The home-owners were woken by their smoke alarm in the early hours.
Two fire engines with nine firefighters and six on-call crew were called to the St Saviour property at 3.50am (8 September).
When they arrived a 'fully developed' fire had engulfed the first floor of the home.
The crew managed to knock back the fire before going inside with breathing apparatus and fully extinguishing the fire.
No one was injured.
The fire service says the incident highlights the importance of having a working smoke alarm.
The cause of the fire is still being investigated.

Consultation launched on hate crime legislation
Plans for Fort Regent transformation fall behind
Islanders wanted for 'Humans' project
Extra DFDS sailings planned with bad weather forecast
£100,000 available in 2027 Performance Sport Programme
Public meeting to mark 75 years of Alcoholics Anonymous in Jersey
Four jailed for drug trafficking and money laundering offences
Frank Bruno visits Victoria College