Masonry Units and Materials
Clay bricks and concrete masonry units are the primary materials used in masonry wall construction. Clay bricks are manufactured by firing molded clay at temperatures above 1,800 degrees Fahrenheit, producing a durable unit with compressive strengths ranging from 3,000 to 20,000 psi. Concrete masonry units, commonly called CMUs or concrete blocks, are manufactured from Portland cement, aggregates, and water, cured under controlled conditions to achieve specified strengths. Standard CMU dimensions are 8 by 8 by 16 inches, providing a nominal 8 inch wall thickness with mortar joints.
Mortar is the binding agent that bonds masonry units together and seals the wall against air and moisture penetration. Type N mortar with a compressive strength of 750 psi is suitable for most above-grade applications. Type S mortar at 1,800 psi is used for below-grade walls and structures requiring higher strength. Grout is a fluid mixture of cement, aggregate, and water used to fill voids in reinforced masonry for bonding reinforcement to the masonry.
Bond Patterns
The running bond pattern with overlapping units at half-length spacing is the most common and structurally efficient pattern. Stack bond with units aligned vertically requires horizontal reinforcement to develop adequate strength. Common bond incorporates a course of headers every fifth or sixth course. Flemish bond alternates stretchers and headers in each course. horizontal joint reinforcement for masonry walls. chimney flue liner installation requirements. The choice of bond pattern affects both the appearance and structural performance of the wall, with running bond providing the best lateral load resistance.
Reinforcement and Grouting
Horizontal reinforcement consisting of joint reinforcement or bond beams is placed at specified intervals to control cracking and improve lateral load resistance. Joint reinforcement consists of prefabricated ladder or truss-type wires embedded in the mortar joints. Bond beams are horizontally reinforced courses filled with grout to create continuous reinforced elements at floor and roof levels. Vertical reinforcement in grouted cells provides resistance to bending and axial loads. The grout must be consolidated by rodding or vibration to fill all voids around the reinforcement.