What are the minimum ceiling heights for a Class 1a dwelling?

For a Class 1a building, the NCC sets minimum ceiling heights by room type:

• 2.4 m in a habitable room such as a bedroom, living room, or study. [1]
• 2.1 m in a kitchen, laundry, bathroom, sanitary compartment, hallway, or other non-habitable room. [1]
• 2.1 m measured over a stairway or ramp, and to any landing. [1]

Where a room has a sloping or stepped ceiling, the required height only needs to be met over the portion of the room used for the relevant purpose, so low areas under a rake can be discounted. [1]