Is it necessary to splice bed-joint reinforcement, or can consecutive sections simply be placed next to each other without splicing or overlapping?
For joint reinforcing to work effectively, it must be spliced. This is critical in reinforced masonry. The designer must satisfy applicable building codes regarding the length of lap splices. One such example is the Uniform Building Code in Section 2104.8, which permits splicing wire joint reinforcement by lapping within the same mortar joint or by overlapping the reinforcement in alternating bed joints. If the bed joint reinforcement is lapped within the same mortar joint, the lap must be 54 wire diameters in a grouted cell or 75 wire diameters in a mortared bed joint. The most common bed joint reinforcement used is No. 9 longitudinal wire. In grouted cells, No. 9 wire must be lapped 8 inches. In mortar joints, No. 9 wire must be lapped 12 inches. The cross wires should be removed so that there are 12 inches of uninterrupted wire on both ends of the wire reinforcement to be lapped. The wires on one side of the splice should be bent slightly inward so that the lap occurs in the same plane. The procedure is similar for heavier-gauge wire. For 3_16-inch wire, the lap should be 11 inches for grouted cells and 14 inches within the mortar joints. In running-bond masonry, bars also can be lapped in alternate bed joints. In this case, the bars must be lapped 54 diameters plus twice the spacing of the bed joints. For a No. 9 wire, with conventional concrete masonry units, the overlap of the bed joint reinforcing would have to be 24 inches. If the splices occur in locations of minimum stress (such as a point of inflection), they can be smaller, provided calculations confirm adequate strength. In unreinforced walls where the reinforcement is used for crack control, I recommend following the same procedures. The bed-joint reinforcement will not be effective in resisting cracking if it is spliced ineffectively.