Are there any breeds that should never be put together?

[Thechickentrainer1999]

What type of breeds would you not recommend putting together? Also would you recommend me combining smaller chickens like silkies with regular laying chickens?

 

[Folly's place]

I think that Silkies are difficult in many mixed flocks; many are kept in separate coops for their safety.
Production reds, which includes most hatchery RIRs, tend to be feather pecking and aggressive with their flockmates.
Salmon Favorelles are sweet and gentle souls who will get picked on, especially by those production reds!
I have both bantams and standard birds together, but I avoid all of the above, for those reasons. Someday I'd like to have the Favorelles again, but not right now.
Mary