What is Net Usable Area?

Net usable area comprises space functional to the occupier and includes lift lobbies and pantries if the occupier has exclusive use over such spaces. The area occupied by partitions within the premises is considered part of net usable area as these are often a tenant option. Areas occupied by structural columns and other common areas (such as stairwells and vertical ducts) that are not used exclusively by the occupier are omitted.

Source:
http://www.iproperty.com.my/propertymarket/DTZ_GOOC2007.pdf