The International Building Code or IBC is a set of advised international building codes. Whether a country accepts these building codes is up to them, but there are many elements of construction which are outlined in the building codes, including the ceiling heights. The International Code Council (ICC), managers of the IBC, have also suggested a number of different codes including the International Residential Code or IRC.
The IRC has changed their building plan advice throughout the years, so this can make understanding the information in the building codes very confusing. Search on the Internet to find the latest version of the code so that you can build your home to the highest standards.
2006 International Residential Code
The latest version of the residential code issued by the ICC is the 2018 International Residential Code. This has a number of regulations which set restrictions on the minimum size of rooms and the heights of ceilings. For instance, there has to be a minimum of one room in the property which is at least 120 sq feet in size. All of the other rooms in the house except for the kitchen need to be a minimum of 70 sq feet. Anything like a hall, or bathroom is excluded from these size restrictions.
The 2018 International Residential Code is simply the latest version of these codes, which are built upon the foundation of the old code bodies. It is important before beginning any project to confirm which version of the IRC, or previous code, is currently being used in your municipality.
Minimum Ceiling Height
The 2018 International Residential Code also dictates a minimum ceiling height requirement. Normally, you need to have at least a 7-foot, 6-inch ceiling height. If there are any beams in the ceiling then these can be 6-feet, 6-inches above the floor as long as they are spaced at least 4 feet apart.
If you have any basements or other spaces which are not habitable, then the ceiling can be 7 feet high as these are not considered living spaces. When converting a previously non-habitable space into a room, however, you will need to think about bringing your ceiling heights up to code if they aren't already.
If a room has any sloped ceiling, then a minimum of half the ceiling must be at least 7-feet, 6-inches high.
The ceiling height restrictions in a bathroom are different. The prescribed minimum height needs to be 6-feet, 8-inches, but only where the fixtures are. There needs to be a large enough area for a showerhead, which is at this height. This is what allows half bathrooms to be installed under the stairs as the entire room does not need to be the same height.
Just to summarize, the minimum ceiling heights suggested by the latest 2018 IRC state that any corridors and habitable spaces must a minimum be 7-feet, 6-inches high. Any non-habitable areas such as kitchens, bathrooms, storage areas, and laundry rooms can have heights of 7 feet. Sloped ceilings must only meet this requirement for half the room, and bathrooms only have to meet a minimum 6-foot, 8-inch height around fixtures, not throughout the room.
Obviously ICC codes will continue to update and get more refined as new technology emerges and as dangers with lack of construction regulation reveal themselves, so always research before undertaking a construction project for yourself to be sure your information is up-to-date.