You only need to measure the primary area if you do not already know the primary area or gross living area. When you report area information, the number of square metres must be rounded to whole square metres, e.g. 285.75 square metres = 285 square metres.
The primary area is measured to the inside of the surrounding walls for the primary part of the dwelling. Internal walls between primary areas must be included. The ceiling height must be at least 1.9m and the width at least 60cm. In the case of areas with a sloping ceiling, the area up to 60cm outside the height of 1.9m must still be included in the measurement, i.e. the surrounding area where the height is less than 1.9m.
Measuring the primary area (in norwegian)
Measuring rooms with a sloping ceiling (in norwegian)