How far should vertical reinforcing bars be lapped in a reinforced concrete masonry wall?
Lap lengths for reinforcing bars in masonry walls are listed in the ACI 530/ASCE 5 Building Code Requirements for Masonry Structures. The length of the lap depends on the diameter of the bar and the type of steel. The equation is .002 times the bar diameter times the allowable stress of the steel. No. 3 Grade 60 bars should be lapped 18 inches; No. 4 should be lapped 24 inches; No. 5, 30 inches; No. 6, 36 inches; No. 7, 42 inches; and No. 8, 48 inches. Be aware, however, that lap lengths are established in local building codes, which may not match the 530 requirements. Always check the requirements of the applicable code before specifying lap lengths.