Source: MASONRY CONSTRUCTION MAGAZINE

Should steel reinforcing be installed before the masonry is laid up or after the walls are complete? If the steel is installed first, do you thread the CMU over the bars as they are laid?

Procedures for constructing reinforced concrete masonry walls will vary depending on local practices, the amount of reinforcing, and building size or type. One common method in lightly reinforced masonry walls is to install the reinforcing bars and grout the masonry walls after the walls are complete. The Masonry Standards Joint Committee specification (ACI 530/ASCE 5/TMS 402) allows grout pours of 24 feet in height when the grouted cell is 3 by 3 inches for fine grout and 3 by 4 inches for coarse grout defined in ASTM C476. The grout pour will be made up with several grout lifts not exceeding 5 feet each. Therefore, by code, a 24-foot-high concrete masonry wall can be built before the reinforcing is installed. In some parts of the country, especially in heavily reinforced walls, the reinforcing bars may be positioned before the wall is built. In this case the wall would be constructed using "A" or "H" concrete masonry units. An "A-block" is a hollow concrete masonry unit with one end closed and the opposite end open. It is sometimes referred to as a "single open end block." The "H-block" is open on both ends. These units can be used to build the wall without having to string the unit over the bar from the top.

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