Cornwall Fire and Rescue Service said 11 residents had to be evacuated from the property in Eastborne Road.
Six fire engines from St Austell Mevagissey, Fowey St Dennis and Lostwithiel tackled the blaze.
The building is used as sheltered accommodation.
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Statistics show month of March to be sunnier than average despite a very windy and wintry period of weather in last 24 hours.
Strong winds have been wreaking havoc across our region, affecting roads, trains and ferries and disrupting journeys to work.
As we leave winter behind and re-discover daffodils and longer days, we showcase your shots of West Country spring.