The French housing crisis has encouraged Paris estate agents to invent a new type of property, the 'sousplex'. A reverse of the more commonly known duplex, the 'sousplex' consists of a ground and basement level living area and makes use of many former unexploited areas of typical city centre apartment blocks.
However, potential buyers should be aware that many recent conversions are in fact illegal as, under current planning regulations, all living rooms (including bedrooms) are required to have normal height windows, not just a ventilator at pavement level. Whole streets are also designated as 'commercial' where planning consent will not be given for conversion of former boutiques and workshops into living accommodation.
However, because planning departments are notoriously under-staffed, many building conversions go unchecked, or are carried out without planning permission or the agreement of the building co-owners - or occasionally with their connivance. The result is that many owners find they have bought an unsaleable property, unless they can secure retrospective planning consent and the approval of the co-owners at their annual general meeting. Neither are easy to obtain and can not be guaranteed.
Among the advantages cited by promoters of this type of property are lower purchase costs, sometimes 30% less than traditional apartments (but conversion costs can be high); lower taxes as some parts may not be officially designated as living space; and the chance to create vast areas of open-plan living accommodation. They have a particular appeal to fashionable young couples who like entertaining and parents with large families.
As always, professional advice should be sought as to the feasibility and legality of any proposed building conversion, before committing to purchase.