This is similar to economy scaling that you must have practiced in the section above. If six (6) were inadequate and as such; you will need to have about 16 built. If it happens that 16 workers aren’t adequate then you will need to raise the number to 24. Also, when there aren’t enough gateways or barracks then you may need to have more built. Production need to scaled up in other for income rate to be matched. There is only one way to achieving this which is to have your economy scaled up.
Having additional structures built while expecting more expansion makes you more effective. This is because translation to higher and more effective production becomes very easy. By now, you should have knowledge of the limit which is required for everything to be built.