Yes, You need to provide a joint with KEY and rebars crossing the joint. The spacing of joint depends on the thickness and plan size of the raft. Also, per good detailing practice, provide a waterstop across the key to avoid moisture ingress.
you have to provide key construction joint and reinforcement have to continue whether with overlap or couplers system,key joint should be roughened and water stop bars to be provided.location of construction joint to be agreed from with the designer of the raft to determine where are the best locations to avoid the max moments and shear forces.
construction joints in raft foundation 
Re: construction joints in raft foundation
