Stack bond is one particular bond pattern that falls into the category of “not laid in running bond”, where running bond is defined as placing units in successive courses so that head joints are offset at least one-quarter the unit length. The Code does require horizontal reinforcement when the masonry is not laid in running bond. These Code requirements apply to concrete masonry, clay masonry, and dimension stone masonry, but not autoclaved aerated concrete masonry. Cast stone masonry is also currently excluded from the Code, but the same amount of horizontal reinforcement should be used when cast stone is not laid in running bond.
Masonry that is not laid in running bond is required to contain horizontal reinforcement in the amount of 0.00028 multiplied by the gross vertical cross-sectional area of the wall, using specified dimensions. The horizontal reinforcement may be placed in mortar joints or in bond beams, and may be spaced up to 48 inches on center (MSJC 2011 Section 1.11). Standard (W1.7 or 9 gauge) two-wire joint reinforcement placed at 16 inches on center in mortar bed joints of nominal 8-inch thick masonry satisfies this requirement.
Masonry veneer that is not laid in running bond is required to have horizontal joint reinforcement consisting of at least one wire of size W1.7 spaced at a maximum of 18 inches on center (MSJC 2011 Section 18.104.22.168).
- Building Code Requirements for Masonry Structures, TMS 402-11/ACI 530-11/ASCE 5-11, Masonry Standards Joint Committee (MSJC)
- National Concrete Masonry Association (NCMA), TEK Note 10-3, 2003, Control Joints for Concrete Masonry Walls – Alternative Engineered Method
- National Concrete Masonry Association (NCMA), TEK Note 14-6, 2004, Concrete Masonry Bond Patterns
- National Concrete Masonry Association (NCMA), TEK Note 14-18B, 2009, Seismic Design and Detailing Requirements for Masonry Structures
- National Concrete Masonry Association (NCMA), TEK Note 12-2B, 2005, Joint Reinforcement for Concrete Masonry
- Brick Industry Association (BIA), Technical Notes 30, March 1999, Bonds and Patterns in Brickwork
- Troubleshooting Masonry, Q&A: Reinforcing Stack Bond, Masonry Construction Magazine, December 1991, page 460
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