Many two-story homes in California have ceilings that are high enough to be converted into new rooms. These high ceiling room conversions are also known as "loft additions". However, this does NOT mean you are limited to just building an open loft. High ceiling loft additions can be built into new bedrooms, new bathrooms, bonus rooms, home offices, theaters and more.
Above - BEFORE - high ceiling to be converted into a new loft addition and bedroom.
AFTER - New loft addition with coffer tray ceiling to raise the center of the new ceiling even higher than the original height in the other rooms.