Raising the Roof
When couples purchase their first home, they may buy one large enough for the family they have planned. Times change, and there could be times when all the planning in the world might not work well. For those families in need of more space, building on the ground floor might not be possible. They could run into zoning regulations where they are limited in area due to the size of their lot, but raising the roof could be just the outlet they need before the top blows off the building.
It will take extra bracing to add bedrooms and bathrooms to a second floor if the house was not originally constructed with one, but that could be a minor consideration. Pushing up the roof to add more room could be the best way to add interior space while keeping the original footprint of the house. It can be an expensive option, but it might be easier to live with than selling the old house and purchasing a new one.