The biggest group of homes in Norwich was built between 1965 and 1982. This is the peak period for asbestos in UK housing. Insulating board, textured coatings and asbestos cement were all in routine use, so original materials are common. Roughly 81.6% of the 69,270 properties here predate the 1999 ban, and the largest group by type is flats and maisonettes at 37.5%. In flats and maisonettes the risk is often in the parts nobody owns individually: service risers, ducting, communal cupboards and ceiling voids, where insulating board and lagging were widely used. Inside a flat, textured coatings and floor tiles are the common ones. The next largest group is terraced houses at 36.8%, where party walls and shared roof spaces mean neighbouring work can disturb material next door. By period, 18.9% were built before 1900, 15.1% between 1919 and 1939 and 18.3% since 2000. None of that tells you whether a particular property contains asbestos; only a survey or a laboratory test can.