How close can a reinforcing bar be to the side of the core and still have the grout flow around it?
The Masonry Standards Joint Committee Specification (ACI 530.1/ASCE6/TMS 602) in Section 3.4 C.1 of the 1995 edition (3.4 C.2 in the 1999 edition) and the Uniform Building Code in Section 2106.3.3 require that a 1/4-inch space be provided between the bar and the side of the cores or any face of a masonry unit for fine grout and 1/2-inch space for coarse grout as defined in ASTM C 476 "Standard Specification for Grout for Masonry." This requirement ensures that there is sufficient clearance for grout to surround reinforcing bars so that stresses are properly transferred. Also, steel reinforcing that is completely encased in grout will be protected by the grout.