Brick, Block, and Mortar, Masonry

Masonry Units and ASTM Standards

Masonry units used in California must comply with ASTM standards adopted by the California Building Code (CBC) Chapter 21. For clay masonry, ASTM C62 governs building brick, while ASTM C216 governs facing brick. In California's varied climate, Grade SW (Severe Weathering) is often required due to its ability to resist freeze-thaw cycles and maintain a minimum compressive strength of 3,000 psi. Grade MW (Moderate Weathering) may be used where less exposure is expected, requiring a 2,500 psi minimum. Concrete Masonry Units (CMU) must meet ASTM C90. The CBC requires these units to have a minimum net area compressive strength of 1,900 psi for load-bearing applications. Standard nominal sizes are 8x8x16 inches, but actual dimensions are 7-5/8 x 7-5/8 x 15-5/8 inches to accommodate a standard 3/8-inch mortar joint. Precise measurement is critical for modular coordination in California seismic designs.

Mortar Types and Application Properties

Mortar selection is critical for seismic performance and is governed by ASTM C270, as referenced in CBC 2103. Mortar consists of cement, hydrated lime, and sand. Type S mortar is the standard for California masonry, offering a minimum compressive strength of 1,800 psi. It is required for reinforced masonry, below-grade applications, and structures in Seismic Design Categories D, E, and F. Type M mortar provides 2,500 psi and is used for high loads or masonry in contact with earth, such as retaining walls. Type N mortar (750 psi) is generally restricted to non-load bearing interior walls or veneer. Per Cal/OSHA Title 8, Section 1505, workers must be protected from silica dust during mixing. Mortar must be used within 2.5 hours of the initial addition of water; if it begins to stiffen due to evaporation within this window, it may be retempered once, but never after the 2.5-hour limit has passed.

Grout Requirements and Pouring Standards

Grout is distinct from mortar; while mortar bonds units, grout fills the voids (cells) to create a solid structural mass and bond to steel reinforcement. CBC 2103.3 requires grout to meet ASTM C476. Fine grout is used when the smallest cell dimension is less than 2 inches, while coarse grout (containing pea gravel) is used for larger voids. The minimum compressive strength for grout must match the specified masonry strength (f'm) but cannot be less than 2,000 psi. Grout must have a slump between 8 and 11 inches to ensure it flows into every cavity without voids. When pouring grout, CBC remains strict on lift heights: grout lifts are restricted to 5 feet unless specific cleanout procedures and inspection protocols for high-lift grouting (up to 12.67 feet or even 24 feet in specific engineered scenarios) are satisfied. Cleanout openings are mandatory at the bottom of every pour exceeding 5 feet.

Seismic Reinforcement and Placement

Reinforcement is a cornerstone of California masonry due to high seismic activity. CBC Chapter 21 and ACI 530 mandate that all masonry in Seismic Design Categories D and above be reinforced. Horizontal joint reinforcement, such as ladder or truss-type wire, must be spaced no more than 16 inches on center vertically. Vertical rebar must be centered in the cells unless otherwise specified. A minimum clearance of 1/4 inch for fine grout or 1/2 inch for coarse grout is required between the bar and the interior masonry shell to ensure total encapsulation. When splicing rebar, a lap length of 48 bar diameters is a common baseline, though strictly governed by structural engineering calculations. All cells containing reinforcement must be fully grouted. Improperly placed steel or air pockets in the grout can lead to catastrophic failure during a seismic event.

Installation Practices and Tolerances

Proper masonry installation requires strict adherence to environmental and structural limits. Per CBC 2104, masonry must be laid in a running bond unless otherwise specified; if a stack bond is used, additional horizontal reinforcement is required at 16 inches on center. Bed and head joints must be a uniform 3/8-inch thick. Hollow units must be laid with full head and bed joints on the face shells. For solid units, the bed joint must be full, and head joints must be filled completely. During hot weather (above 90°F), masonry must be protected from drying too quickly to ensure hydration; this may involve fog-misting or covering with plastic. During cold weather (below 40°F), materials must be heated, and the finished work must be protected from freezing for at least 24 hours to prevent the ice crystals from destroying the mortar bond strength.

Cal/OSHA Safety and Site Standards

Safety for masonry contractors in California is governed by Cal/OSHA Title 8, Article 15. Scaffolding must be inspected by a competent person before every shift. Any scaffold over 7.5 feet in height requires standard guardrails (top rail at 42-45 inches, mid-rail, and toeboards). For masonry saws, water-fed blades or HEPA-filtered vacuum systems are required to comply with Table 1 of the Crystalline Silica Standard (Section 1532.3) to prevent worker exposure to hazardous dust. Masonry walls under construction are unstable; Title 8, Section 1722 requires a limited access zone whenever a masonry wall is being built. This zone must be equal to the height of the wall plus 4 feet and must run the entire length of the wall on the side without scaffolding. Walls over 8 feet in height must be adequately braced to prevent overturning until lateral supports are permanently in place.