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When should ladder-type joint reinforcement be used and when should truss-type joint reinforcement be used?


Although the Specification for Masonry Structures, TMS 602-11/ACI 530.1-11/ASCE 6-11, does not provide guidance on which type of joint reinforcement to use, the Building Code Requirements for Masonry Structures, TMS 402-11/ACI 530-11/ASCE 5-11, prohibits using truss-type joint reinforcement to connect the wythes in non-composite masonry walls (multi-wythe walls with a non-mortared and non-grouted collar joint).    While ladder-type joint reinforcement can be used anywhere, there is another condition under which truss-type joint reinforcement should not be used.

The diagonal cross wires of truss-type joint reinforcement will interfere with placement of vertical reinforcing bars relative to the tolerances of the Specification for Masonry Structures and can inhibit grout flow.  Therefore, truss-type joint reinforcement should not be used in vertically reinforced single or multi-wythe masonry walls.  Ladder-type joint reinforcement may be used, but the cross-rods should be specified to be spaced at 16 inches on center. Some manufacturers produce joint reinforcement with cross-wires at a non-modular spacing, which can also interfere with placement of grout and vertical reinforcement.

The only type of construction in which truss-type joint reinforcement is preferred is in single wythe concrete masonry that is not vertically reinforced.  The truss-type joint reinforcement is stronger than ladder-type in axial tension and better able to resist the tensile stresses that develop from shrinkage of the concrete masonry.

The decision to utilize this information is not within the purview of the MIM, and persons making use of this information do so at their own risk.  MIM makes no representation or warranties, expressed or implied, with respect to the accuracy or suitability of this information.  MIM and its members disclaim liability for damages of any kind, including any special, indirect, incidental, or consequential damages, which may result from the use of this information.  This information is not to be interpreted as indicating compliance with, or waiver of, any provision of any applicable building code, ordinance, standard or law.