Later examples suggest that either French or American buildings were taxed by their height (or number of storeys) to the base of the roof, or that mansards were used to bypass zoning restrictions. This last explanation is the nearest to the truth: a Parisian law had been in place since 1783, restricting the heights of buildings to 20 metres (65 feet). The height was only measured up to the cornice line, making any living space contained in a mansard roof exempt. A 1902 revision of the law permitted building three or even four storeys within such a roof.