Corpus sync: neutrality remakes, note hygiene, datasheet relocation, transformer-split cross-refs
---
title: Concrete Masonry Units
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### Hollow units (net area less than 75% of gross area) shall be the standard configuration for general loadbearing and partition masonry.
−### Solid units (net area 75% or more of gross area) shall be furnished where the structural Drawings require solid net section for compressive capacity, or where the units are exposed to freeze-thaw or below-grade conditions calling for solid section.
−
−## A hollow unit is "solid-grouted" by filling its cells with masonry grout in the field; that is an assembly operation, not a property of the unit. Do not confuse a solid unit (a casting with little or no cell void) with a grouted hollow unit — they are specified differently and the grouting belongs to [[sync/unit-masonry]]. {note}
−
```datasheet
label: Unit configuration
…5 unchanged lines
```
+### Solid units (net area 75% or more of gross area) shall be furnished where the structural Drawings require solid net section for compressive capacity, or where the units are exposed to freeze-thaw or below-grade conditions calling for solid section.
+
+## A hollow unit is "solid-grouted" by filling its cells with masonry grout in the field; that is an assembly operation, not a property of the unit. Do not confuse a solid unit (a casting with little or no cell void) with a grouted hollow unit — they are specified differently and the grouting belongs to [[sync/unit-masonry]]. {note}
+
# Weight Classification {toc}
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# Dimensions and Configuration {toc}
−## CMU is specified by nominal dimension (width by height by length). Actual dimensions are 3/8 in. less than nominal in each direction, so the unit plus one mortar joint courses out to the nominal module. An 8x8x16 nominal unit measures 7-5/8 by 7-5/8 by 15-5/8 in. The 8x8x16 unit is the dominant module across virtually all producers and is the 80% default for structural walls. {note}
+## CMU is specified by nominal dimension (width by height by length). Actual dimensions are 3/8 in. less than nominal in each direction, so the unit plus one mortar joint courses out to the nominal module. An 8x8x16 nominal unit measures 7-5/8 by 7-5/8 by 15-5/8 in. The 8x8x16 unit is the dominant module across virtually all producers and the standard choice for structural walls. {note}
### Units shall be furnished in the nominal width scheduled for each wall type, coursing on the modular grid established by the Drawings.
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### Cell size shall provide the minimum clear grout space required by TMS 602 for the specified grout type and lift, accounting for the actual face-shell and web projections of the unit furnished.
−### Fine grout to ASTM C476 requires a smaller minimum clear cell dimension than coarse grout; selecting a coarse grout against a unit whose cells provide only fine-grout clearance produces rejected submittals or forced re-design, so verify the cell against the grout before specifying. {note}
−
```datasheet
label: Grout type the cells must accommodate
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```
+### Fine grout to ASTM C476 requires a smaller minimum clear cell dimension than coarse grout; selecting a coarse grout against a unit whose cells provide only fine-grout clearance produces rejected submittals or forced re-design, so verify the cell against the grout before specifying. {note}
+
# Specialty Shapes {toc}
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### The finish scheduled for each exposed wall type shall be furnished, matching the accepted mock-up panel for that finish.
−### Integral color shall be achieved with pigments batched into the mix; surface-applied coatings shall not be used to simulate integral color on exposed units.
−
−### The delivery schedule shall account for the lead time of the finish selected.
−
−### Ground-face and other specialty finishes may carry longer manufacturing lead times than standard units. {note}
−
```datasheet
label: Surface finish (exposed units)
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```
+### Integral color shall be achieved with pigments batched into the mix; surface-applied coatings shall not be used to simulate integral color on exposed units.
+
```datasheet
label: Integral color
…5 unchanged lines
```
+### The delivery schedule shall account for the lead time of the finish selected.
+
+### Ground-face and other specialty finishes may carry longer manufacturing lead times than standard units. {note}
+
# Physical Properties {toc}
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### Loadbearing units shall have a minimum average net-area compressive strength of 2,000 psi (13.8 MPa) for an average of three units, with no individual unit below 1,800 psi (12.4 MPa), per ASTM C90.
−### Where the structural Drawings specify a unit strength higher than the ASTM C90 minimum to achieve the required f'm, the higher specified value shall govern.
−
−## Typical specified f'm for standard reinforced CMU walls falls between 1,500 and 2,000 psi, with 1,500 psi common for lightly loaded structures and 2,000 to 3,000 psi where special inspection and higher demand apply. The unit strength is selected to satisfy the f'm by the unit-strength method or the prism-test method of TMS 602. {note}
−
```datasheet
label: Minimum net-area compressive strength (avg of 3 units)
…6 unchanged lines
```
+### Where the structural Drawings specify a unit strength higher than the ASTM C90 minimum to achieve the required f'm, the higher specified value shall govern.
+
+## Typical specified f'm for standard reinforced CMU walls falls between 1,500 and 2,000 psi, with 1,500 psi common for lightly loaded structures and 2,000 to 3,000 psi where special inspection and higher demand apply. The unit strength is selected to satisfy the f'm by the unit-strength method or the prism-test method of TMS 602. {note}
+
## Absorption
### Maximum water absorption shall comply with ASTM C90 for the weight class furnished: 13 pcf for normal weight, 15 pcf for medium weight, and 18 pcf for lightweight units.
−### Lower absorption improves resistance to moisture penetration and efflorescence on exposed walls. {note}
−
```datasheet
label: Maximum absorption (per weight class)
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```
+### Lower absorption improves resistance to moisture penetration and efflorescence on exposed walls. {note}
+
## Linear drying shrinkage
### Total linear drying shrinkage shall not exceed 0.065% when tested per ASTM C426, as required by ASTM C90.
−### On projects in hot, dry climates, shrinkage test data confirming a margin below 0.065% should be obtained rather than accepting units at the limit.
−
−### Units near the shrinkage limit placed in hot, dry climates are prone to cracking at control joints and at the corners of openings. {note}
−
```datasheet
label: Maximum linear drying shrinkage (ASTM C426)
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```
+### On projects in hot, dry climates, shrinkage test data confirming a margin below 0.065% should be obtained rather than accepting units at the limit.
+
+### Units near the shrinkage limit placed in hot, dry climates are prone to cracking at control joints and at the corners of openings. {note}
+
## Dimensional tolerances
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### Where a fire-resistance rating is required, the unit density class and configuration furnished shall provide the equivalent thickness needed for the rating by the calculated method, or shall match the units of the listed tested assembly.
−### Where a rating is achieved through a listed (UL or equivalent) assembly, the grout-fill pattern of that listing shall be followed exactly.
−
−### Substituting "solid grout all cells" for a partially grouted listed assembly, or vice versa, voids the listing. {note}
−
```datasheet
label: Fire-resistance rating required
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```
+### Where a rating is achieved through a listed (UL or equivalent) assembly, the grout-fill pattern of that listing shall be followed exactly.
+
```datasheet
label: Rating basis
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```
+### Substituting "solid grout all cells" for a partially grouted listed assembly, or vice versa, voids the listing. {note}
+
# Testing {toc}
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## Foundation bearing and frost-depth requirements supporting CMU loadbearing walls are governed by [[sync/shallow-foundations]]. {note}