@AlMcK Allan you need the bees to build up to bursting and good production of brood before putting the super on.
If you put a super on a weak hive they have to keep the area warm and will waste resources and time just keeping it warm.
Foragers are the nurse bees after they have helped bring up the brood if there is not a big enough work force to begin with they will have no real work force to replace them as nurse bees.
8 good frames of brood before putting on the supers