Lap Table as per BS 8110-1:1997

Minimum laps: 

The minimum lap length to be ≥ 15Ø or 300mm and for fabric reinforcement ≥ 250mm. 

Design of tension laps:

The length should be at least equal to the design tension anchorage length necessary to develop the required stress in the reinforcement. Lap lengths for unequal bar Ø may be based upon the smaller bar Ø

The following provisions also apply: 

a) where a lap occurs at the top of a section as cast and the minimum cover < 2Ø, the lap length to be increased by a factor of 1.4; 

b) where a lap occurs at the corner of a section and the minimum cover to either face < 2Ø or, where the clear distance between adjacent laps < 75 mm or 6Ø, the lap length to be increased by a factor of 1.4; 

c) in cases where both conditions a) and b) apply, the lap length to be increased by a factor of 2.0. 

Design of compression laps: 

The length to be ≥ 1.25 x compression anchorage length. Lap lengths for unequal bar Ø may be based upon the smaller bar Ø.