compacted base, never level the base with sand
Sand is a setting bed, not a fill. Leveling a low base with 2–3″ of sand (left) lets the bed consolidate unevenly, so pavers rut and pond water. The fix (right): compact the aggregate base to grade first, then screed a constant 1″ of ASTM C33 bedding sand (ICPI Tech Spec 2). Fix the grade in the base, not the sand.
What this diagram shows
A wrong-versus-right cross-section of paver bedding sand. On the left, sand is used to level a low, dished aggregate base: the bedding runs 2 to 3 inches deep in the dip, and because deep uncompacted sand consolidates unevenly under traffic, a paver over it tips, ruts, and ponds water in a birdbath. On the right, the aggregate base is compacted flat to grade first, then a thin, uniform 1-inch screed of ASTM C33 bedding sand is laid over it, so the pavers land level. The rule per ICPI Tech Spec 2 is to fix the grade in the base and screed a constant 1 inch of sand — sand is a setting bed, not a fill.
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