Six fire crews battled the flames at £1.2 million Aspen House, at Beech Hill, for several hours, but large parts of the home were destroyed.
The fire was accidental, with the cause believed to be an electrical fault with a bathroom light fitting.
Crews estimated that 70 per cent of the roof, half of the second floor and 25 per cent of the first floor had been affected by the fire.
According to neighbours the owner of the house lives in the Stonegate area, and in a cruel twist of fate a new tenant was due to move into the house on Tuesday.
Rupert North and his family have had to temporarily move out of their home, which connects to Aspen House, after it suffered water and smoke damage.
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