during the 19th century tenements became the predominant type of new housing in scotland's industrial cities, although they were very common in the old town in edinburgh from the 15th century, where they reached ten or eleven storeys and in one case fourteen storeys. built of sandstone or granite, scottish tenements are usually three to five storeys in height, with two to four flats on each floor. (in contrast, industrial cities in england tended to favour "back-to-back" terraces of brick.) scottish tenements are constructed in terraces, and each entrance within a block is referred to as a "close" or "stair"—both referring to the shared passageway to the individual flats. flights of stairs and landings are generally designated common areas, and residents traditionally took turns to sweep clean the floors and, in aberdeen in particular, took turns to make use of shared laundry facilities in the "back green" (garden or yard). it is now more common for cleaning of the common ways to be contracted out through a managing agent or "factor".