NCCER Masonry cheat sheet

Mortar types by compressive strength (ASTM C270): Type M highest (2500 psi), then S (1800 psi), N (750 psi), O (350 psi), K (75 psi). Higher strength suits below-grade, high-wind, and severe weathering; lower strength suits interior non-load-bearing work.

Mortar proportion rule: cementitious materials plus lime total 1 part; sand is measured as 2.25 to 3 times that total. Type N field mix is commonly 1 cement : 1 lime : 6 sand; Type S is 1 cement : 0.5 lime : 4 to 4.5 sand.

Masonry cement is factory-blended cement plus plasticizer; portland-lime mortar is job-mixed. Do not add lime to masonry cement mixes unless the manufacturer's instructions allow it, and never add sand to preblended mortar.

Grout for reinforced masonry (ASTM C476) is a high-slump mix (8 to 11 in. slump) placed in lifts: fine grout in lifts not exceeding 5 ft, coarse grout not exceeding 12 ft 8 in., with consolidation by puddling or vibration.

Nominal vs. actual modular brick: 3 5/8 x 2 1/4 x 7 5/8 in. actual with a 3/8 in. joint gives 8 x 2 2/3 x 8 in. nominal. Course height rule: brick course height equals actual brick height plus joint thickness.

Concrete block modules: 8 x 8 x 16 in. nominal (7 5/8 x 7 5/8 x 15 5/8 in. actual). One standard block equals 8 in. of wall height and 16 in. of length; 1.125 blocks per square foot of wall face.

Wall tie and reinforcement rules: masonry wall ties spaced at 16 in. maximum vertically and 24 in. maximum horizontally for cavity walls; horizontal joint reinforcement commonly every other course (16 in. on center) and within 8 in. of openings.

Bond patterns: running bond offsets each course by half a unit; Flemish bond alternates stretcher and header in every course; English bond alternates full stretcher and full header courses; stack bond requires reinforcement because it has no overlap.

Flashing and weep rules: flashing extends up the backup at least 8 in. and laps the through-wall flashing; weeps are spaced at 24 in. maximum on center and immediately above flashing at the base of cavity walls.

Plumb tolerance for masonry walls: not more than 1/4 in. in 10 ft and not more than 3/8 in. total in any story; do not exceed 1/2 in. in any 20 ft of height for engineered work.

Level tolerance: individual courses level within 1/4 in. in 10 ft; bed joints of adjacent courses vary no more than 1/4 in. in thickness over 10 ft.

Mortar joint tooling: concave (V or round) tooling compacts the joint face and improves water resistance; struck or raked joints reduce weather resistance and are not acceptable on exterior walls in severe weathering.

Mortar field test: measure compressive strength on 2 in. cubes or 3 in. cylinders sampled from the mixer; slump for mortar is measured with a cone and typically 4 to 6 in. for masonry cement mixes.

Prism test: grouted masonry prisms verify compressive strength of the assembled system; prisms are built with the same units, mortar, and grout as the wall and cured under controlled conditions before testing.

Grout verification: slump test at the point of placement must fall in the 8 to 11 in. range; grout cubes are cast and tested at 28 days for the specified compressive strength (often 2000 psi minimum).

Anchor bolt and reinforcement inspection: verify diameter, embedment, and spacing against the drawings; check that bolts are set in grout, not mortar, and that rebar is tied and positioned before grouting.

Water penetration test: apply a spray rack at approximately 5 gal/hr per square foot for at least 4 hours on a 10 ft by 10 ft wall area and inspect the interior face for leakage.

Clean-down and final inspection: remove mortar smears with a masonry cleaner compatible with the unit, verify weep holes are open, and confirm flashing laps are correct before closing the wall cavity.