"My less strong hive was the one I had to shrink to a nuc in December due to a failing queen and wax moths and have nursed it back to a full deep. It's building honey stores and has about 3 frames of good pattern brood. It should be ready for a super soon though I am still a little reluctant because it's really only got 5-6 frames full of bees. Since there's a flow on do I just watch for back filling brood comb"
Tracey, I would add a box as soon as they have 8 frames combed. They won't build unless they feel they have the room to. They will get into a swarm mindset if there is a flow on and they feel cramped.