A professional group is trying to thrash out a set of rules to help property buyers work out exactly what they are getting for their money. The Hong Kong Institute of Surveyors was meeting last night on a proposal to include balconies and similar features in the saleable area of a flat but to exclude common areas, such as staircases, lift shafts, lobbies and communal toilets. The institute wants developers to adopt saleable area as the basis for selling flats instead of the present practice of using gross floor area. It is working to update the definition of saleable area which has become outdated since set out in 1999. The move follows complaints by buyers who say their actual living space has been shrinking as more common areas are included in the gross floor area. Under the plan, the saleable area of a flat would be the area contained within the enclosing walls measured up to the exterior face of an external wall or the centre line of separating walls between adjoining units. All internal partitions and columns within the flat should be included. The definition would include core saleable area and ancillary saleable area. Core saleable area is the roofed, or interior area, with full headroom capable of full normal occupation. Ancillary saleable area includes cocklofts, bay windows, yards, terraces, gardens, flat roofs, garages, plant rooms and meter rooms. Details of the ancillary saleable area should be listed.