Generational homes used to be normal, but families got away from that concept decades ago. The children began moving out as soon as they were through with schooling, and eventually the couple sold their house or gave it to someone else in the family. Modern life has changed that in some cases, but finding room for parents could be difficult. Adding the mother-in-law suite has become a good way to gain space for every generation of a modern household.
The complexity of the suite often depends upon the family situation. Some parents want their own kitchen and bathroom, and they might even prefer a living area to entertain guests. A door to the outside and their own parking area could also be on their wish list. Other parents would rather have only their own bedroom and bath, and they would prefer to eat with the family. Their accommodations might be easier to make in the beginning, but they could find later they feel restricted when it comes to entertaining.
Each generational home will find their own needs are what will drive the design and the size of the addition. Accommodating every person might not be possible, but designers and construction companies can do quite a lot for a reasonable amount of money. It is an investment in future happiness, so most families are willing to work hard to get what they really need.
A mother-in-law suite has a few other advantages that have little to do with in-laws, and it can function as a way to let adult children have their own space within the home. They might not quite be through schooling, or they could have a job and be saving for their own home. The need to be treated as adults can be satisfied by allowing them to use the suite instead of their childhood bedroom.