Lap length is the overlapping length of two reinforcement
bars. Reinforcement steel is available from 6 to 18 meters. If we need to
extend beyond that, we are connecting it with another steel bar. That
overlapping length is nothing but Lap Length.
Example:-
The diameter of bar is 28 mm,
Lap Length = 50 x 28
= 1400 mm
= 1400/1000 = 1.4 m