The skill comes in growing the house. Bigger houses need bigger hallways, wider kitchens, tables for christmas and sofas for a gaggle. They need more to provide more toilets, to handle more ironing and store more shoes.
We often find ourselves removing bad extensions - additions with low ceilings and poor light levels, which not only squander the opportunities but actively blight the original house. If the circulation and daylight are not resolved, the rooms now stranded in the middle of the house can just become dark thoroughfares.
They are like an old hedge - the outer bits may look OK but the middle is lifeless.