R1003.3.2

Section R1003.3.2 is titled 'Horizontal reinforcing' and covers the requirement for the support of vertical reinforcing in masonry chimneys in seismic design categories D₀, D₁, and D₂. The horizontal ties shall be 1/4" cross-sectional area and set into the bed joints at no more than every 18" vertically. Where bends occur in the vertical reinforcment, two such ties shall be used. The purpose of this section is to assure the vertical reinforcement remains in place during the placement of the grout, maintaining the required grout coverage of the bars and thereby reducing the potential for premature degradation of the bars; with the ultimate goal of maintaining a structurally sound chimney in geographical areas subject to strong seismic activity.

The model shows a masonry chimney under construction, with the first level of horizontal support ties highlighted within the cells of the cement blocks.