New buildings give birth to more settlers. Your happiness level corresponds to the number of inhabitants in your village and cannot be lower than it. So to build a construction, first you need to reach a certain happiness level fitting the amount of villagers this construction will provide your island with. For example, to build a new villa that will add 3 villagers, your happiness level must be at least 3 levels higher than the current number of your population.
Why do the requirements for happiness level always increase when I want to build a new house?
Last Updated: 50d