21.406.2 Particular Feature Units

For particular feature units, dimensions shall be in accordance with the following:

1. For molded face units, no overall dimension (width, height and length) shall differ by more than ¹/₈ inch (3.2 mm) from the specified standard dimension. Dimensions of molded features (ribs, scores, hex-shapes, patterns, etc.) shall be within ¹/₁₆ inch (1.6 mm) of the specified standard dimensions and shall be within ¹/₁₆ inch (1.6 mm) of the specified placement of the unit.
2. For split-faced units, all non-split overall dimensions (width, height and length) shall differ by no more than ¹/₈ inch (3.2 mm) from the specified standard dimensions. On faces that are split, overall dimensions will vary. Local suppliers should be consulted to determine dimensional tolerances achievable.
3. For slumped units, no overall height dimension shall differ by more than ¹/₈ inch (3.2 mm) from the specified standard dimension. On faces that are slumped, overall dimensions will vary. Local suppliers should be consulted to determine dimension tolerances achievable.

Note: Standard dimensions of units are the manufacturer's designated dimensions. Nominal dimensions of modular size units, except slumped units, are equal to the standard dimensions plus ³/₈ inch (9.5 mm), the thickness of one standard mortar joint. Slumped units are equal to the standard dimensions plus ¹/₂ inch (13 mm), the thickness of one standard mortar joint. Nominal dimensions of nonmodular size units usually exceed the standard dimensions by ¹/₈ inch to ¹/₄ inch (3.2 mm to 6.4 mm).