Question:
Is a couple allowed to sit on the same couch while she is a niddah. The couch has separate sitting and leaning cushions
Answer:
If the couch has separate cushions and they cannot feel the other ones movements, then it is permitted. Sometimes however if there is a mattress of springs underneath the cushions, then when one moves the other will feel their movements.
Sources:
Shiurei Shevet Halevi 195-5 (11) D:H B’safa.