Concrete Reinforcing Steel Institute – “Placing Reinforcing Bars”
Wall Construction page 11-11
“The horizontal and vertical bars are wired securely to each other at sufficiently frequently intervals to make a rigid mat. Tying is required depending on upon the size and spacing of bars, but not less than 3 ties to any one bar, and, in any case, not more than 4 to 6 ft apart in either direction”