Materials: Masonry Units, Mortar, Grout, Reinforcement, and Accessories
Units
Load-bearing concrete masonry units must meet ASTM C90, with a minimum net-area compressive strength of 2,000 psi. Facing brick is ASTM C216, graded SW, MW, or NW for weathering. Hollow brick is C652; building brick is C62. Verify grade, type, dimensions, and absorption or saturation coefficient where specified.
Mortar and grout
ASTM C270 mortar types are M (2,500 psi), S (1,800 psi), N (750 psi), O (350 psi), and K (75 psi) under the property specification. Type M is highest strength; N is common for interior or non-seismic work; S is used for moderate requirements; O is low strength. Grout must meet C476, with a minimum 28-day strength of 2,000 psi.
Reinforcement and accessories
Deformed reinforcement must meet ASTM A615/A615M or A706; joint reinforcement wire meets A951; anchors and ties are galvanized to A153 or otherwise protected. Flashing, weep holes, and movement joints are accessories that must match approved submittals.
Worked example
A submittal offers Type N mortar where drawings require Type S. Type N property-spec strength is 750 psi versus 1,800 psi for Type S. Even if the mason argues that N is easier to work, the inspector must reject it unless an approved revision shows the design was checked for the lower strength.
Traps
- Using gross rather than net area for CMU strength.
- Assuming mortar type is interchangeable without design approval.
- Accepting uncoated ties in exposed locations.