To create a half-level, click on the part you want to raise and go to its Properties.
Note: in order to raise a room, it must be closed by a wall, a partition, or an invisible limit.
To raise the room, specify the desired height in Elevation.
If you still want the room to touch the ground, add the height chosen in Elevation to the Slab thickness of the existing slab.
In the example chosen here, the elevation is 100 cm, so we add 100 cm to the 20 cm of slab or 120 cm so that the room touches the ground and there is no vacuum between the ground of the room and the exterior.
Your half-level is created.
Choose your door or your opening as well as your staircases to be able to access your half level.